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What Is St Elmo’s Fire?

What Is St Elmos Fire

Occasionally, seemingly inexplicable flames or lights can be observed in the night sky, especially near tall objects. These incidents occur throughout history. The phenomenon is known as St Elmo's Fire.

St Elmo's Fire is a meteorological occurrence where pointed tall objects in the atmosphere like church towers and ship masts create an electrical discharge in the form of a blue plasma in a highly charged electrical field. The illuminated plasma is the result of a process called corona discharge.

There are various sources of light forming in the atmosphere that are well-known meteorological phenomena. Examples include occurrences like lightning, the aurora borealis, the green flash during sunsets, and noctilucent clouds in the evenings.

One such event creates a blue flame-like glow at the edge of a relatively sharp object and is called St Elmo's Fire. It often gets mistaken for other natural phenomena like fire or ball lightning, although it is a completely unique occurrence.

This article examines what this phenomenon is, provides a brief history, and explains how it develops in the atmosphere.

What Is St Elmo's Fire?

The word fire, in St Elmo's Fire, can be very deceiving. Although the blue glow that forms as a result of this phenomenon may resemble a blue flame, the process itself has nothing to do with any type of fire.

Before examining how this occurrence is formed, one needs to have a clear definition of what precisely it is first.   

St Elmo's Fire Definition

What Is St Elmos Fire

St Elmo's Fire is a meteorological occurrence where pointed tall objects in the atmosphere like church towers and ship masts create an electrical discharge in the form of a blue plasma in a highly charged electrical field. The illuminated plasma is the result of a process called corona discharge.

The blue glow, whose shape sometimes resembles a form of fire or lightning, is often accompanied by a hissing or buzzing sound. (Very much like the buzzing of neon light, which is basically the same process.)

It was already made clear that there is no relation between the blue glow synonymous with this event & incidents of an actual fire. Although they have similar characteristics, St Elmo's Fire is also not a form of lightning, though it has been mistaken for ball lightning in the past.

The name and history imply that this phenomenon mostly applies to maritime-related activities (more on that in the next section.) It has been shown that, however, that St Elmo's Fire can occur anywhere over land as well, If all the necessary components are in place.

As it is clearly a unique occurrence, a thorough explanation will be needed to understand how this phenomenon occurs. We will address this issue shortly, but first, a short history that will clarify the name and origin of the name, St Elmo's Fire.

A Short History Of St Elmo's Fire

Some of the first and oldest accounts of this phenomenon recorded were by sailor over the last few centuries that observed the strange glow at the top of their sailing ship's masts.

Saint Erasmus

The word "St Emo" refers to St Erasmus, a Christian bishop who lived during the Third Century. After his death, he became regarded as the patron saint of sailors.

The appearance of the blue flame-like glow on ships' masts was seen by sailors as a good omen, as they believed it indicated the presence of St Erasmus to guide them through dangerous times at sea. As a result, the blue discharge became known as St Elmo's Fire.

The fact that the phenomenon usually appears near the end of thunderstorms cemented the belief sailors had about it being a good omen since they started to associate with the end of bad and stormy weather.

How Does St Elmo's Fire Occur?

Although it seems to appear out of the blue, a couple of elements need to be in place for this event to occur:

  • A Highly-Charged Electrical Field
  • Narrow And/Or Pointed Pointed Object

In an atmosphere, like the one created during a thunderstorm, friction between particles causes a build-up of particles, leading to an increase in electrons in the air. It creates a highly charged electrical field that stretches all the way to the ground.

Sharp or pointed objects concentrate these highly-charged electrical fields, creating a discharge where air molecules get torn down to form plasma (as atoms are being stripped of their electrons). This process is better known as a corona discharge.

(A corona discharge is a process through which an electrical discharge causes air to be ionized. Ionized air is just another term for plasma.)

Sharp Object And St Elmo's Fire

During this process, illuminated plasma is created that hovers around the object where the discharge took place and can last for several minutes. Objects can include anything from cathedral towers, ship masts, the tip of an airplane wing, and even the horns of cows.

The light created has a blue or violet color since this is the color that oxygen and nitrogen emit when a discharge takes place in the atmosphere.

This exact same process takes place in neon lights, where the discharge gets controlled to allow the illumination of plasma to continue permanently. It explains why the buzzing sound that accompanies St Elmo's Fire is similar to the sound emitted by neon lights.

Is St Elmo's Fire Dangerous?

There have been few if any reports of people coming in actual contact of being engulfed by St Elmo's Fire. It usually occurs on taller sharp objects like ship's masts and church towers.

Even if a human came in direct contact with this phenomenon, though, they would usually experience no more than a pricking sensation. What is much more dangerous, though, is the type of event that accompanies these conditions.

St Elmo's fire occurs in the same type of electrically charged atmosphere that causes lightning to occur. If you observe the former, it may be an indication that a lightning storm is imminent or nearby. It should serve as a warning to take cover.

Conclusion

If you search the term on Google, St Elmo's Fire usually yields results referring to the 1980's movie with the same name. Unlike the film, it is a very real meteorological event and dates thousands of years back.

As this article explained, the mysterious blue flame-like glow that appears around sharp objects is not as inexplicable as many first-time observers may think. In the most simplistic terms, it is no more than an electrical discharge that creates a body of illuminated plasma.

This post explained what St Elmo's Fire is, how it occurs, and briefly touched on any potential dangers it may pose. 

Never miss out again when another interesting and helpful article is released and stay updated, while also receiving helpful tips & information by simply  clicking on this link .

Until next time, keep your eye on the weather!

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Atmospheric Absorption – Shielding The Planet From Solar Radiation

Atmospheric Absorption

Earth gets bombarded by large amounts of solar radiation every day. It's vital for all life on the planet but is just as deadly. Atmospheric Absorption helps to protect us from its most harmful effects. 

Solar radiation is essential for the continual existence of all life on Earth. If the full amount of solar radiation is allowed to reach the surface unfiltered, though, it will be deadly and cause complete devastation.

A large portion of electromagnetic energy is scattered, refracted, diffused, and reflected by the surface and atmosphere. A significant amount of radiation is also absorbed by the atmosphere, a process called Atmospheric Absorption.

This article examines what atmospheric absorption is, how it occurs, and what parts of solar radiation are affected.

Atmospheric Absorption Definition

From the introduction, it is clear that atmospheric absorption forms a significant and essential part of the way solar radiation gets regulated by the planet. To understand how this process works, atmospheric absorption needs to be more clearly defined.

What Is Atmospheric Absorption?

What Is Atmospheric Absorption

Atmospheric Absorption is the process through which gases and small particles in the atmosphere absorb a large percentage of solar radiation. It protects all lifeforms on the planet from the most harmful effects of the sun's ultraviolet and infrared radiation.

The sun's radiation consists of a wide range of light in the electromagnetic spectrum, from short-wavelength x-rays on the one side to long-wavelength radio waves on the opposite side of the spectrum.

The three most important forms of solar radiation that reach and impact the Earth is:

  • Visible Light 
  • Infrared Light
  • Ultraviolet Light.

Visible light forms roughly half the total amount of solar radiation reaching the atmosphere.

Atmospheric absorption is responsible for a significant portion of this solar radiation not reaching the surface of the planet, specifically infrared and ultraviolet light. 

Solar Spectrum

The Solar Spectrum Showing The Absorption & Transmission Of Different Wavelengths

Of the three primary components that make up solar radiation, visible light is the only one that reaches the planet's surface without any significant amount of absorption or filtration taking place.

In contrast, infrared and ultraviolet light gets subjected to a significant amount of absorption in the atmosphere. In the next section, we will discuss how this takes place.

How Atmospheric Absorption Occurs

The atmosphere absorbs 23 percent of all incoming solar energy. It does so through the ability of specific gases and small particles to absorb different wavelengths of radiation in the solar spectrum.

The regions in the spectrum that travels through the atmosphere without much absorption and reaches the planet's surface relative unaffected are called atmospheric windows. Visible light falls within this region.  

The parts of the electromagnetic spectrum that gets absorbed by the atmosphere are known as absorption bands. Infrared and ultraviolet light are the two biggest sources of radiation fall within this adsorption range.

The three most significant gases responsible for absorbing solar radiation is:

  1. Water Vapor (H₂O)
  2. Carbon Dioxide (CO₂)
  3. Ozone (O₃)

The way in which these gases absorb solar radiation is by a form of energy exchange in which gas molecules turn incoming light energy into heat. As a result, the atmosphere experience a rise in temperature where absorption takes place.   

Carbon Dioxide

Water vapor is responsible for absorbing the largest amount of solar radiation. Combined with carbon dioxide, water moisture is mainly responsible for the abortion of infrared radiation that sits on the side of the electromagnetic scale comprised of longer wavelengths.

The largest concentration of ozone is found in the stratosphere. It is here in the ozone layer that the highest percentage of ultraviolet light gets absorbed (which sits on the side of the electromagnetic scale comprised of shorter wavelengths.)

UV light consists of Ultraviolet-A, Ultraviolet-B, and Ultraviolet-C rays. Of these three, Ultraviolet-C is by far the most dangerous. However, ozone absorbs more than 90 percent of this form of ultraviolet light.

Ozone also absorbs around 50 percent of Ultraviolet-A and 90 percent of Ultraviolet-B radiation. The 10 percent of UV-B that does reach the Earth's surface is enough to still pose a significant threat to human health.


It should be noted, however, that even though the gases mentioned here are responsible for absorbing a large amount of solar radiation (that can be extremely dangerous to all life on Earth), it is not the only source for preventing solar radiation from reaching the surface.

Dust and other small particles are the primary sources responsible for scattering and absorbing the total effective amount of solar radiation. It is through this process that the most significant impact of solar radiation is diminished.

Importance Of Atmospheric Absorption

It should be self-evident from the information already provided in this post just how crucial atmospheric absorption is to the survival of all life on Earth.

To emphasize the importance of this process, two key areas will be highlighted where the absence of atmospheric absorption will be catastrophic to the planet.

1) Ultraviolet Radiation Protection

Almost no Ultraviolet-C light reaches the planet's surface since more than 99 percent gets absorbed by ozone in the atmosphere. UV-C light is the most dangerous form of ultraviolet radiation and can cause severe burns, eye damage, and skin cancer.

Even if only 50 percent of UV-C radiation were allowed to reach the surface, the result would be catastrophic for all life on Earth, making outside exposure to the sun almost impossible. 

(The same applies to Ultraviolet-B radiation, where around 90 percent of this light is blocked by the atmosphere.)

2) Warming Of The Planet's Surface

Infrared Light

Infrared light is responsible for warming the surface of the planet, which is essential for the existence of every biological organism (humans included.)

A fine balance exists between the amount of heat the Earth receives and the amount that gets radiated back into space. A large percentage of IR light gets absorbed by water vapor and carbon dioxide in the atmosphere.

In the absence of this absorption, heat will build up at a much faster rate than it can be expelled, which will make the planet uninhabitable in a very short space of time.

Everything in this section has already been mentioned throughout this post, but it was worth emphasizing to highlight just how crucial the atmospheric absorption process is.

Conclusion

From this post, it is clear that although it not such a well-known topic, atmospheric absorption forms a crucial part of the Earth's global climate and weather systems.

This article focused on explaining what atmospheric absorption is, how it takes place, and its importance to the planet and all life on it.

Feel free to leave any comments, questions, or suggestions you may have. Your opinion is valued and will be attended to as soon as possible.

Never miss out again when another interesting and helpful article is released and stay updated, while also receiving helpful tips & information by simply  clicking on this link .

Until next time, keep your eye on the weather!

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Canyon Wind: What It Is And How It Forms

Canyon Wind - What It Is And How It Forms

Wind is usually the result of a change in air pressure, with other atmospheric variables also playing a role. Physical changes on the planet's surface can also create specific wind types like a canyon wind.

A canyon wind is an evening wind that occurs when cold canyon walls cool down the surface air above, which flows to the base and down the valley due to the Earth's gravity. It is also a strong low-level wind that forms when air is forced to accelerate in the narrow space between the canyon walls.

Variations on the planet's surface like steep elevations (mountains), valleys, plateaus, and canyons can play a significant part in the formation of weather. One weather element that is especially prone to variations on the surface is wind.

This article will focus on the role canyons (or canyon-like features) play in the formation of a type of wind called a canyon wind. 

A canyon creates a unique environment where not one but two different types of canyon winds can form. This post will examine what they are and how they are formed.   

What Is A Canyon Wind?

As the introduction already eluded to, a canyon's physical attributes allow for the formation of two distinct winds, both of which can fall under the term, canyon wind.

It is, therefore, crucial to have a clear and concise definition of these phenomena before exploring their creation and characteristics in more detail:

Canyon Wind Definition

What Is A Canyon Wind

A canyon wind is an evening wind that occurs when cold canyon walls cool down the surface air above, which flows to the base and down the valley due to the Earth's gravity. It is also a strong low-level wind that forms when air is forced to accelerate in the narrow space between the canyon walls.

From the definition alone, it is already evident that the two types of wind that are the result of an interaction with a canyon are distinct and very different from each other.

The wind that flows down the canyon walls in the evenings is also known as a mountain breeze, which may be more familiar to many readers.

The low-level wind that is the result of air being forced to flow through a confined space between canyon walls is also known as a gap wind.

The best way to gain a clear understanding of both winds is to examine the development and characteristic of each one individually.

Development Of A Canyon Wind (Mountain Breeze)

During the day, the sun heats the floor and slopes (walls) of a canyon. In turn, the heated surface warms up the air directly above it, causing it to expand and rise into the atmosphere. (This phenomenon is often referred to as a valley breeze.)

Mountain Breeze

In the evening, the surface of the canyon walls cools down more rapidly than the surrounding atmosphere. The colder surface cools the air above it, causing it to contract and become denser as its temperature continues to drop.

The dense cold air is heavier than the surrounding atmosphere and starts to flow down the slopes to the canyon floor. The resulting airflow is called a canyon wind (often better known as a mountain breeze.)

Canyon winds can be quite strong due to the steep gradient of canyon walls. Where the canyon winds from the two opposing walls converge at the bottom, they can combine and follow the downward slope of the canyon floor as a single strong air current. 

Development Of A Canyon Wind (Gap Wind)

As discussed earlier, a canyon wind in the form of a mountain breeze is not the only form of canyon wind that occurs.

When a low-level wind encounters a geological obstacle like a mountain, it needs to find a way past it. Since this type of wind is usually only a few hundred meters high, it is not always possible to maintain momentum and mass by flowing over the mountain.

When it encounters a gap in the mountain, like a canyon, the wind is forced to funnel through the relatively narrow channel created by the canyon. To maintain mass and momentum, air needs to accelerate, producing strong winds in the process.

Gap Wind

The channeled wind that forms as a result of the funneling of air through a narrow space is called a canyon wind (sometimes better known as a gap.)

These types of canyon winds can reach high velocities of up to 93 km/h (58 mph). The speeds were thought to be at their strongest in the narrowest part of the canyon (called the Venturi Effect).

Recent studies concluded that this not the case since canyons are open at the top, allowing air pressure to force wind to rise over the mountain. They determined that the greatest wind speeds occur at the exit of a gap in the mountain (the canyon mouth.)

This type of canyon wind is not just limited to natural geological phenomena but also man-made structures.

Urban Canyon Effect

In densely populated urban areas, specifically city centers with tall buildings flanking city streets, a phenomenon identical to a canyon wind (gap wind) occurs quite frequently.

When low-level winds encounter a city center with its "wall of buildings," the narrow opening provided by streets acts as a canyon. Similar to canyons, the wind accelerates as it is channeled through this small gap, creating what is called an urban street canyon.

This urban canyon effect occurs when the wind hits the densely grouped buildings at a parallel angle, where the streets that are running in the same direction as the wind act as an escape route through which the wind can be funneled.

The urban canyon effect forms part of a broader meteorological phenomenon that occurs in large metropolitan areas called an Urban Heat Island.

Conclusion

What is clear from this article is that geological structures on the Earth's surface can play a huge role in the formation and modification of air movement. In the case of canyon winds, these structures can even result in more than one type of wind.

Canyon winds are unique since their structure allows them to create two distinctly different types of winds with their own characteristics. Also known as mountain breezes & gap winds, these forms of canyon winds can occur in similar environments under different names.

This article focused on the two types of canyon winds, how they develop, and also highlighted how urban environments could recreate the effect of certain canyon winds.

Never miss out again when another interesting and helpful article is released and stay updated, while also receiving helpful tips & information by simply  clicking on this link .

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Ephemeral Stream: What It Is And How It Occurs

Ephemeral-Stream - What It Is And How It Occurs

All waterways play a crucial role in providing an adequate supply of water to animals, humans, as well as vegetation. It even applies to the seemingly insignificant and little-known ephemeral stream.

An ephemeral stream is a temporary stream that only flows for a brief period as a direct result of precipitation, which mainly occurs in arid and semi-arid regions where rainfall occurs infrequently. It differs from intermittent streams by not having a clearly defined physical channel or bed.

Not all rivers and streams continuously flow throughout the year. Some of them are seasonal, and some only flow during specific events. No matter what their size or frequency, they all form part of the Water Cycle that distributes and cycles water around the planet.

One such temporary stream is called an ephemeral stream. It does not flow often and only for a short duration during specific occurrences. Yet, it is still just as an important source of water as any extensive permanent river system. 

This post examines what an ephemeral stream is, how it forms, and how it differs from other types of streams and rivers.

Ephemeral Stream Definition

Most major river systems and larger streams flow throughout the year, meaning they are perennial. (Like the Rhine in Europe, the Amazon in South America, and the Nile in Africa.) An ephemeral stream, though, is not only transitory but is not even a seasonal occurrence.

To be able to describe how and why this type of stream form, one needs to gain a clear understanding first of what precisely an ephemeral stream is:

What Is An Ephemeral Stream?

What Is An Ephemeral Stream

An ephemeral stream is a temporary stream that only flows for a brief period as a direct result of precipitation. It occurs mainly in arid and semi-arid regions where rainfall occurs infrequently. It differs from intermittent streams by not having a clearly defined physical channel or bed.

The word "ephemeral" is derived from the 16th Century Greek word "ephēmeros," which aptly means "lasting for a very short time." And it is the brief occurrence of an ephemeral stream that is its most defining characteristic.

Since these streams occur for such a brief period, it does not have the time to carve out a deep and wide channel, as is the case with a perennial river. It also occurs in predominantly dry regions, where the groundwater table forms much deeper below the surface.

As a result of these two factors, ephemeral streams occur above the groundwater table, compared to more permanent streams and rivers, which riverbeds lie below the water table. The significance of the groundwater table height will become clear in a later section.

How Ephemeral Streams Formed

In arid or semi-arid regions, precipitation occurs very infrequently. As a result, when a large enough amount of rainfall does occur, it often forms a temporary stream on the surface.

The stream can create a new path or follow an existing channel (also called a dry wash) established by previous occurrences of ephemeral streams.

The paths these streams follow can link up with larger networks of intermittent or perennial streams and rivers.

Dry Stream Bed

They can also continue to flow for a short distance before evaporating completely without reaching any significant point or being absorbed into the soil to form groundwater.

Ephemeral streams flow for a limited time and dry up quickly, only leaving a dry stream bed behind. These dried-up channels are sometimes more accurately described as arroyos, which are synonymous with the arid and semi-arid areas where ephemeral streams occur. 

It is important to note that the ephemeral stream and the channel (arroyo) it flows in are not the same things. The stream itself is the actual flow of water that is transitory, while the channel it flows in remains a permanent fixture of the landscape.

Importance Of Ephemeral Streams

It is only natural to conclude that ephemeral streams play an insignificant role in contributing to the Water Cycle and have any other beneficial influences on the environment. Such a conclusion can not be further from the truth.

These streams play an essential role in supplying fresh and maintaining existing resources in at least three different ways:

1) Fresh Water Supply To Perennial Water Networks

Even though ephemeral streams only flow during or after a spell of rain, the combination and frequency of these streams have a huge impact. In fact, they contribute the vast majority of freshwater to the entire river network in arid and semi-arid regions.

For example, 95% of all streams in the Arizona Dessert are seasonal, of which a substantial amount are ephemeral. Even in wetter regions with frequent rainfall, it is estimated that more than 50% of the total stream network consists of temporary streams.

2) Supply Of Fresh Sediment To  Downstream Regions

Fresh Sediment Supply

During extended dry spells, dried-up stream beds (arroyos) builds up a layer of soil, which nutrient content hasn't been depleted by vegetation growth. 

The organic matter created by dead animals and insects, as well as the remains of dead plants, also accumulate in arroyos, further enriching the nutrient content of the soil.

When a spell of rain causes an ephemeral stream to flow, it carries this nutrient-rich soil downstream, where it gets deposited on riverbanks and the surrounding areas, replenishing the land with much-needed fresh sediment.

3) Maintenance And Replenishment Of Groundwater Tables

As the arid and semi-arid regions, where ephemeral stream occurs, don't contain much moisture, the groundwater tables are situated much further below the surface than in wetter areas with an abundance of rain.

When a substantial amount of rain falls, it allows ephemeral streams to contain a large enough volume of water to have some of it absorbed by the ground to replenish its deep water tables.

It can also flow far enough to connect with more permanent (perennial) river networks downstream. It not only supplies these systems with additional water but also assists in maintaining and replenishing their groundwater tables as well.

The Difference Between Ephemeral And Intermittent Streams

Some confusion exists among observers about the difference between ephemeral streams and intermittent streams since they are both regarded as temporary streams.

Ephemeral streams have already been clearly defined as temporary streams that only flow as a direct result of precipitation. The depth of their groundwater tables also means that they can't access this water source to sustain their flow in any way.

Difference Between Ephemeral And Intermittent Streams

Intermittent streams, however, differ in more than one way. They are often seasonal, meaning that although they don't flow throughout the year, they receive a steady supply of water during the rainy season, which allows them to flow for sustained periods.

They also have deeper and more prominently defined river beds, combined with shallower groundwater tables as a result of the availability of more water. It allows the river beds to lie below the water table, allowing them to access groundwater to sustain their flow.

Conclusion

What became clear through this article is how a seemingly insignificant occurrence can play a significant role in a much more extensive network.

An ephemeral stream is not only temporary but only flows for a brief period during or after a spell of rain. Yet, in many regions, they account for the vast majority of water supply to major river networks, enabling them to flow throughout the year.

This article explained what an ephemeral stream is, how it forms, and its importance to larger, more perennial water networks. It also addressed and clarified the difference between an ephemeral and intermittent stream.

Never miss out again when another interesting and helpful article is released and stay updated, while also receiving helpful tips & information by simply  clicking on this link .

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Cap Clouds – What They Are And How They Differ From Lenticular Clouds

Cap Cloud - What It Is And How It Differs From Lenticular Clouds

The majority of clouds develop as a result of different atmospheric variables like heat, wind & moisture. Some, though, form as a result of variations on the Earth's surface. Cap clouds are one such case.

A cloud or pileus cloud is a stationary orographic cloud that forms over the peak of a mountain when moist air is forced up the windward slopes, and condensation occurs as it flows over the top. Unlike lenticular clouds, they form directly over a mountain or high hilltop and have a dome-shaped form.

Variations on the planet's surface influence a variety of meteorological occurrences like wind, temperature, and, yes, cloud formations. Especially elevations and dips on the surface play a significant role in the development of certain clouds. 

One type of cloud that is a direct result of the physical elevation in terrain is called a cap cloud. In this post, we look at what cap clouds are, how they form, and how they differ from the more familiar lenticular clouds.

Cap Cloud Definition

As mentioned in the introduction, a cap cloud is the result of a change in physical terrain, but this is not the only factor at play in the formation of this cloud system.

Before looking into how a cap cloud is formed, one must first define what precisely it is and describe its characteristics in more detail: 

What Is A Cap Cloud?

What Is A Cap Cloud

A cloud or pileus cloud is a stationary orographic cloud that forms over the peak of a mountain when moist air is forced up the windward slopes, and condensation occurs as it flows over the top. Unlike lenticular clouds, they form directly over a mountain or high hilltop and have a dome-shaped form.

This cloud is characterized by its unique mushroom or upside-down saucer shape and can always be found over the top or above a mountain peak.

It is not that uncommon to see two cap clouds on top of each other, hovering over the same mountain top. It occurs typically when a layer of dryer air separates two layers of moist air.

How Cap Clouds Form

Cap clouds form as a result of orographic cooling (which is part of the Orographic Effect). As prevailing winds push moist air against a raised terrain like a mountain, it forces the layer of air to rise against the slopes.

As the air rises, it starts to cool down. It continues to cool down until it reaches dew point, and condensation takes place near the top of the mountain. As a result, the air flowing over the mountain top creates the flat, dome-shaped cloud that is the trademark of a cap cloud.

The raised terrain does not only cause the air to rise on the windward side of the mountain, but as it starts to descend down the leeward slopes, it also creates a wave in the airflow. And it is here where lenticular clouds come into play.

Lenticular Cloud Definition

The wave formed in the wake of the air lifted over an elevated terrain forms the foundation for the occurrence of lenticular clouds.

As with cap clouds, one first needs to get a clear understanding of the definition of a lenticular cloud before looking into how these clouds develop:

What Is A Lenticular Cloud?

What Is A Lenticular Cloud

A lenticular cloud, characterized by its saucer-like shape, is a stationary cloud that forms in the troposphere on the leeward side of a mountain. It forms on the crest of a wave that results from air forced to lift over raised terrain. Its alignment is perpendicular to the direction of air movement.

As mentioned in the description, lenticular clouds form at a high altitude in the troposphere. This is mainly due to the elevated terrain, specifically mountains, that is responsible for creating the conditions favoring the formation of these clouds. 

A few elements need to be in place to form the ideal conditions for lenticular clouds to occur. The creation of wave movement on the leeward side of a raised terrain is the crucial element in the formation of these clouds.

The saucer or lens-like shape is another unique characteristic of lenticular clouds. Since it does not appear close to the surface, it is not often visible from the ground. As a result, it is often mistaken for a UFO (Unidentified Flying Object) or another artificial object.

The layered (pancake) shape of the cloud is the result of multiple layers of cold air reaching dew point at the crest of downwind waves. The crucial role these downward waves play in the formation of lenticular clouds will become evident in the next section.

How Lenticular Clouds Form

For a lenticular cloud to form, three elements need to be present and in place:

  • Adequate Moisture In The Air
  • Prevailing Wind
  • Formation Of A Wave In The Air Movement On The Leeward Side Of A Mountain

As mentioned earlier, it is this wave of air that is primarily responsible for the formation of a lenticular cloud.

After the formation of a cap cloud, the air which lifted on the windward side of a raised terrain dips on the leeward side. More importantly, it creates a continuous wave in the air moving downwind.

How Lenticular Clouds Form

The wave consists of a series of crests and troughs continuing downwind. When moist air reaches the crest of a wave and the temperature drops below dew point, condensation takes place, which allows for the development of a lenticular cloud.

When the prevailing wind persists, the crests and troughs in the wave of air continue to form downwind, which can result in a series of lenticular clouds to form. These formations are better known as wave clouds.

The clouds seem to remain stationary, but there is a constant flow of air through them. The reason they "stay in place" is that the air dips below dew point at the crest of the wave, allowing the cloud to form. When the wave dips down, it evaporates as the air warms up.

Difference Between Cap Clouds & Lenticular Clouds

What will have become evident during the description of cap and lenticular clouds is that their formation is almost identical. The only difference is that a lenticular cloud forms on the wave of air created due to forced elevation on the leeward side of a mountain.

Several articles and papers clearly state that cap clouds are actually lenticular clouds due to the almost identical formation process and similar cloud shape. Technically, this statement is correct, and a cap cloud can be classified as a lenticular cloud.

However, from a practical standpoint, and when described in layman's terms, there are subtle but significant differences between the two that can be summarized as follows: 

  • While cap clouds occur directly over a mountain peak, lenticular clouds usually form on the leeward side of the mountain.
  • Cap clouds have a flat, dome-shaped form, while lenticular clouds have a layered or stacked shape in the form of a lens or saucer.

As already stated, these are subtle but significant differences.

Conclusion

It is clear that there can be some confusion when discussing cap clouds and lenticular clouds and why they are often seen as the same type of formation. This post managed to highlight the small but notable differences between the two.

And that was the aim of this article: To explain what cap clouds are and how they form, and how they differ from lenticular clouds in formation and shape.

Never miss out again when another interesting and helpful article is released and stay updated, while also receiving helpful tips & information by simply  clicking on this link .

Until next time, keep your eye on the weather!

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The Adiabatic Process: What It Is And How It Occurs

Adiabatic Process-What It Is And How It Occurs

Air pressure plays a vital role in meteorology and has a significant impact on the majority of weather events. The adiabatic process focuses on air pressure's role in an isolated body of air.

In meteorology, the adiabatic process primarily describes the heating or cooling of a body of air without any energy exchanged with the surrounding atmosphere. The temperature changes occur due to the air pocket's compression or expansion as a result of pressure changes in the surrounding air.

Think of the internal combustion engine (ICE) used in traditional motor vehicles. Without the air pressure created in the combustion chamber to drive the piston inside a cylinder, the ICE will not be able to operate.

Similarly, the steam engine, which was widely used during the early stage of the Industrial Revolution, operates on the same principle. Heat is applied to a confined chamber, causing moist air inside to expand, which in turn forces cylinders to move up and down.

The three factors that play an essential role in both these processes are heat, air pressure, and a confined body of air. And it is these three factors that also create a similar process in meteorology. It is called the adiabatic process.

As already shown, the adiabatic process is used in a variety of different disciplines. However, this post will focus exclusively on the adiabatic process as it applies to meteorology.

Adiabatic Process Definition

During the introduction, you already received plenty of clues as to what the adiabatic process entail and was probably able to form a vague idea of its definition.

It is essential, however, to get a clear and concise definition of what precisely the adiabatic process is before examining how this phenomenon takes place.

What Is The Adiabatic Process?

What Is The Adiabatic Process

In meteorology, the adiabatic process primarily describes the heating or cooling of a body of air without any energy exchanged with the surrounding atmosphere. The temperature changes occur due to the air pocket's compression or expansion as a result of pressure changes in the surrounding air.

One of the most vital characteristics of the adiabatic process to highlight is the fact that the process takes place in relative isolation. It simply means that no mixing of air takes place between the body of air and the surrounding atmosphere.

There is a second important characteristic of the adiabatic process in meteorology. And this is that it occurs as a result of the surrounding atmosphere's pressure on the air pocket, specifically in adiabatic cooling and heating.

Now that it has been established that the heating and cooling of a body of air is one of the primary impacts of the adiabatic process, the focus should now be on how these cooling and heating processes take place.

Adiabatic Cooling

Adiabatic cooling is a natural occurrence that takes place in the lower atmosphere and is primarily due to a change in altitude. Usually, the altitude change occurs through one of two processes. These two processes are:

  1. The Heating Of A Layer Of Air At The Surface
  2. Forced Elevation Due To A Rise In Geographical Terrain

1) The Heating Of A Layer Of Air At The Surface

Adiabatic Heating

When solar radiation heats the Earth's surface, it also warms the air above it. The warm body of air is less dense (and lighter) than the surrounding air and starts to rise. As it gains altitude, it continues to move into areas with less density, causing it to expand even further.

Any body of air contains a large number of molecules that vibrate and bounce off each other. The closer these molecules are to each other, the quicker they vibrate and collide with each other. We observe this as a rise in temperature. 

In this case, however, the body of air expands as it gains altitude, where the atmosphere has less air pressure. It means the molecules move further away from each other, becoming less energetic with fewer collisions occurring, resulting in a drop in temperature.

2) Forced Elevation Due To A Rise In Geographical Terrain

Sometimes adiabatic cooling is not the result of the heating of a surface. When prevailing winds (like a sea breeze blowing inland) are present, a layer of air is moved horizontally but sometimes encounters a raised terrain like a mountain or large hillside.

As a result, the layer of air is forced to rise against the mountain slopes. As the altitude increases, the atmospheric pressure becomes less, allowing the air pocket to expand and cool down in the same way a body of warm air rising from the surface would.

This form of adiabatic cooling is also known as orographic cooling, which forms part of the Orographic Effect. To find out more about this phenomenon and how it occurs, you can read the in-depth article here.


The rate at which temperature drops as altitude increases is called the adiabatic lapse rate. The amount of moisture in the air plays a role at the rate at which temperature decreases and can be divided into the:

Dry Adiabatic Lapse Rate: When there is little or no moisture present in the air parcel, it will cool at an average rate of 10° Celsius per 1 000 meters (5.6° Fahrenheit / 1 000 Feet).

Wet (Moist) Adiabatic Lapse Rate: When a substantial amount of moisture is present in a body of air that is rising,  it will cool at an average rate of 5° Celsius per 1 000 meters (3.2° Fahrenheit / 1 000 Feet).

Please note that these figures are just average lapse rates and will vary according to more specific atmospheric conditions.

Adiabatic Heating

The adiabatic process takes place in reverse during an occurrence of adiabatic heating.

When a body of air at higher altitudes starts sinking to the ground, it gets subjected to increased atmospheric pressure as it moves closer to the planet's surface. The increased pressure causes the air parcel to compress and shrink in size.

Orographic Heating

As already discussed, when a body of air contracts, the molecules inside get energized as it starts to vibrate more quickly and collide with each other at an accelerated pace. This process manifests as a rise in temperature.

One example of adiabatic heating occurs during a heat burst when a layer of cold, dry air drops to the ground from a high altitude in the wake of a dissipating thundercloud.

Another example is part of the Orographic Effect as cold, dry air drops down the slopes on the leeward side of a mountain.

Conclusion

The adiabatic process plays a vital role in many fields and disciplines. It also has a significant role to play in several meteorological occurrences.

In this post, we focused on adiabatic heating and cooling and illustrated how they could impact the weather without any energy exchange with external elements like solar radiation, wind, and moisture.

The main goal of this article was to explain the adiabatic process, how it occurs and highlighted some examples of this phenomenon.

Never miss out again when another interesting and helpful article is released and stay updated, while also receiving helpful tips & information by simply  clicking on this link .

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The Hottest And Coldest Time Of The Day – When They Occur And Why

Hottest Time Of The Day - When Is It And Why

A common misconception exists that the hottest time of the day occurs during midday, while the coldest time occurs at midnight. However, both events take place much later than one might imagine.

The hottest time of the day typically occurs 3 to 5 hours after noon (when the Sun is at its highest point in the sky), while the coldest time of the day occurs within an hour after sunrise when the sun's radiation is still too weak to surpass the Earth's rate of emitting heat into the atmosphere.

It only makes sense to reason that the hottest time of the day occurs at midday while the Earth receives the most solar radiation, while the coldest time occurs at midnight when the sun is on the opposite side of the planet. But actually, both events occur much later.

This does not seem to make sense since the Earth receives the most amount of solar radiation from the sun around noon (depending on your location and the time of year.) 

Similarly, the surface will keep on cooling down during the night until sunrise, when it starts to receive sunlight and begins warming up. It is natural to reason, therefore, that the coldest time of the day will be just before sunrise. But this is not the case.

This article examines when the warmest and coldest part of the day is and why they occur at these different times. It also looks at the various factors involved in these occurrences.

Hottest Time Of The Day

As already mentioned, the Earth's surface receives the most amount of solar radiation around noon, yet this is not the part of the day that is the warmest.

Before we look into why this occurs, it is important to define a clear definition first of when precisely the hottest part of the day is:

What Is The Hottest Time Of The Day?

Hottest Time Of The Day

The hottest time of the day occurs between 3 pm and 4:30 pm, 3-5 hours after noon (when the sun is at its highest point in the sky). This delay is due to the Earth's surface receiving and absorbing heat at a higher rate than it can radiate until mid to late afternoon, when the process reverses.

Although this summary is an accurate average to use to judge when a day will be at its warmest, a couple of factors can cause the actual peak temperature to occur earlier or later in the afternoon.

Weather elements such as cloud cover and wind can have a significant impact on peak daily temperatures. Geographical location also has an effect, where inland regions can reach their highest temperatures of the day much later in the afternoon than coastal areas.

Why The Hottest Time Of Day Occur In The Afternoon

Although the sun is at its highest point in the sky and the Earth receives the most amount of solar radiation around noon, we now know that the day's highest temperature does not occur until around 3 pm. This delay is also known as Thermal Response

Surface Radiation

Thermal response occurs as follows: After noon, even though the sun's radiation starts to drop, the Earth retains much of its heat while still receiving solar radiation. It means the heat building at the surface is higher than that which the planet can radiate away. 

As a result, the temperature continues to rise until the solar radiation is weak enough for the Earth's ability to radiate heat back into the atmosphere, becomes greater than the radiation it receives. And this occurs between 3 pm and 4:30.

Coldest Time of the Day

Like the hottest time of the day, the coldest time of the day occurs much later than one might expect. What makes it even more confusing is the fact that weather forecasters often refer to daily lows that will be experienced "during the evening."

It is statements like these that back up the common belief that the coolest time of day should occur during the night. As much as this type of thinking seems to make sense, it is not accurate at all.

As is the case with the warmest time, it is important to define when precisely the coldest time of day is first before we delve into explaining why and how this takes place:

The Coldest Time of the Day

Coldest Time Of The Day

The coldest time of the day occurs approximately an hour or more after sunrise. It occurs when the sun's radiation is still too weak to warm the planet's surface at a higher pace than the Earth's rate of emitting heat away from the surface into the atmosphere.

This may not seem to make sense at first since solar radiation is the primary source of heat and light to the Earth every day.

Take into consideration, though, that when we perceive the sun to rise on the horizon, it is still 6 degrees below the horizon (aka twilight). The atmosphere can bend light like a lens, making it appear that we receive sunlight when no actual solar radiation is yet present.

Depending on your location and time of the year, after sunrise, it will also still take the sun between 3 and 8 hours to reach its highest point in the sky and the Earth to receive maximum solar radiation after sunset.

Although these are all contributing factors, the main reason for the coldest time of the day involves the same factors responsible for the warmest part of the day, which we will address in the next section.

Why The Coldest Time Of Day Occur After Sunrise

After the hottest time of the day, which occurs around 3 pm, the Earth continues to radiate heat out into the atmosphere at an accelerated pace. At the same time, solar radiation decreases until completely disappearing around sunset.

The planet's surface continues to cool down as it radiates heat throughout the night. After sunrise, the ground starts to receive solar radiation, but it is still too weak to counteract the rate at which the surface continues to cool down as it radiates heat into the atmosphere.

Solar Radiation

The coldest time of the day occurs once the speed at which the Earth radiates heat is no longer greater than the incoming solar radiation, and the ground starts to warm up. As already stated, this occurs some time after sunrise. 

The exact time the coldest stage of the day takes place depends on atmospheric conditions, as well as the location and the time of the year.

Conclusion

Although it may not have made sense in the beginning, it should now be clear why the hottest and coldest times of the day occur when they do. It also explained why the delay between the period of maximum solar radiation and the hottest time of the day takes place.

This delay occurs on a seasonal basis as well. The warmest and coldest days of the year (and the hottest and coldest months) are based on the same principle. To find out more about these occurrences, you can find the in-depth article here.  

This article aimed to examine when the warmest and coldest part of the day is and why they occur at these times. It also looked at the various factors involved in these occurrences.

Never miss out again when another interesting and helpful article is released and stay updated, while also receiving helpful tips & information by simply  clicking on this link .

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Huayco: What It Is And How It Is Caused

Huayco - What It Is And How It Is Caused

Avalanches are well-known occurrences that can cause devastation in snow-covered mountainous regions. In the Tropics, though, a weather phenomenon known as a huayco can be just as devastating.

Huayco is the Andean term used to describe the flash flooding and accompanying mudslides that occur in the Peruvian region of South America due to heavy torrential rains. It originates high in Peru's mountainous regions and is closely related to the weather produced by the El Niño phenomenon.

Regions in and around the Tropics get subjected to large amounts of rainfalls throughout the year. These include areas like the Caribbean, Southeast Asia, Central & South America, as well as the mountainous terrain of Asia. It can have deadly and devastating occurrences.

Due to the heavy torrential rain, flash flooding and mudslides occur quite frequently in these areas, especially in the high mountainous terrain of Peru. These events that are so synonymous with this part of the world are more commonly referred to as a huayco.

This post explores what a huayco is, how it gets formed, and its potentially devastating effect on its surroundings.

What Is A Huayco?

As you might have already concluded, a huayco is a mudslide accompanied by flash flooding, which is the result of heavy rains in the mountains of Peru. It sounds simple enough, but there are, in fact, many more factors at work to create this event.

Before looking at the different mechanisms at work in the formation of this event, though, one first needs a concise formal definition of what precisely a huayco is:

Huayco Definition

What Is A Huayco

Huayco is the term used to describe the flash flooding and accompanying mudslides that occur in the Peruvian region of South America as a result of heavy torrential rains. It originates high in Peru's mountainous regions and is closely related to the weather produced by the El Niño phenomenon.

The weather may be the impetus that sets the process in motion but cannot act on its own. The moist, soft soil covering the ground surface, combined with the gravitational force of the steep mountain slopes, largely contributes to the development of a huayco.

In the next section, we will briefly look at the meaning of the term "huayco" and its origins before continuing to explore the formation of this occurrence.

Meaning And Origin Of The Term, Huayco

A huayco is also known as a huaico. When you look at the origin and translation of both these terms, it will become clear how accurately they describe the characteristics of this specific phenomenon.

The word huayco is derived from the Quechuan word, wayqu. The Quechuan language is spoken by the Quechua people living in the Andes region of Peru. The term huayco translates to either "valley" or "depth."

The word, huaico, has a Spanish origin (the most widely spoken language in Peru.) It translates to "avalanche," a phenomenon that shares many characteristics with a huaico.

What Causes A Huayco

The Tropics, where Peru is situated, already receives a large amount of rainfall throughout the year. Occasionally, though, a weather phenomenon called El Niño causes the region to receive an abnormally high percentage of precipitation.

In short, an El Niño occurs when the warm waters of the Pacific Ocean that would normally travel west and accumulate at the coast of Southeast Asia are forced to flow in an easterly direction and build up against the northwestern coastline of South America.

(You can learn more about the formation and characteristics of El Niño in this article.)

The moisture-rich water that builds up against the South American coast results in the largescale formation of rainclouds, which leads to a significant increase in precipitation in regions like Peru.

Torrential Rain

The increased rainfall causes riverbanks to overflow and runoff areas to exceed their boundaries. This leads to flash flooding over parts of the mountainous terrain in the land.

The dry mountain slopes of the Andes in southern Peru have little or no vegetation cover. Combined with heavy deposits of soil, they are left vulnerable and exposed to extreme weather elements. 

During an El Niño event, water from burst river banks and dried-up runoff areas rush down the mountain slopes while picking up the loose dry soil on the ground. It continues to race down the mountain, gathering even more soil until it starts turning into a dense mudslide.

The sheer momentum and size of the mudslide allow it to pick up objects like rocks and tree trunks, creating a potentially devastating and deadly force capable of wiping out almost anything in its path. 

It is this deadly combination of mud, rock, trees (and other objects mixed in) that can completely overwhelm and cover vegetation and small villages at the bottom of the mountain slopes. (More on the impact and effects of a huayco in the next section.)

Contributing Factors To Huayco Formation

Although they have already been mentioned in passing, three main contributing factors help to create very favorable conditions for a huayco to occur in the Peruvian region of South America:

  1. Location of Peru
  2. Climate of Peru
  3. Geography of Peru

Although none of these factors cause a huayco by themselves, each one contributes and combined, they create a very favorable environment for the occurrence of this event.

1) Location of Peru

Peru is situated in the Tropics, just south of the Equator. The western part of the country borders the west coast of South America, which makes it highly susceptible to the weather that occurs over the Pacific Ocean (including the El Niño Effect.)

To the east, the Andes Mountains raise the terrain where higher rainfall creates lush vegetation that forms part of the Amazon Rain Forest.

2) Climate of Peru

Since Peru experience a tropical climate, it is subjected to large amounts of rainfall throughout the year, especially in the mountainous region to the east.

However, the influence of the Pacific Ocean to the east creates a dryer climate, while the Andes Mountains raise the terrain, creating wet & rainy weather conditions to the east of the country.

It is the contrast between the dry low-lying west and elevated east with its higher rainfall that creates a favorable environment for a huayco to develop.

3) Geography of Peru

Essentially, Peru can be broken up into three geological regions:

  • The Amazon Rain Forest
  • The Highlands
  • The Coast

The Amazon Rain Forest forms the northeastern border of Peru. Although it forms the largest region in Peru (59%), only 12% of the population lives in this region. The relatively flat landscape is covered with dense bush and trees that are so synonymous with the Amazon.

The Highlands mainly consists of the Andes Mountains with its peaks and valleys, reaching a maximum height of 6 768 meters (22 204 feet). It occupies 36% of the land, and 30% of the country's population lives in this area.

The Coast occupies the smallest part of the country (11%), yet the largest part of the population (52%) lives on this relatively small strip of coastal land. The dry yet fertile piece of land extends from the ocean to the foothills of the Andes Mountains.

From the geographical layout of the country, it is clear to see how heavy rainfalls originating in the Andes mountains can trigger a huayco as water rush down the slopes and picks up the dry fertile ground and turn into devastating mudslides.

Effects Of A Huayco

The impact of a huayco can and usually is devastating. The widespread damage and injury (and in most cases, loss of life) of largescale mudslides have already been well documented and covered in the mainstream media.

To give you an indication of the sheer size and power of a mudslide, the following list of characteristics will provide some perspective:

  • Flash flooding can trigger one or multiple mudslides at a time. 
  • They vary in size, but a typical big mudslide can be 300 meters (984 feet) wide, 50 meters (164 feet) thick, and 1 600 meters (1 000 feet) long.
  • Mudslides travel downhill at around 80 km/h (50 mph) but can reach speeds of up to 322 km/h (200 mph) on steep slopes.
  • One of the most dangerous aspects of a mudslide is its unpredictability. It can occur suddenly and without warning, leaving little chance to get out of its way. 

From these characteristics, it is clear to see just how devastating a mudslide can be. The following are only a summary of the most significant types of impact a huayco can have:

1) Infrastructure Damage And Destruction

Infrastructure Damage

The sheer speed and size with which a huayco can strike any area will cause either damage or create complete destruction on a broad scale, depending on the size of the mudslide.

It can bury entire villages under meters of mud and completely destroy roads and bridges. Power lines, railroads, and other forms of information can also get washed away in a matter of minutes.

2) Injuries And Fatalities

Many villages in Peru are situated at the bottom mountain slopes. It makes them especially exposed and vulnerable to a huayco. When a mudslide does occur, it can bury an entire village, as already mentioned.

It usually leads to dozens of fatalities, with hundreds of people left injured and displaced. This is just the scenario for a single small village. When a more extensive region and more communities get affected, this number can easily more than double.

3) Loss Of Crops And Livestock

At the bottom of a slope, a mudslide can quickly spread over large areas. These include large fields of crops that are easily destroyed and can also lead to entire herds of livestock being killed off in minutes.

Since many villages live off the land and rely on their crops and livestock for survival, this can have a severe impact and leave people without food for undetermined periods.

4) Disruption Of Water Supply

Water supply and treatment facilities are also adversely affected by mudslides. Reservoirs can get damaged or destroyed. Even if they do not get demolished, the water of dams and water treatment facilities are polluted with contaminants they carry with them.

Water is the lifeblood of any community, and without it, villages and towns in affected areas will suffer and not be able to endure indefinitely.

5) Economic Cost

It should already be evident from the damage and destruction just described, but the economic impact of strong mudslides on the country is severe. It can quickly run into billions of dollars of damage.

One can easily see how a series of these events in quick succession can put a region and the entire country under extreme financial pressure.

Conclusion

Although mudslides occur all over the world, the conditions that create a huayco in the Peruvian region are quite unique, as was illustrated throughout this post.

This article clearly illustrated what a huayco is and how it develops. It also looked at its defining characteristics and impact on the areas it affects as well as human life.

Never miss out again when another interesting and helpful article is released and stay updated, while also receiving helpful tips & information by simply  clicking on this link .

Until next time, keep your eye on the weather!

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Heat Burst: What It Is And How It Forms

Heat Burst-What It Is And How It Forms

On rare occasions during a warm summer, one might get caught off guard by a sudden gust of warm, dry wind, seemingly appearing from nowhere. This meteorological phenomenon is known as a heat burst.

A heat burst is a rare meteorological phenomenon defined by strong gusts of dry winds accompanied by a sudden and significant rise in temperature. This phenomenon typically occurs during the summer months and on warm days during the evening in the wake of a dissipating thunderstorm.

It is not uncommon for some of the most extreme and violent weather events one will ever experience to stem from larger storm systems, specifically those involving thunderstorms.

The subject of this post is yet another example of the "byproduct" of a thunderstorm. Unlike most other weather events involving these storms, though, it is not characterized by cold or wet weather. A heat burst is a rare occurrence with unique characteristics.    

This article examines what a heat burst is, how it gets formed, and also takes a look at it its specific features.

Heat Burst Definition

The introduction already gave away some hints of the makeup of this weather event and its formation. What precisely it is and how it develops will shortly be discussed in detail. 

Before delving in, though, it is imperative to provide a more formal and concise definition of a heat burst to provide a solid foundation to work from:  

What Is A Heat Burst?

What Is A Heat Burst

A heat burst is a sporadic meteorological event that is defined by strong gusts of dry winds accompanied by a sudden and significant rise in temperature. This phenomenon usually occurs during the summer months, typically on warm days during the evening in the wake of a dissipating thunderstorm.

In simple terms, a heat burst is a warm and dry gust of wind that occurs on a hot day during the summer months and usually takes place in the evening. It follows in the wake of a dissipating thunderstorm and causes a significant rise in the surrounding air temperature.  

Its formation is similar to that of a microburst, but as you will soon learn, a few subtle differences create a very different outcome.

How A Heat Burst Develops

When a storm cloud starts to dissipate, lifts, and clears up, it leaves a layer of cold air behind. At this stage, most moisture has been removed from the air during rain showers or other forms of precipitation.

Due to gravity and disappearing updrafts, the dense air starts to sink to the ground. As it accelerates down, it gets subjected to increasing air pressure and friction.

The increased atmospheric pressure causes the air to warm adiabatically (similar to Chinook of Föhn winds down the slopes of a mountain). The friction between falling and stationary particles creates additional heat that contributes to the thermal buildup of the falling air.

Development Of A Heat Burst

The red arrows indicate the dispersing warm & dry winds of a heat burst below remnants of a dissipating storm cloud. Click on the image for a larger view.

The heated air also forces the remaining moisture to evaporate, while momentum allows the layer of air to continue to speed to the ground. The result is a heated, dry pocket of air that hits the surface, forcing warm gusty wind to disperse away from this point of impact.

To those readers familiar with a microburst, this process may sound similar to the formation of a microburst. There are some similarities but also a few different characteristics that allow for the creation of a very different phenomenon.

These are among some of the defining characteristics of a heat burst that will be discussed in the next section.  

Characteristics Of A Heat Burst

For a heat burst to take place, a few conditions need to be in place. Some of them are not only characteristic of the phenomenon but also are what differentiate them from other weather events like microbursts. We look at them first.

1) High Elevation

A heat burst typically originates high in an anvil cloud (that is so synonymous with thunderstorms). It is due to the fact that the phenomenon occurs in the wake of dying thunderstorms, when clouds start to lift and dissipate, leaving a layer of cold air behind.

Anvil Cloud

It is at this high altitude at where a heat burst forms, which allows it to travel further when it sinks to the ground. The greater distance enables it to be subjected to increased pressure and friction for an extended period, causing more heat to build up in the layer of falling air.

The lower altitude (combined with a higher moisture content) at which a microburst occurs is part of the reason that the air reaching the ground remains cold and sometimes mixed with different types of precipitation.

2) Little Or No Moisture 

Another characteristic that is unique to a heat burst compared to similar events is the extremely dry air associated with this phenomenon.

By the time a heat burst starts forming, the storm system already dissipated, and most of the moisture lost due to heavy rainfall that occurred during the peak of the thunderstorm.

The little moisture that is left in the pocket of air evaporates in the warm air as it plummets to the ground. It is not uncommon to observe the phenomenon called virga (visible rain that evaporates before reaching the ground) beneath the cloud base, where a heat burst occurs.

The opposite is true for a microburst. The high moisture content within a thundercloud allows this phenomenon to stay cold or even be cooled further as it descends to the surface.

3) Strong Winds

One of two main characteristics of a heat burst is the strong gusts of winds that it produces as the pocket of warm air hits the ground gets dispersed in multiple directions over the surface of the surface.

The height from which the layer of air falls allows it to accelerate and reach high velocities before hitting the ground. Wind gusts can easily exceed 121 km/h (75 mph). For example, in May 1996, Oklahoma experienced a heat burst with wind gusts of up to 153 km/h (95 mph).

4) Sharp And Significant Temperature Rise

Temperature Rise

The second and most defining main characteristic of a heat burst is the sudden and significant rise in temperature at the surface. This sudden rise in temperature can last anything from a few minutes to a couple of hours.

In most cases, the rise in temperature occurs in a short amount of time. The temperature increase is also significant. It is capable of increasing the current atmospheric warm air by as much as 10° Celsius (50° Fahrenheit) or more.

Extreme examples include Almeria, which occurred in Spain in July 2019. Temperatures jumped from 28° Celsius (82° Fahrenheit) to an incredible 41° Celsius (106° Fahrenheit) in just 30 minutes. 

In July 2016, Oklahoma also experienced a similar heat burst when the temperature rose from 27° Celsius (80° Fahrenheit) to 41° Celsius (106° Fahrenheit).

Conclusion

What became clear throughout this post is that a heat burst may not be such a well-known weather event, but one that will definitely be noticed if ever experienced. It has a dramatic effect over a short period, as the few examples in the last section illustrated. 

It should not be confused with a heatwave, though, which can last for days or months and also have a significant impact on weather and climate of any region it impacts.

This post aimed to illustrate what a heat burst is, how it develops, as well as highlighting the characteristics that define it. If the phenomenon were unknown or unclear to you, you would now be able to understand it, as well as the mechanisms that underlie it, entirely.

Never miss out again when another interesting and helpful article is released and stay updated, while also receiving helpful tips & information by simply  clicking on this link .

Until next time, keep your eye on the weather!

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What Are The Doldrums? The Intertropical Convergence Zone Explained

What Are The Doldrums-The Intertropical Convergence Zone Explained

Many readers may be familiar with the saying, "in the doldrums," referring to a depressed person. But the doldrums actually refer to a specific region with weather conditions feared by ancient mariners.

The doldrums refer to the Intertropical Convergence Zone, a calm, windless region close to the Equator where the northeastern and southeastern trade winds converge and collide. Sailors used the nautical term during the 19th century to describe this part of the ocean with little to no wind activity.

In truth, it dates back as far as the mid 19th century when this nautical term originated with sailors of the time when they used it to describe their predicament when their ships came to a stop and were unable to make any progress for days or even weeks on end.

This article explores what precisely the doldrums are, how it occurs, and look at some of its main characteristics.

Doldrums Definition

During the introduction, you already got a glimpse of what the doldrums are, but the description is vague and needs a more thorough and precise explanation. Before delving into the details, though, it is important to define the term first to lay the foundation:

What Are The Doldrums?

What Are The Doldrums

The doldrums refer to the Intertropical Convergence Zone, a calm, windless region close to the Equator where the northeastern and southeastern trade winds converge and collide. Sailors used the nautical term during the 19th century to describe this part of the ocean with little to no wind activity.

"The doldrums" is an old nautical term used by sailors during the 19th century to describe the part of the ocean where their sailing ships got stuck and were unable to make much progress due to the lack of wind.

It is clear from the definition that the doldrums is a location (the Intertropical Convergence Zone) and not a situation, as the introduction implied. It may sound a bit confusing, but as you will soon learn, this is simply a result of miscommunication during the 19th Century.

Needless to say, there was no radio or any other modern form of direct communication during this period. As a result, communication between ships and their headquarters thousands of miles away had to be relayed via written word or simple "word of mouth."

As a result, when reports reached officials on the mainland, describing the conditions they experienced as being "in the doldrums," it was misinterpreted as the sailors describing an actual location called the doldrums.

Without the misunderstanding corrected, a president was set, and the rest, as they say, is history. Today, the Intertropical Convergence Zone (ITCZ) still commonly gets referred to as the doldrums.

How The Intertropical Convergence Zone Is Formed

As mentioned in the description, the Intertropical Convergence Zone (ITCZ) develops where the northeastern and southeastern trade winds meet at the thermal equator. (The thermal equator is not a fixed position on the planet's surface, but more on that in the next section.)

The ITCZ moves with the thermal equator as it shifts around 5 degrees north and south of the physical equator throughout the year. (For easier reading, the Intertropical Convergence Zone will be referred to as the ITCZ or doldrums for the remainder of this article.)

Formation Of The Intertropical Convergence Zone

The formation of a high-pressure system in the ITCZ. Click on the image for a larger view. 

The sun heats the surface of the land and sea at the thermal equator, causing it to warm the air directly above the surface. As the air warms and expands, it starts to rise, creating an area of low pressure at the surface. (Learn more about low-pressure systems in this article.)

The southern and northeastern trade winds approach each other and converge at the thermal equator. As they encounter the low-pressure system and rising air in the region, these stop moving in a horizontal direction and start to move vertically with the rising air.  

As a result, there is almost no horizontal air movement remaining at the surface, and the little wind present is highly erratic. It is these windless conditions that form the ITCZ, more commonly described as the doldrums by the mariners of the 19th century.  

This band of low-pressure and relatively windless conditions, called the ITCZ or doldrums, encircles the entire planet and follows the thermal equator as it meanders to the north and south throughout the year.

Features Of The Intertropical Convergence Zone

With a clear understanding of how the ITCZ or doldrums develops, it is also beneficial to be aware of the different characteristics that this weather phenomenon display. The most notable of these have already been touched on but needs to be explained in more detail:

  1. Shifting Position
  2. Low-Pressure System
  3. Large Amounts Of Humidity And Rainfall
  4. Very Little And Erratic Air Movement

By looking at each characteristic individually, it will be easier to understand and see how it fits into the larger mechanism that drives the ITCZ.

1) Shifting Position

Throughout the year, the ITCZ moves with the thermal equator as it shifts around 5 degrees north and south of the geographical equator. This movement is closely related to the seasonal movement of the sun.

ITCZ Seasonal Shift

As a result, the ITCZ moves north during the summer months in the Northern Hemisphere and reaches its furthest point during July/August. It then returns south and crosses into the Southern Hemisphere, reaching its most southern position around January/February.

This is a very general description of the movement of the ITCZ. Its actual motion is more complex, and its position can shift unexpectedly over some regions. It can also remain over an area or stay away from it for extended periods with potentially devastating results.

Another variable that influences the movement of the ITCZ is the fact that the ground surface warms up more quickly than the ocean's water when exposed to solar radiation. It results in the ITCZ extending further over land than the sea at the same latitude.

Countries within the Tropics rely on the rainfall that occurs with the arrival of the ITCZ, which means that they can be severely affected by an unnaturally long stay or absence.

During a prolonged absence, a region may experience severe drought, depending on the length of time the ITCZ stays away. When this occurrence remains over an area for an abnormally long period, however, the large amount of rain can lead to widespread flooding.

2) Low-Pressure System

Although this post already briefly mentioned the development of a low-pressure system, it needs a more elaborate explanation to understand its importance.

The planet's surface at the Tropics receives more direct and intense solar radiation from the sun than any other part of the world. As a result, both the ocean and land surface get extensively warmed up.  

In turn, the surface heats the air directly above it. As the air gets warmer, it expands and becomes less dense than the surrounding cold air. This leads to the lighter layer of air starting to rise, which leaves an area of intense low pressure near the ground. 

The importance of this powerful low-pressure system can not be emphasized enough. It is this weather condition that forces the air from the approaching trade winds to be sucked up in the strong vertical lift, which disrupts its horizontal movement.

3) Large Amounts Of Humidity And Rainfall

If you look at a satellite image of the Earth, the ITCZ can easily be identified by the band of clouds encircling the planet near the Equator. It represents the high humidity that forms the numerous rainclouds and thunderstorms occurring in this part of the world.

Heavy Rainfall

The high temperatures at the surface in the Tropics, combined with an abundance of water sources, leads the air to be saturated with moisture. As the moist air starts to rise and gain altitude until it reaches dew point, and condensation takes place.

The resulting stormclouds that form contain a large volume of water droplets. When it can no longer carry them, a burst of intensive and heavy rainfall follows. Although the rain does not last long, a large amount of water gets released in a very short period of time.

It is these short, intense rain showers that are so typical of the weather produced in the Intertropical Convergence Zone.

4) Very Little And Erratic Air Movement

It has been mentioned numerous times throughout this article, but as it is the primary reason for this article and the reason the term doldrums exist, it is worth noting again.

The most well-known characteristic of ITCZ is the absence of wind or very little and erratic air movement. The reason for this phenomenon has already been thoroughly explained.

It is also important to note that even modern sailing boats, no matter how technologically advanced, still battle to make progress and attempt to avoid getting caught in the clutches of this windless region at any cost. 

Conclusion

Even though the saying "in the doldrums" may become a bit outdated, it is still used across the world without knowing the real origin of the term.

By now, there should be no confusion or doubt as to where the term, the doldrums, originated. Whether you want to refer to it as the doldrums or the Intertropical Convergence Zone, the dangerous windless conditions that define them remain ever-present.

Never miss out again when another interesting and helpful article is released and stay updated, while also receiving helpful tips & information by simply  clicking on this link .

Until next time, keep your eye on the weather!

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