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Rainbow Facts: What Is A Rainbow And How Does It Occur?

Rainbow Facts

It is safe to say that the rainbow is probably one of the most photographed and well-known weather phenomena on the planet. But what precisely is a rainbow, and how does it develop?

A rainbow is an optical meteorological phenomenon that occurs when water droplets in the atmosphere refract, reflect, and disperse sunlight into its spectral colors, which appear as a multicolored arc to the observer. It typically occurs when direct sunlight and raindrops are simultaneously present in the sky.

Almost every human on the planet is familiar with the multicolored arc of a rainbow formation spanning across the sky. Even the few readers who never observed one have probably seen several images and illustrations of this meteorological phenomenon.

Although it usually occurs on a rainy day when the sun breaks through the clouds, it can also happen under similar conditions when water droplets in the air come into contact and transform sunlight.

This post examines what a rainbow is, how it is formed and looks at the different types of rainbows. It also highlights the key facts that define this meteorological phenomenon.

Rainbow Definition - What Is A Rainbow?

Before one can start looking at the formation of a rainbow and the key facts that define it, one needs a more elaborate definition of the phenomenon. The introduction already provided a brief description, but a more comprehensive description of a rainbow:

What Is A Rainbow?

What Is A Rainbow

A rainbow is an optical meteorological phenomenon that occurs when water droplets in the atmosphere refract, reflect, and disperse sunlight into its spectral colors, which appear as a multicolored arc to the observer close to the horizon. 

A rainbow typically develops when direct sunlight and raindrops are simultaneously present in the atmosphere on opposite sides of the sky. It is the result of sunlight being reflected by water droplets at an angle of between 40° to 42° to the observer.

The word "rainbow" originated from the Latin word "arcus pluvius", which literally translates to "rainy arch."

A rainbow is a meteorological phenomenon that is, in fact, nothing more than an optical illusion. It is not an actual physical object and also has no physical location. It is simply light being reflected and dispersed that, under the right conditions, reach an observer's location.

It typically appears when raindrops are present in the air and are exposed to (usually) direct sunlight low on the horizon on the opposite side of the sky. This explains why rainbows normally appear in the west in the morning and in the east in the late afternoon.

Rainbow

The multicolored arc one observes is a result of sunlight refracted and reflecting off the back of a water droplet, which also disperses the white sunlight and breaks it up into its seven spectral colors (red, orange, yellow, green, blue, indigo, and violet.)

Red (the color with the longest wavelength) bends at an angle of 42 degrees and appear on the outer edge of the bow, while violet (the color with the shortest wavelength) bends at an angle of 40 degrees and appear on the inner edge of the arc.

All rainbows are technically in the shape of a full circle, but since they occur so close to the ground, one only observes the arc visible above the horizon. The antisolar point, the theoretical center of a rainbow, is almost always positioned at a point below the horizon.

A rainbow and sun always appear on the opposite sides of the sky. As a result, when viewing a rainbow, an observer will always be standing with his/her back to the sun. (Sunlight travels past the onlooker, which gets reflected and dispersed by water droplets back to the viewer.) 

Rainbow Formation: How A Rainbow Develops

With a better understanding of what a rainbow is and the characteristics that define it, one needs to look at how a rainbow is formed to clarify why and how it occurs. The following steps detail the progression in the development of a rainbow:

Rainbow Formation

Illustration demonstrating the path of sunlight through a water droplet to explain the formation of a rainbow. Click on the image for a larger view.

  1. 1
    For a rainbow to develop, both water droplets as well as (direct) sunlight needs to be present in the air.
  2. 2
    With the sun and water droplets situated on opposite sides of the sky, sunlight travels through the atmosphere until encountering and hitting the surface of individual water drops, typically in the form of a rain shower.
  3. 3
    Water has a different density than air. As a result, sunlight is bend (refracted) as it enters a water droplet. 
  4. 4
    Inside the droplet, the light also gets dispersed (broken up) into its spectral colors (red, orange, yellow, green, blue, indigo, and violet), which is responsible for the multicolored band of a rainbow.
  5. 5
    Dispersed light continues to travel through the droplet until it reaches the back of the water drop, where it gets refracted and reflected at an angle of between 40 and 42 degrees from the direction the sunlight entered the water droplet.
  6. 6
    The reflected, dispersed light continues to travel back to the surface where an observer, positioned at the right location to view the incoming rays, view it as the familiar multicolored arc that constitutes a rainbow.
  7. 7
    The size of the water droplet determines the size or radius of a rainbow. This is a result of the water droplet's refractive index (the measurement of how much light is bent as it passes through a medium.)
  8. 8
    Observers view rainbows as an arc because the droplets opposite the sun reflect the light back to the viewer at approximately 42 degrees all around. (Rainbows form an imaginary circle, but one only sees the arc visible above the horizon.)

There are other processes involved in the formation of a rainbow and also more factors influencing its appearance, but these are the key steps involved in the development of this meteorological phenomenon.

Types Of Rainbows

Although the principles defining a rainbow and its formation remain the shape, small variations and additional factors can result in different types of rainbows. The following are some of the most common types of rainbows besides primary rainbows:

Double Rainbow

A typical example of a double rainbow.

  • Full-Circle Rainbow: Although only the arc of the rainbow is usually visible from the planet's surface, it is possible to view a full circular rainbow from an elevated position, for example, from an airplane or high mountain peak.
  • Double Rainbow: A raindrop can have more than one internal reflection. This often leads to a double rainbow with the second bow visible on the outside of the primary bow. Its spectral colors are inverted, with red on the inner & violet on the outer edge.
  • Twinned Rainbow: As a result of different sized raindrops and originating from the same base, the very rare twinned rainbow sometimes occur. Unlike a double rainbow, the spectral colors are in exactly the same order in both rainbows.
  • Reflected Rainbow: When viewed from across a relatively calm body of water, light first encounters & reflects off the water droplets in the atmosphere, but also gets reflected by water's surface before reaching the observer, resulting in a reflected rainbow.
  • Monochrome Rainbow: On rare occasions, rain showers close to the horizon can result in the scattering of green, violet, and other spectral colors with shorter wavelengths. This may lead to the formation of spectacular red (or monochrome) rainbows.
  • Fogbow: A fogbow occurs when sunlight encounters tiny water droplets, usually in the shape of fog. The microdroplets scatter the different spectral colors to such an extent that they basically cancel each other out and display a predominantly white bow. 
  • Supernumerary Rainbow: A supernumerary rainbow occurs when smaller pastel-colored bands appear inside the violet (inside) boundary of the primary rainbow. They are the result of the presence of water droplets smaller than 1 millimeter in size.
  • Higher-Order Rainbows: As already described, multiple reflections of light can take place inside a water droplet, resulting in a double rainbow. But even more reflections can occur, resulting in third & fourth-order rainbows, which are seldom visible, though. 

There are even more variations on the primary type of rainbow, but these are some of the  most commonly observed variations.

Rainbow Facts

Previous sections of this article already addressed the definition and formation of a rainbow. The following list provides the reader with some of the key facts and characteristics that define a rainbow:

  1. 1
    A rainbow is an optical meteorological phenomenon that occurs when water droplets refract, reflect, and disperse sunlight at an angle of 42 degrees to an observer on the ground.
  2. 2
    The multicolored arc is a result of water drops breaking (dispersing) the white sunlight into its spectral colors and reflecting it back to observers on the ground.
  3. 3
    The size of a water droplet determines the radius/size of a rainbow. This is a result of water's refractive index.
  4. 4
    The size of a water droplet also determines the brightness of a rainbow. Water drops larger than 1 millimeter in size produce much brighter and well-defined colors than smaller droplets.
  5. 5
    A rainbow is not an actual physical object and can never be reached.
  6. 6
    All rainbows are technically in the shape of a full circle, but one only observes the arc visible above the horizon since the observer is usually situated on or close to the planet's surface.
  7. 7
    The theoretical center of a rainbow is called the antisolar point. (The position exactly opposite the sun.)
  8. 8
    A rainbow-producing water droplet can have more than one internal reflection, resulting in a double rainbow.
  9. 9
    A rainbow and the sun always appear on the opposite sides of the sky. (The sun is to the back of the observer viewing the rainbow.)
  10. 10
    Several different types of rainbows exist, including double rainbows, supernumerary rainbows, twinned rainbows, and full-circle rainbows. 
  11. 11
    In Norse Mythology, rainbows were seen as a bridge (called the Bifröst) connecting mortal Earth (called Midgard) to the gods (in a location called (Asgard.)
  12. 12
    The dark piece of sky that exists between a primary and secondary rainbow is called Alexander's band.
  13. 13
    The longest-observed rainbow ever occurred in Taiwan on November 30, 2017. It lasted for almost 9 hours (8 hours 58 minutes).

Although this list does not contain all the data available about rainbows, it highlights the key facts and characteristics of this optical phenomenon.

Conclusion

As this article illustrated, although a rainbow can sometimes appear almost magical and supernatural, it is a simple optical, meteorological phenomenon that results from the refraction, reflection, and dispersion of sunlight by water droplets in the atmosphere.

This article described what exactly a rainbow is and how it develops. It also looked at the different types of rainbows, as well as the key facts defining this optical phenomenon.

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

Until next time, keep your eye on the weather!

Wessel

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Facts About The Exosphere: The Outermost Layer Of The Atmosphere

Facts About The Exosphere

The atmosphere consists of five distinct layers, with the exosphere being one of them. But what exactly is the exosphere, and what are its defining characteristics and facts?

The exosphere is the fifth and outermost layer of Earth's atmosphere, situated above the thermosphere at an altitude of 500 - 1 000 km (311 - 620 miles) and extending to 10 000 km (6 200 miles). It is the atmospheric layer where any remaining properties of Earth's atmosphere transition into outer space.

When viewed from the surface or low Earth orbit, our atmosphere seems to be one continuous layer of air. However, it consists of five different layers: The troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

This article focus on the exosphere, the outermost layer of the atmosphere. It not only examines what the exosphere is but also looks at the characteristics or facts that define it.

Exosphere Definition

what is the exosphere

It was already briefly described during the introduction, but in order to examine the exosphere in more detail, a more comprehensive definition is required.

What Is The Exosphere?

What Is The Exosphere

The exosphere is the fifth and outermost layer of Earth's atmosphere. It is situated above the thermosphere at an altitude of 500 - 1 000 km (311 - 620 miles) and extends to 10 000 km (6 200 miles). The exosphere's lower boundary is also known as the exobase.

It is the atmospheric layer where any remaining properties of Earth's atmosphere transition into outer space. It mostly contains light gas molecules like hydrogen and helium, but also carbon dioxide & oxygen lower near the exobase. It is also home to the Hubble Space Telescope.

The name "exosphere" is derived from Ancient Greek, with "ἔξω éxō" meaning "outside," and "σφαῖρα sphaĩra" meaning "sphere." Directly translated "outside sphere" perfectly describes the exosphere since it is the Earth's outermost layer in a spherical shape.

The exosphere is situated just above the thermosphere, with a thin layer of air called the thermopause separating the two layers. It reaches up for thousands of miles and seamlessly merges with the vacuum of space where all Earth's atmospheric characteristics disappear. 

It does not have a fixed lower boundary but starts at an altitude of approximately 500 - 1 000 km(311 - 620 miles), extending up to a height of roughly 10 000 km (6 200 miles). It also has no clear upper boundary.

The lower boundary is also called the exobase. The exobase is also known as the "critical altitude." Above this height, temperatures remain relatively stable, and barometric conditions are no longer relevant.

Compared to the four layers below it, the exosphere contains little to almost no traces of the characteristics that define the Earth's atmosphere. In fact, the "air" so thin that it resembles interplanetary space more than it does the rest of Earth's atmosphere.

(Gas molecules can travel for hundreds of miles without ever coming into contact or colliding with another particle.)

What sets the exosphere really apart, though, is the fact that small particles in the layer do not react the same as in other atmospheric layers where gas molecules mix and collide with each other. 

The few molecules present in the layer basically never collide. Instead, they enter the exosphere and typically follow a ballistic trajectory, which after reaching their apex (maximum altitude), curve back down and reenter the lower atmosphere.

(Some small particles travel too fast, though, and manage to break free from the Earth's gravitational pull and escape into space. As a result, smaller particles are continuously escaping the planet's atmosphere.)  

The small number of gas molecules present in the exosphere is mostly light gases such as hydrogen and helium. Heavier gas molecules like carbon dioxide and oxygen can be found closer to the exobase.

Temperatures can easily exceed 2 000° Celsius (3 632° Fahrenheit) in the exosphere, but there are no particles to transfer the heat, so one will never experience it. In fact, if exposed, one will experience the typically freezing cold temperatures of outer space in the exosphere.

Hubble Space Telescope

As a result of its vastly different characteristics compared to the other atmospheric layers, it should come as no surprise that some scientists don't regard the exosphere as part of the atmosphere at all and see the thermosphere as Earth's uppermost layer.

Due to its altitude and composition, the exosphere is home to a large number of navigational, communication, and weather satellites. Its most famous inhabitant, though, is the Hubble Space Telescope.

Earth is not the only planet in our solar system that has an exosphere. Jupiter, Mars, and Saturn are just two examples of other planets also having exospheres. 

(Even smaller satellites that do not have atmospheres containing a mix of gases, like the moon and three of Jupiter's moons, have what is called a "surface boundary exosphere.")

Facts About The Exosphere

The following list highlights the characteristics and facts of the exosphere in more detail.

  1. 1
    The exosphere is the fifth and outermost layer of Earth's atmosphere.
  2. 2
    It is situated above the thermosphere at an altitude of 500 - 1 000 km (311 - 620 miles) and extends to 10 000 km (6 200 miles).
  3. 3
    It has no clearly defined lower and upper boundary.
  4. 4
    The exosphere is situated just above the thermosphere, with a thin layer of air called the thermopause separating the two layers.
  5. 5
    The lowest part of the exosphere is also known as the exobase.
  6. 6
    In the exosphere, the air is so thin and contain so few particles that it only makes up 0.002% of the total mass of the Earth's atmosphere.
  7. 7
    The relatively few gas molecules present in the layer basically never collide and follow a ballistic trajectory through the exosphere.
  8. 8
    Temperatures can exceed 2 000° Celsius (3 632° Fahrenheit) in the exosphere, but there are no particles to transfer the heat, so one will never experience it.
  9. 9
    The exosphere is home to the Hubble Space Telescope and a large number of communication and weather satellites.
  10. 10
    Light atmospheric gases like hydrogen and helium are the most abundant in this layer, with a few heavier gases like carbon dioxide and oxygen present close to the exobase.
  11. 11
    A number of scientists don't regard the exosphere as one of the atmospheric layers and view the thermosphere as Earth's outermost layer.
  12. 12
    Other planets in our solar system like Jupiter, Saturn, and Mars also have exospheres. 

This is by no means a comprehensive and exhaustive list that contains all the data available about the exosphere but highlights the key facts and characteristics that define this layer.

Conclusion

As this article highlighted, the exosphere still contains small of the gases present in the other four atmospheric layers, but these quickly disappear as altitude increase and the last traces of the atmosphere transition into the vacuum of space.

It is not surprising, then, that many scientists argue that the exosphere cannot be considered part of Earth's atmosphere and that the thermosphere constitutes the atmosphere's upper boundary.

It is technically still part of the atmosphere, though, and contains a small percentage of the gases found closer to the planet's surface. And, yes, it still has an important role to play, as just illustrated. 

If you are interested in the complete structure and make-up of the atmosphere, this article covers all five atmospheric layers and their relation to each other in more detail.

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!

Wessel

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What Is A Sundog – Defining A Parhelion And How It Occurs

What Is A Sundog

Occasionally, one might look towards the horizon during sunset or sunrise, only to see "multiple suns." You are observing an optical phenomenon called a sundog, but what is it, and how does it occur?

A sundog (or parhelion) is a bright optical phenomenon that occurs near the horizon to the left and/or right side of the sun at a radius of 22 degrees. It is caused by sunlight being refracted by hexagon-shaped ice crystals in Cirrus clouds with their primary axis vertically orientated.

A sundog (or sun dog) is part of a family of optical meteorological phenomena that occurs as a result of sunlight or moonlight being refracted (bent) by ice crystals in high-altitude Cirrus clouds that observers view as different shapes and displays.

The spectacular and more familiar solar halo (or ring around the sun) is the same phenomenon, as well as sun pillars, which also occur close to the horizon. They appear differently, though, partly due to the orientation of the ice crystals and the sun's position.

In this article, we examine what a sundog is and how it is created. We also look at its characteristics and highlight the important facts about this phenomenon.

Sundog Definition

During the introduction, a brief description of what a sundog is was already provided. In order to best understand its characteristics and formation, though, one first needs to establish a more detailed definition:

Sundog Definition

What Is A Sundog

A sundog (also known as a parhelion or mock sun) is a bright optical phenomenon that occurs near the horizon to the left and/or right side of the sun at a radius of 22 degrees. 

It is caused by sunlight being refracted by six-sided (hexagon-shaped) ice crystals in high-altitude Cirrus clouds with their primary axis vertically orientated.

A sundog (sun dog) is officially known as a parhelion, but is also referred to as a mock sun.

The word "parhelion" is derived from the Greek "para-" (meaning beside) and "-hēlios" (referring to the sun). Literally translated, it means "beside the sun," which is exactly where sundogs are situated.

The name "sun dog" also originated in Greek Mythology, where it was believed that Zeus walked his dogs across the sky. Consequently, sundogs represent the dogs of Zeus.

As already mentioned, a sundog is the result of light being refracted through hexagonal ice crystals in Cirrus clouds. But it is not only the hexagonal shape of the crystals that allows for the formation of this phenomenon.

Sundog

The crystals also have a flat, plate-shaped form, which allows it to float horizontally in the air and create the appearance of a sundog on one or both sides of the sun. (As opposed to a solar halo where the ice crystals are more randomly orientated.)

Consequently, these horizontally orientated crystals cause the sunlight to bend through a 22° angle towards the observer and also break it up into its primary colors.

As a result, the inside edge of a sundog has a red-colored tint, while the rest of the colors blend together to reform the bright white color of the sun. Sometimes, though, a faint blue color forms on its outer edge, or the phenomenon display the full array of rainbow colors.

A sundog is not visible to everyone where the sun shines through Cirrus clouds. It depends on your physical location in relation to the position of the sun. Depending on your position, the ice crystals refract the light from the sun at just the right angle to see the occurrence. 

What Causes Sundog

As mentioned in the previous section, the rings you see around the sun result from the ice crystals in cirrus clouds refracting and reflecting the light in such a way that you can see a ring appearing from your location on the planet's surface. 

what causes a sundog

Illustration describing the formation of a sundog. Click on the image for a larger, more detailed view.

A few things need to be in place in order, though, to observe sundogs beside the sun clearly.

  1. 1
    The sun needs to be close to the horizon in a mostly clear sky.
  2. 2
    Secondly, a relatively clear sky with only a thin layer of cirrus clouds high up in the atmosphere is essential. (Due to the Earth's natural curvature, it will appear to be hovering over the horizon.)
  3. 3
    As sunlight reaches the cirrus clouds close to the horizon (from the observer's perspective), it gets refracted and "bend" by the ice crystals.
  4. 4
    The refraction by the ice crystals causes the light to be projected in a different direction. 
  5. 5
    If the light is refracted or "bend" at a  22-degree angle, the sundog will become visible to the observer. (This also means the sundog is situated at a radius of about 22 degrees to the side of the sun.) 

As mentioned, a sundog is not always visible to anyone viewing the sun through a layer of cirrus clouds near the horizon. One has to be in the right location on the planet in relation to the sun's location, with plate-shaped ice crystals in the clouds also orientated correctly.

Facts And Characteristics Defining A Sundog

The following list summarizes and highlights some of the key facts and characteristics regarding a sundog, some of which have already been explained in more detail elsewhere in this article:

  1. 1
    A sundog is an optical meteorological phenomenon that occurs near the horizon to the left and/or right side of the sun.
  2. 2
    It is the result of plate-shaped hexagonal icy crystals in high-altitude cirrus clouds refracting sunlight towards the observer.
  3. 3
    A sundog (sun dog) is officially referred to as a parhelion but is also known as a mock sun.
  4. 4
    It is the same type of meteorological phenomenon as a solar halo and it's not uncommon for the two to appear together at a radius of 22 degrees from the sun.
  5. 5
    It has a predominantly bright white color, but since ice crystals break up the sunlight into its primary colors, sundogs usually have a red tint on its inner boundary (facing the sun).
  6. 6
    As a result of ice crystals breaking up sunlight into its primary colors (like a prism), a sundog occasionally displays the full range of colors similar to a rainbow.
  7. 7
    A sundog is a phenomenon that also occurs on other planets in our solar system like Saturn, Neptune, and Jupiter.
  8. 8
    Sundogs are named after the "dogs of Zeus in Greek" Mythology.

This is by no means an exhaustive and complete list but focused on the key aspects that define a sundog (or parhelion).

Conclusion

As this article clearly highlighted, the "mock sun" appearing on one or both sides of the sun is not an abnormal or inexplicable event.

It has a logical and scientific explanation for its occurrence, which has everything to do with what is going on in our own atmosphere, and nothing with what is happening in space around the sun itself.

It is also worth mentioning again that the ring one sometimes observes around the sun (solar halo) is also exactly the same type of phenomenon as a sundog.

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!

Wessel

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What Causes Humidity? Defining Humidity And Its Characteristics

What Is Humidity heading

For meteorologists & weather enthusiasts, the importance and impact of humidity on various weather events and atmospheric conditions are well-known. But what precisely is humidity, and what causes it?

Humidity refers to the amount of water vapor (water in its gaseous state) present in the air at a given time. High humidity levels are typically associated with precipitation. It can be felt but is normally invisible. It is usually represented as relative humidity (as opposed to absolute humidity).

At any given time, no matter where we find ourselves (indoors or outdoors), we are constantly surrounded by air containing a certain percentage of humidity.

Humidity

There is no dispute about the vital role water play in meteorological activities. After all, it is the primary driving force of almost any weather occurrence.

But humidity plays an even more essential role in the transport of water between different regions. This clearly illustrated when one looks at The Water Cycle.

It is also crucial for air to contain just the right amount of moisture to maintain a "balanced" air ratio to benefit the environment and all living organisms. (Too little or too much humidity and it can negatively impact the environment and even human health.)

In the following sections, we take a closer look at how humidity it is caused, how it is measured, and its impact on weather events.

What Causes Humidity?

With humidity clearly defined, one needs to take a close look at how it is caused in the first place and examine its formation: 

Humidity is caused when water turns from its liquid or solid state into its gaseous form (water vapor). This occurs due to evaporation & transpiration (evapotranspiration), which typically occurs as a result of heating through solar radiation, but also through friction as precipitation travels through air particles.

As radiation from the sun heats the planet's surface, water evaporates from bodies of water (oceans, lakes, dams, puddles) and also from surfaces that are rich in water content like soil. The evaporation process turns water into its gaseous state.

Vegetation

Vegetation in the form of trees and plants also release water into the atmosphere through their leaves in a process called transpiration. (The combined processes of evaporation and transpiration is called evapotranspiration.)

The evaporation of water is not only the result of solar radiation, though. When precipitation takes place, waterdrops, hail, or snow starts falling towards the ground and accelerate. 

As it gains speed, the water starts experiencing drag due to friction with particles and molecules in the air. The friction creates heat, resulting in a significant amount of evaporation to take place, turning some of the precipitation into water vapor, 

All these processes are responsible for increasing the humidity in the air.

Facts About Humidity

In earlier sections, the definition and cause of humidity were already established. The following list, though, highlights the key facts and characteristics surrounding this element of weather:

  1. 1
    Humidity refers to the amount of water vapor present in the atmosphere at any given time.
  2. 2
    Water vapor is nothing more than water in its gaseous state.
  3. 3
    Humidity is caused when water is turned from its liquid or solid into its gaseous state.
  4. 4
    Although humidity and its effects can usually be felt, it is normally invisible to the naked eye.
  5. 5
    Meteorologists use dew point to measure the amount of water vapor present in a body of air.
  6. 6
    Humidity is a crucial element necessary for the formation of snowflakes and hailstones in subzero temperatures, which you can read more about in this article.
  7. 7
    Air contains a certain percentage of humidity at all times.
  8. 8
    Relative humidity is a more accurate reflection of humidity than absolute humidity.

This is a concise and cryptic list of the most important characteristics and facts that define humidity, but the details about specific aspects are highlighted in other sections throughout this report.

Relative Humidity Vs Absolute Humidity

Before explaining how humidity is measured, we need to address the difference between relative humidity and absolute humidity, as there is some confusion about the difference between the two.

Absolute humidity is the measurement of the amount of water vapor in the air. It is a very rigid form as measurement, as it does not take variables like temperature into consideration. It is normally indicated as grams of moisture per cubic meter of air (g/m3).

Relative Humidity

Relative humidity is also the measurement of the amount of water vapor in the air. Unlike absolute humidity though, it is measured relative to the temperature of the air.

In other words, relative humidity measures the percentage of water vapor present in the air relative to the maximum amount of vapor that can be held at a given temperature.

This is important, as warm air can hold much more water vapor than cold air.

If absolute humidity is used to measure the water vapor in both warm and cold air, and it measures identical water vapor percentages in both, it is misleading and not representative of the actual atmospheric conditions.

(In this case, the relative humidity in the cold air is much higher than that of the warm air since warm air holds more moisture than cold air. To get an equal absolute humidity reading, more water vapor must be present in cold air to match the warm air's moisture.)

For this reason, relative humidity is the best and most widely used way of measuring moisture levels as it most accurately reflects the actual atmospheric conditions.   

How Humidity Is Measured

The instrument used to measure the humidity in the air is called a hygrometer. There are a variety of these instruments that have been used throughout the years.

The psychrometer is probably the most well-known early example of a humidity measuring device. It basically consists of two thermometers (one being covered with a wet cloth) used to measure the humidity.

The bulb of the thermometer covered by the wet cloth measures a lower temperature as a result of the evaporation of the moisture in the cloth. By using the difference between the two different temperature readings, the humidity is measured.

Obviously, this is not a very accurate and reliable way of measuring humidity.

hygrometer

A capacitive or resistance hygrometer uses a much more reliable way to measure humidity. A material able to absorb moisture is used. The amount of moisture influence the material's ability to carry an electrical current. 

An electrical current is then sent through the material and measured. Based on the strength of the current (influenced by the amount of moisture absorbed by the material), the amount of humidity in the air can be measured.

The process clearly is a bit more complex than just explained. To get a better understanding of hygrometers and how they measure humidity, you can read more about it in this article.

The Effect Of Humidity On The Weather

Humidity is one of the main driving forces of almost weather systems around the world. Actually, the combination of humidity and temperature are the impetus of many weather systems and occurrences.

The moist air in a warm front gently moves over a cold front and cools down as it rises. It results in condensation and cloud formation, which leads to the gentle precipitation that is welcoming to the agricultural sector. (Similar to the weather produced by a stationary front.)

On the other side of the scale, the warm moist air over the oceans of the tropics rises and forms powerful low-pressure systems. As the air keeps rising and rotating winds are pulled in and building up around the low-pressure center, the warm, humid air keeps feeding the growing system.

hurricane, cyclone and typhoon

What was a tropical depression can now quickly build into a tropical storm. If enough humid air builds up in this system and stays over the warm ocean waters long enough, hurricanes of varying strength can be very destructive when it makes landfall.

And this whole process got started by some humid air rising up from the ocean's surface. That is why these warm tropical waters are called the engine rooms of big storm systems and the fuel that drives these massive systems.

Similarly, the torrential rains falling during the Monsoon Season over India and Southeast Asia are all part of the circulation pattern that brings huge amounts of humid air from the warm Indian and Western Pacific Oceans during the warm summer season.

As is the case with hurricanes and tropical storms, moisture-filled air is once again one of the main driving forces of a major weather system. This is also another example of how humidity and temperature work together in the creation of a major storm system.

There are obviously many more processes involved in the formation of all these weather systems. If you want to read in detail how hurricanes and monsoons are formed, as well as the role humidity plays in all this, you can read the in-depth article here.

Conclusion

The meaning of humidity, in other words, what exactly it is, should now be very clear. You also now know how it is formed. It may not always be always visible, but its power and influence can never be underestimated.

The powerful effect it has on the weather on a global scale should also be very evident, and we have just touched the surface.

There is actually so much more to humidity than I covered in this post, but as long as you now have a clear understanding of what exactly humidity is and how it is formed, this article served its purpose.

Feel free to leave me any comments, questions or suggestions, and I will get back to you as soon as possible.

Remember to join my  Mailing List  to be informed whenever a new article is released, and share new developments and helpful hints & tips.

Until next time, keep your eye on the weather!

Wessel

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Solar Halos: Defining The Rings Around The Sun

Solar Halos

Occasionally you might look up at the sky and notice a hazy rainbow-colored ring around the sun. This spectacular phenomenon is called a solar halo (or 22-degree halo), but what are they & how does it occur?

Solar halos (or 22-degree halos) are hazy rainbow-colored rings that occur at a radius of approximately 22 degrees around the sun. It is the result of the sun's light being refracted by ice crystals in Cirrus clouds in the upper troposphere at an altitude of approximately 6000 meters (20 000 feet).

These multi-colored optical phenomena can occur quite frequently and are not an unfamiliar sight, yet very few people really know what exactly these rings around the sun are or how they are formed. 

This article examines what these rings (or solar halos) are and how they are created. It also looks at its characteristics and the conditions surrounding it.

Solar Halo Meaning

The introduction already provided a brief description of what this spectacular-looking meteorological phenomenon around the sun is. To better understand its formation, though, one first needs a more elaborate and detailed definition.

Solar Halo Meaning

Solar Halo Meaning

Rings (or halos) around the sun are the refraction of the sunlight by millions of ice crystals present in cirrus clouds drifting at a height of 6000 meters (20 000 feet) or more above the earth's surface. 

The hazy rings appear at a radius of approximately 22 degrees around the sun, which are characterized by various degrees of predominantly rainbow colors and an undefined, fuzzy border.

It occurs in the upper troposphere, where temperatures are too low for water droplets to remain in its liquid form. The hexagon shape of the ice crystals breaks the sunlight up and refracts back to Earth.

A solar halo goes by many different names. Sometimes it is simply referred to as "the ring around the sun." The scientific community refers to it as a 22° halo, but it is also known as a halo, sun halo, 46° halo, or rainbow halo.

The color of a solar halo varies from a faint rainbow color to a pale white tint. The rainbow colors are the result of the ice crystals breaking up the white light into its primary colors. Sometimes, though, the primary colors combine and blend together to form a white tint.

(The hue and intensity of the color largely depend on the strength of the sunlight, density of the clouds, and the angle of refraction.)

The halo is not visible to everyone where the sun shines through Cirrus clouds. It depends on your physical location in relation to the position of the sun. Depending on your position, the ice crystals refract the light from the sun at just the right angle to see the occurrence. 

A solar halo is exactly the same phenomenon that occurs during the daytime around another celestial body. The halo you see around the moon is the same meteorological phenomenon. Instead of sunlight, though, it is the moonlight that is refracted in this case.

What Causes The Ring Around The Sun

As mentioned in the previous section, the rings you see around the sun result from the ice crystals in cirrus clouds refracting and reflecting the light in such a way that you can see a ring appearing from your location on the planet's surface. 

A few things need to be in place in order, though, to observe these rings surrounding the sun clearly.

  1. 1
    The presence of the sun in a mostly clear sky.
  2. 2
    Secondly, a clear sky with only a thin layer of cirrus clouds high up in the atmosphere is essential. (Thicker clouds present lower down in the atmosphere will obscure or eliminate the effect.)
  3. 3
    As the light from the sun hits the cirrus cloud, it gets refracted and "bend" by the ice crystals. The refraction by the ice crystals causes the light to be projected in a different direction. 
  4. 4
    If the light is refracted or "bend" at a certain angle, specifically 22 degrees, the rings will become visible to the observer. (This also means the rings have a radius of about 22 degrees around the sun.) That is why this occurrence is also referred to as 22-degree halos by scientists and meteorologists. 

As already mentioned, an individual also has to be in the right geographical location on the planet's surface )in relation to the sun's location) to observe this phenomenon.

Characteristics Of The Rings Around The Sun

A notable feature of the halo surrounding the sun is the lack of a clear and well-defined border. The fuzzy border is the result of millions of ice crystals refracting the light in multiple directions that it makes it impossible to create a clear and well-defined border.

The ring around the sun has a mostly rainbow-colored hue but can also display a pale white color as a result of primary colors blending together and canceling each other out. This a direct result of the hexagon shape of the ice crystals.

ring around the sun

Like the shape of raindrops causing the different colors in a rainbow to appear, the faceted (hexagon) shape of ice crystals refracts the light of the sun and breaks it up into its primary colors.

This is why you will occasionally notice some rings around the sun to have a red tint on the inside and a blue tint on the outside. 

As the sun is much brighter than the moon, the rings around the sun not only display rainbow-colored hue but also appear much brighter and clearly defined due to the increased luminescence.

What is also very noticeable is the fact that the sky between the edge of the sun and the halo always appears darker than the rest of the sky.

On rare occasions, one may also catch a very rare glimpse of not one but a double halo surrounding the sun. 

Halo Around The Sun Superstition

Over centuries, many cultures worldwide believed a ring around the sun is a sign that rainy weather is on the way. This is neither a myth nor a superstition. The presence of high cirrus clouds is very often an indication of wet and stormy weather on the way.

Cirrus clouds normally precede low-pressure systems by a day or two, and as many of you may already know, low-pressure systems are normally at the heart of stormy wet weather. (You can read more about low-pressure systems and cold fronts in this article.)

During biblical times, the rainbow was used as a sign from God as evidence of His covenant with Noah never to flood the Earth again. The rainbow-colored halo around the sun has the name significance as the traditional rainbow.

In African mythology, a solar halo is seen as a sign of great change ahead. (They also believe that it signals the arrival of rain, which is more in line with scientific evidence.)

Conclusion

As this article clearly illustrated, the multicolored ring around the sun that sometimes occur under ideal conditions is not nearly as mysterious or uncommon as one might think.

There is a very logical and scientific explanation for its occurrence, which has everything to do with what is going on in our atmosphere, and nothing to do with what is happening in space around the sun itself.

It is also worth mentioning again that the halo one sometimes observes around the moon is also exactly the phenomenon that occurs around the sun.

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!

Wessel

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Facts About The Aurora Borealis: What The Northern Lights Are And How They Occur

Facts About The Aurora Borealis

It is a fair assumption to make that the majority of us never observed the Polar or Northern Lights in person, yet we are all familiar with images of this spectacular phenomenon. But what exactly is the Aurora Borealis?

The Aurora Borealis (also known as Northern Lights) is an optical meteorological phenomenon that occurs in the upper atmosphere above the Arctic Circle. It appears as bands of colored lights, resulting from charged particles in solar winds that collide and react with gases in the thermosphere.

It is probably one of nature's most breathtaking displays, but due to their location, few of us ever get to see an Aurora Borealis occurrence. Situated over the Arctic and Antarctic regions, this phenomenon has also been the source of some of awe-inspiring photographs.

This article examines what this multicolored light display is and also how it occurs. It also looks at the facts and characteristics that define it.

Aurora Borealis Definition

Several different factors are involved in the creation of the Aurora Borealis, which interactions with each other result in the occurrence of this optical phenomenon. Before examining it in more detail, one needs to obtain a more elaborate definition of this event.

The introduction already provided a brief description of what the Aurora Borealis is, but one needs a more detailed and concise explanation of this occurrence before continuing.    

What Is The Aurora Borealis?

What Is The Aurora Borealis

The Aurora Borealis (or Northern Lights) is a meteorological phenomenon that occurs over the Arctic Circle at a height of approximately 90 - 150 km (56 - 93 miles) above the planet's surface. It appears as bands or curtains of multicolored lights (predominantly green, violet, and pink).

It is the results of charged particles in solar winds that collide with gas molecules in the upper atmosphere (specifically the thermosphere and exosphere). The resulting ionization of particles is what causes the visual light display over polar regions.

The name, Aurora Borealis, is derived from the names of gods in Roman Mythology. "Aurora" was the Roman goddess of dawn, while "Borealis" is the god of the north wind. The term was coined by Galileo Galilei, an Italian astronomer, in 1619.

In Norse Mythology, the Aurora Borealis was believed to be a bridge made of fire that extended into the sky.

This meteorological phenomenon also goes by several names, including the Northern Lights, Polar Lights, Merry Dancers, and Aurora Polaris. It also has different names when it occurs in the Southern Hemisphere over Antarctica, but more on that later.

The primary colors that are displayed are luminous green, violet, and pink. It also produces hues of blue, yellow, and occasionally white and orange.

When particles collide with nitrogen, the result typically produces deep red and violet colors. When a collision between charged particles and oxygen occurs, though, it produces the colors green and yellow. 

aurora borealis

The Aurora Borealis occurs in the magnetosphere, the magnetic field that surrounds and protects the Earth from incoming solar winds. It starts several hundred kilometers above the Earth's surface but extends further than 600,000 kilometers (370,000 miles) in altitude.

(It should not be confused with Earth's 5 atmospheric layers, though, which are categorized according to air density, temperature, meteorological activity, and gravitational force. Technically, the magnetosphere starts in the thermosphere and extends into outer space.)

Types Of Aurora Borealis

Auroras literally come in all shapes and sizes. According to astronomer, to Dr Stuart Clark, the Aurora Borealis can be divided into 5 categories. The following list name them in order from dimmest to brightest: 

  1. Diffused light appearing close to the horizon that may be hard to observe.
  2. Bands of light that are similar to arcs, but with more of a curvature.
  3. Arcs appear that extend across the sky.
  4. Rays are curtain-like light and dark stripes, extending into the sky.
  5. Coronas cover vast portions of the sky and extend from horizon to horizon.

There are, off-course, many other types and variations of this phenomenon, but at the core level, they can be broken down into these 5 types of Aurora Borealis.

How The Aurora Borealis Is Formed

The following steps will serve to illustrate how exactly the Aurora Borealis form and develop:

  1. 1
    The Aurora Borealis starts more than 148 million kilometers (92 million miles) away in the center of our solar system, where the Sun produces a wave of charged particles called solar winds that travel to the Earth.
  2. 2
    Solar winds are a result of sunspots that occur when magnetic fields on the Sun's surface collide and explode, sending charged particles in the form of solar winds into the solar system.
  3. 3
    As the solar winds reach the outer limits of Earth's atmosphere, it comes into contact with gas molecules in the upper atmosphere.
  4. 4
    Charged particles from the solar winds collide and interact with the gas molecules, transforming them into a higher state of energy.
  5. 5
    When the atoms in the gas molecules get energized, the electrons in the atoms moves further away from their nucleus. 
  6. 6
    When they return to their rested state, the electrons emit light particles called photons that result in the light display we view as the Aurora Borealis.
  7. 7
    When a nitrogen molecule is energized, it produces colors with a deep red and violet hue. When an oxygen molecule is energized, it produces the colors green and yellow.  

There are other and more detailed processes involved as well, but these steps captured the essence of how the Aurora Borealis forms.

Where Does The Aurora Borealis Occur?

Although we are very familiar with and the vast majority of attention is given to the Aurora Borealis (or Northern Lights), this meteorological phenomenon actually occurs over the polar regions of both the Northern and Southern Hemisphere.

Northern Lights

If it occurs in the Southern Hemisphere over Antarctica and surrounding regions, it is known as Aurora Australis or Southern Lights.

In both hemispheres Auroras are approximately 3 to 6 degrees in width. They are located at between 10° and 20° from the geomagnetic poles.

In the Northern Hemisphere, they can be seen in the Arctic Circle and northern countries bordering it. In the Southern Hemisphere, it can be observed over Antarctica, the southernmost part of Argentina, Australia, and New Zealand. 

Facts About The Aurora Borealis

  1. 1
    The Aurora Borealis is a result of charged particles in solar winds colliding with gases in the upper atmosphere.
  2. 2
    The ionization of gas molecules results in the multicolored display over regions in the Arctic Circle.
  3. 3
    The primary colors of the Aurora Borealis are luminous green, violet, and pink.
  4. 4
    There are 5 types of aurora borealis, categorized according to size and brightness.
  5. 5
    The Aurora Borealis occurs in the magnetosphere, Earth's magnetic field that protects the planet from solar winds.
  6. 6
    According to Norse Mythology, the Aurora Borealis was believed to be a bridge of fire that reached into the sky.
  7. 7
    It appears at an altitude of 90 - 150 km (56 - 93 miles).
  8. 8
    It can extend to over 1000 km (621 miles) above the Earth's surface. 
  9. 9
    The meteorological phenomenon occurs over both poles in the Southern and Northern Hemisphere. It is called the Aurora Australis (or Southern Lights) when it forms over Antarctica.
  10. 10
    It occurs between 10° and 20° from the geomagnetic poles.
  11. 11
    Some observers claim there are sounds associated with the Aurora Borealis, although this claim has not been scientifically proven yet.
  12. 12
    It is clearly visible from space. Some of the most interesting images, putting its size and scale in perspective, have been taken from the International Space Station (ISS). 
  13. 13
    It occurs on other planets, including Jupiter, Saturn, Neptune, and Uranus.

This is not a complete and exhaustive list but highlights the most important and relevant facts about the Aurora Borealis.

Conclusion

As this article clearly illustrated, the Aurora Borealis is a meteorological phenomenon that occurs on a gigantic scale (literally extending hundreds of miles into the edge of space), producing truly breathtaking lighting displays.

But as also explained, it is a natural phenomenon with a clear scientific explanation that has been widely researched throughout the last few centuries. And today, we understand even more about the Aurora Borealis than ever before.

It may not be the "fire bridge to the sky" as the North Germanic people believed, but that does not take anything away from the feelings of awe and magic this spectacular phenomenon evokes.

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!

Wessel

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Facts About The Thermosphere: What It Is, And It’s Defining Characteristics

Facts About The Thermosphere

It may be one of Earth's outermost atmospheric layers, but the importance of the thermosphere should not be underestimated. But what exactly is the thermosphere, and what are its characteristics?

The thermosphere is one of the 5 layers of the atmosphere, situated above the mesosphere and below the exosphere at an altitude of 90 km (56 miles) to approximately 1000 km (621 miles). It is the hottest atmospheric layer and the part of the atmosphere where the Aurora Borealis (Northern Lights) occur.

Situated close to the boundary between the atmosphere and space, the thermosphere is only separated from outer space by the exosphere, Earth's fifth, and outermost layer.

Although Earth's fourth atmospheric layer has very few characteristics in common with the three layers closer to the planet's surface, it still has a valuable role to play.

We examine not only what the defining characteristics of the thermosphere are but also the facts that separate it from the other four layers of the atmosphere.

Thermosphere Definition

Diagram Of The Thermosphere

The thermosphere is the last atmospheric layer which characteristics carry any resemblance to the rest of the atmosphere as we know it. Above its upper boundary, the exosphere blends seamlessly into the vacuum of space.

It was already briefly described during the introduction, but in order to examine the thermosphere in more detail, a more comprehensive definition is required.

What Is The Thermosphere?

What Is The Thermosphere

The thermosphere is the third layer of the atmosphere, situated above the mesosphere and below the exosphere at an altitude of 90 km (56 miles) to 1000 km (621 miles).

The meteorological phenomenon, the Aurora Borealis (Northern Lights), occurs in this layer at heights of 150 km (93 miles) and above.

It is also considered the atmosphere's hottest layer, with temperatures reaching 2000° Celsius (3632° Fahrenheit).

The thermosphere is situated just above the mesosphere, with a thin layer of air called the mesopause separating the two layers. It reaches up to the exosphere, with another thin layer of air called the thermopause separating them.

The name of the thermosphere is derived from the Greek word, θερμός (thermos), meaning heat. (Referring to the high temperatures reached in the layer.)

At 513 km (319 miles), it is the thickest of the atmosphere's four inner layers and thicker than the troposphere, stratosphere, and mesosphere combined. (But not as thick as the exosphere that stretches for thousands of miles into space.)

International Space Station

By some definitions, space starts at 100 km (62 miles) above Earth, so it is not surprising that the thermosphere is seen as part of outer space in many circles. The air is extremely thin at this altitude, where the Earth's gravitational pull is also greatly reduced. 

Due to these characteristics, this is a highly utilized part of the atmosphere where over 800 active satellites orbit the planet, and it is also home to the International Space Station (ISS). 

(Not to mention the large number of space debris also orbiting in the thermosphere.)  

One of the most well-known characteristics of the thermosphere is the presence of the Aurora Borealis (Northern Lights), the spectacular meteorological phenomenon that occurs over regions in the Arctic Circle.

Aurora Borealis

The Aurora Borealis is a result of charged particles from the sun colliding with gaseous particles in the thermosphere. This causes the colorful light display observers in the Northern Hemisphere are so familiar with. (Green is one of the common colors created.)

Another unique feature of the thermosphere is the extremely high temperatures that occur within this layer. With temperatures reaching up to 2 500° Celsius (4 530° Fahrenheit), the thermosphere is the hottest of all the atmosphere's layers by a huge margin.

The temperature is not constant, though. Between day and night, an average difference of 200° Celsius (360° Fahrenheit) can occur. The amount of solar radiation also has a direct influence on the temperature, causing as much as a 500° Celsius (900° Fahrenheit) variation.

You will also not be able to feel the extremely high temperatures this layer experience. The air is so thin that it basically resembles a vacuum,  with no particles/atoms in the air to conduct the heat.

The stratosphere is well-known for containing the important ozone layer, which is essential for protecting life on Earth from the Sun's deadly UV radiation. The thermosphere, though, also plays a role in protecting the planet from solar radiation.  

It absorbs a large amount of incoming Ultraviolet and X-ray radiation, which emphasizes the importance of this layer. The incoming solar rays interact with gas molecules during the absorption process, which contributes to the high temperatures reached within this layer.

A large portion of the Ionosphere also falls within the thermosphere since ions are created when Ultraviolet Radiation causes the photoionization of molecules.

Facts About The Thermosphere

The following list highlights the characteristics and facts of the thermosphere in more detail.

  1. 1
    The thermosphere is the fourth layer of the atmosphere (above the troposphere, stratosphere, and mesosphere.)
  2. 2
    It extends from a height of approximately 90 km (56 miles) to 1000 km (621 miles) above the Earth's surface.
  3. 3
    It borders the mesosphere below through a thin transitional space called the mesopause.
  4. 4
    It borders the exosphere above through a thin transitional space called the thermopause.
  5. 5
    It is the part of the atmosphere where low-orbiting satellites and the International Space Station are found.
  6. 6
    The thermosphere is the hottest of the five atmospheric layers, with temperatures reaching up to  2 500° Celsius (4 530° Fahrenheit).
  7. 7
    It is home to the meteorological phenomenon, the Aurora Borealis (also known as the Northern Lights).
  8. 8
    A large part of the Ionosphere is located in the thermosphere.
  9. 9
    Like the stratosphere, the thermosphere plays an important part in protecting the planet from the Sun's dangerous UV and X-ray radiation through absorption.
  10. 10
    It is the thickest of the four inner atmospheric layers at 513 km (319 miles)
  11. 11
    The layer is characterized by the presence of atmospheric waves (similar to those experienced in our oceans.)
  12. 12
    It makes long-distance radio communication possible by allowing radio waves to bounce off the ions in the layer allowing it to travel over longer distances.

Although this list does not contain all the data available about the thermosphere, it highlights the key facts and characteristics of this layer.

Conclusion

Like the three atmospheric layers below it, the thermosphere has a vital role to play in protecting the planet and all life in it, as this article illustrated.

Although it only has a fraction of the gas and other particles present in lower layers, the thermosphere is situated at the ideal height for low-obit space utilization and contains enough gas molecules to absorb a significant amount of dangerous solar radiation.

If you are interested in the complete structure and make-up of the atmosphere, this article covers all five atmospheric layers and their relation to each other in more detail.

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

Until next time, keep your eye on the weather!

Wessel

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Facts About The Stratosphere: What It Is And Its Defining Characteristics

Facts About The Stratosphere

The atmosphere consists of five distinct layers, with the stratosphere being one of them. But what exactly is the stratosphere, and what are its defining characteristics and facts?

The stratosphere is one of the 5 layers of the atmosphere, situated above the troposphere and below the mesosphere at an altitude of 10 km (6 miles) to 50 km (30 miles). It is the only atmospheric layer where temperature inversion occurs and part of the atmosphere where the ozone layer is situated.

It is easy & understandable to view our atmosphere as a continuous layer of air. However, it is made up out of five different layers: The troposphere, stratosphere, mesosphere, thermosphere, and exosphere. This article focus on the stratosphere, Earth's second layer. 

It not only examines what the stratosphere is but also looks at the characteristics or facts that define it.

Stratosphere Definition

Stratosphere

The stratosphere is situated just above the troposphere, with a thin layer of air called the tropopause separating the two layers. It reaches up to the mesosphere, with another thin layer of air called the stratopause separating them.

Like the other atmospheric layers, it does not have a fixed height but starts at an altitude of approximately 10 km (6 miles), extending up to a height of roughly 50 km (30 miles). It is also roughly 35 kilometers (22 miles) thick.

It is the only atmospheric layer where temperature inversion takes place. It means temperatures rise as altitude increases in this region, unlike the other four layers, which are characterized by a drop in temperature as altitude increases.

Close to the tropopause, temperatures start at approximately -51° Celsius (-60° Fahrenheit) and continue to rise until reaching the stratopause, where temperatures reach -15° Celsius (5° Fahrenheit).

The stratospheric air is extremely thin and dry since the vast majority of atmospheric gases (and weather activity) are limited to the troposphere. This is due to gravity, but mostly due to the temperature inversion in the tropopause that prevents gases from entering the layer.

As a result, the air in the stratosphere is about 1000 times thinner in the stratosphere than at sea level in the troposphere.

aircraft

However, this feature allows commercial airliners to fly in the lower stratosphere while traveling faster and save fuel. The lack of particles in the air causes less friction to hold an aircraft back, which requires less power to travel faster and further.

(The lack of weather activity in the stratosphere also allows aircraft to avoid adverse weather conditions by flying in the lower stratosphere above the weather.)

Since almost weather activity is limited to the troposphere and almost no water vapor is present in the stratosphere, Polar Stratospheric Clouds is the only visual meteorological phenomenon that can be observed in the stratosphere. 

nacreous clouds

Also known as Nacreous Clouds, these unique clouds develop near the poles at an altitude of 15 - 25 kilometers (9 - 15 miles) during the winter months. They are a combination of supercooled water and nitric acid that develop at very low temperatures.\

(Learn more about Nacreous or Polar Stratospheric Clouds in this article.) 

The stratosphere is home to the ozone layer, which is a thin layer of concentrated ozone which plays an essential role in protecting the Earth from dangerous solar radiation. It acts as a giant sponge and absorbs the vast majority of the sun's dangerous Ultraviolet Light. 

(The ozone layer is too large a topic for this article, but you can read more about it in the  following post.) 

One of the most surprising things about the stratosphere is not its characteristics but about what you find in this layer. Certain bird species like the common crane, whooper swan, and the Rüppel's griffon vulture are capable of flying in the lower stratosphere.

Although it is situated above the upper reaches of conventional aircraft, scientists are still able to study it through the use of weather balloons, high-altitude aircraft, and also weather (sounding) rockets.

Air circulation within the stratosphere is dominated by the Brewer-Dobson Circulation, which is a single-celled air movement that stretches from the Poles to the Equator.

Facts About The Stratosphere

The following list highlights the characteristics and facts of the stratosphere in more detail.

  1. 1
    The stratosphere is the second layer of the atmosphere (above the troposphere.)
  2. 2
    It extends from a height of approximately 10 km (6 miles) to 50 km (30 miles) above the Earth's surface.
  3. 3
    It borders the troposphere below through a thin transitional space called the tropopause.
  4. 4
    It borders the mesosphere above through a thin transitional space called the stratopause.
  5. 5
    It is the only layer of the atmosphere where temperature inversion occurs (a drop in temperature as altitude increases.)
  6. 6
    The air in the stratosphere is about 1000 thinner than the air at sea level in the troposphere.
  7. 7
    The ozone layer is situated within this layer.
  8. 8
    Commercial airliners fly in the lower stratosphere to avoid the weather, travel faster, and save fuel.
  9. 9
    Polar Stratospheric Clouds develop in this layer near the poles at an altitude of 15 - 25 kilometers (9 - 15 miles) during the winter.
  10. 10
    Brewer-Dobson Circulation occurs in the stratosphere.
  11. 11
    The layer is approximately 35 kilometers (22 miles) thick.
  12. 12
    Certain swans, cranes, and vultures can fly in the lower stratosphere. 

This list does not contain all the data available about the stratosphere but highlights the key facts and characteristics of this layer.

Conclusion

As this article clearly illustrated, the stratosphere has a crucial role to play in maintaining the atmosphere and all life in it.

It sets it apart from the other atmospheric layers by temperature rising instead of dropping as altitude increases, a process called temperature inversion.

The importance of the stratosphere is highlighted by the presence of the ozone layer, without which no life on Earth will be possible.

If you are interested in the complete structure and make-up of the atmosphere, this article covers all five atmospheric layers and their relation to each other in more detail.

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!

Wessel

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Facts About The Mesosphere

Facts About The Mesosphere

The atmosphere consists of five distinct layers, with the mesosphere being one of them. But what exactly is the mesosphere, and what are its characteristics?

The mesosphere is one of the 5 layers of the atmosphere, situated above the stratosphere and below the thermosphere at an altitude of 50 km (30 miles) to 85 km (53 miles). It is the coldest of the atmospheric layers and the part of the atmosphere in which meteoroids and space debris burn up.

Although our atmosphere looks like one continuous piece of sky, it is made up out of five distinctly different layers: The troposphere, stratosphere, mesosphere, thermosphere, and exosphere. In this post, we focus on the mesosphere, Earth's third most outer layer. 

This article not only examines what the mesosphere is but also look at the characteristics or facts that define it.

Mesosphere Definition

mesosphere structure

The mesosphere is situated just above the stratosphere, with a thin layer of air called the stratopause separating the two layers.

Like the other atmospheric layers, it does not have a fixed height but starts at an altitude of approximately 65 km (40 miles), extending up to a height of roughly 85 km (53 miles)

It is also the coldest of the five layers with its upper boundary, called the mesosphere, reaching temperatures as low as -90° Celsius (-130° Fahrenheit). This region is the coldest part of the planet's atmosphere.

Temperatures drop as altitude increases in this space, unlike the stratosphere, which is characterized by temperature inversion (a rise in temperature as altitude increases.)

"Mesosphere" is derived from the Greek word mesos sphaira, meaning "middle sphere." It is a very apt description since the mesosphere is situated in the middle of the five layers (with the troposphere and stratosphere below, and thermosphere and exosphere above it.)

Scientists know very little about this layer since it lies at a height above the upper limits of conventional aircraft but below the region where low-orbiting satellites can operate. One of the only ways to study this part of the atmosphere is by using sounding rockets.

(You can learn more about sounding/weather rockets in this article.)

Meteor Shower

What we do know, however, is that it is within this layer that the vast majority of meteoroids and space debris burn up. As a result, the mesosphere contains a fairly high amount of iron and other metallic particles.

Another feature of the mesosphere is the presence of atmospheric tides and planetary waves. These waves start in the troposphere and eventually spreads into the mesosphere.

(In the mesosphere, the waves/tides become unstable and dissipate, creating momentum in the process. It is this momentum that drives global circulation to a great extent.)

Although almost all weather-related activity is limited to the troposphere, a rare weather phenomenon called noctilucent clouds can be found in this layer at a height of approximately 80 km (50 miles.)

Facts About The Mesosphere

The following list highlights the characteristics and facts of the mesosphere in more detail.

  1. 1
    The mesosphere is the third layer of the atmosphere (above the troposphere and stratosphere.)
  2. 2
    It extends from a height of approximately 65 km (40 miles) to 85 km (53 miles) above the Earth's surface.
  3. 3
    It borders the stratosphere below through a thin transitional space called the stratopause.
  4. 4
    It borders the thermosphere above through a thin transitional space called the mesopause.
  5. 5
    It is characterized by a drop in temperature as altitude increases.
  6. 6
    It is the coldest of the five atmospheric layers, with temperatures dropping to -90° Celsius (-130° Fahrenheit) in the mesopause.
  7. 7
    Meteoroids and other small space debris burn up in this layer.
  8. 8
    sodium layer 5 kilometers (3.1 miles) thick can be found in the upper regions of the mesosphere. 
  9. 9
    Electrical discharges, called lightning sprites (also know as ELVES or red sprites), are visual phenomena that occur in the mesosphere.
  10. 10
    A rare visual phenomenon called noctilucent clouds occurs at a height of approximately 80 kilometers (50 miles) in the upper mesosphere.
  11. 11
    Although not as effective as the stratosphere, a significant amount of solar radiation is also absorbed in this layer.
  12. 12
    Combined with the stratosphere, it is often referred to as the Middle Atmosphere.
  13. 13
    It is the least known of all layers due to its limited accessibility.

This list does not contain all the data available about the mesosphere but highlights the key facts and characteristics of this layer.

Conclusion

Although it may be the least-known layer in the atmosphere, as this article illustrated, a fair amount of valuable information has already been obtained to help better understand the mesosphere and its importance much better.  

The third and coldest layer of the atmosphere has just an important part to play as any of the other four atmospheric layers. This article highlighted the importance of the mesosphere, as well as examining its defining characteristics.

If you are interested in the complete structure and make-up of the atmosphere, this article covers all five atmospheric layers and their relation to each other in more detail.

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

Until next time, keep your eye on the weather!

Wessel

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Difference Between Land Breeze And Sea Breeze

Difference Between Land Breeze And Sea Breeze

You may have heard about a land breeze and sea breeze, especially during weather forecasts when weather near the coast is discussed. But what exactly is the difference between them?

A land breeze blows from the land towards the sea during the evening as a result of the ground cooling down faster than the adjacent water surface, while a sea breeze blows from the sea towards the land during the day as a result of the ground warming up faster than the adjacent water surface.

This definition, though, only scratches the surface of how and why these two weather occurrences differ. This article takes a closer look at each meteorological phenomenon, what they are, and how they develop to better understand their differences.

What Is A Land Breeze?

Land Breeze

A land breeze is a wind that forms where the land and a large body of water meet. It usually occurs overnight and early morning when the land bordering the water cools down faster than the water's surface. The resulting wind blows from the land towards the water.

Like a sea breeze, a land breeze does not only occur on the coast between the land and sea but on the boundary where any piece of land and a large body of water meet. This includes lakes, large dams, and inland seas.

Since a land breeze originates over land, it is generally relatively dry and contains less moisture (humidity) than a sea breeze that originates over water where more evaporation takes place. 

Exactly why a land breeze blows towards the water and occurs during the evening can best be explained by looking at its development.

How A Land Breeze Form

The following steps show how a land breeze develops, which will help to explain its unique behavior compared to a sea breeze. 

  1. 1
    After sunset, both the land and the sea start cooling down. The characteristics of the land surface allow it to cool down more rapidly than the body of water.
  2. 2
    As a result, a high-pressure system forms overland, while the warmer surface water leads to the formation of a low-pressure system over the bordering body of water.
  3. 3
    Wind always blows from an area of high pressure to an area of low pressure. This means that the wind blows from the land towards the water during this period.
  4. 4
    The resulting dry wind that blows from the shore towards the body of water is called a land breeze (also known as offshore wind).

As will be illustrated later on in this post, the opposite takes place during the formation of a sea breeze.

What Is A Sea Breeze

Sea Breeze

A sea breeze is a wind that forms where the land and a large body of water meet. It usually occurs during the day and early evening when the land bordering the water warms up faster than the water's surface. The resulting wind blows from the water towards the land.

Like a land breeze, a sea breeze does not only occur on the coast between the land and sea but on the boundary where any piece of land and a large body of water meet. This includes lakes, large dams, and inland seas.

Since a sea breeze originates over water, it contains more moisture (humidity) as a result of evaporation, compared to a land breeze that is relatively dry due to its formation over land. 

Exactly why a sea breeze blows towards the land and occurs during the day can best be explained by looking at its development.

How A Sea Breeze Form

The following steps show how a sea breeze develops, which will help to explain its unique behavior compared to a sea breeze.

  1. 1
    After sunrise, both the land and the sea start to heat up. The characteristics of the land surface allow it to warm more rapidly than the body of water.
  2. 2
    As a result, a low-pressure system forms overland, while the warmer surface water leads to the formation of a high-pressure system over the bordering body of water.
  3. 3
    Wind always blows from an area of high pressure to an area of low pressure. This means that the wind blows from the water towards the land during this period.
  4. 4
    The resulting humid wind that blows from the body of water towards the shore is called a sea breeze (also known as onshore wind).

Offshore Wind vs Onshore Wind

The following diagram highlights the key differences between a land and sea breeze.

Land Breeze

Sea Breeze

Blows from the land towards a body of water.

Blows from a body of water towards the land.

A high-pressure system forms over land.

A low-pressure system forms over land.

A low-pressure system forms over the surface water.

A high-pressure system forms over the surface water.

Occurs during the evening and early morning.

Occurs during the day and early evening.

Contains less moisture (humidity) than a sea breeze.

Contains more moisture (humidity) than a land breeze.

Also known as an offshore wind.

Also known as an onshore wind.

Conclusion

Although both a land and sea breeze occur on the boundary between a stretch of land and a body of water, this is where the similarity between the two phenomena ends.

The characteristics of a solid piece of land allow it to warm up and cool down much faster than a large body of water that reacts much slower. 

It is these dramatically different characteristics that allow for the formation of a land breeze during the evenings and a sea breeze during the day.

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!

Wessel

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