Air Mass

|Definition | Overview | Types | Maritime Arctic | Continental polar | Maritime polar | Continental tropical |Maritime tropical |Movement and Fronts | Modification |

1. Definition:

An Air Mass that has pressure, humidity, and temperature values that are horizontally uniform.

An air mass is a significant amount of air that is usually the same temperature and pressure. Different pressures and temperatures indicated unstable air mass. Storms can be caused by instability, such as this one over the German North Sea.

2. Overview:

An air mass is a significant portion of the atmosphere that has a largely constant temperature and moisture content. Air mass can spread up to 16 km into the atmosphere, and can flow thousands of kilometers in either direction.

The production of air mass is known as source zones, which are large, humid, and evenly cooled regions. Low wind speeds let air stay stable for a long time and adopt the temperature or other properties of the source place.

When wind moves air mass, meteorological conditions (hot or cold, dry or moist) are transferred from the source region to the target region. As it moves into a new place, the air mass can meet with another air mass that has a different humidity level and temperature.

According to where they form across Earth, meteorologists may distinguish different air masses. Air mass falls into these four types, maritime arctic, continental polar, maritime polar, continental tropical, and maritime tropical.

Polar air masses are extremely frigid and from there. Tropical air masses start in low-latitude areas and are only fairly hot. High-latitude areas are where chilly polar air mass form. Warm tropical air mass forms close to the equator.

Moreover, air masses are classified according to whether they occur over land or sea. Maritime air masses are humid and develop over water. A dry continental air mass is generated over land.

Because it is cold and dry, the air mass that forms over northern Canada is known as a regional polar air mass. A maritime tropical air mass is one that develops over the Indian Ocean and is hot and humid.

3. Types of Air Mass:

There are five different types of air mass:

  • Maritime arctic
  • Continental polar
  • Maritime polar
  • Continental tropical
  • Maritime tropical

3.1.Maritime Arctic Air Mass:

The properties of an arctic maritime air mass are similar to those of a polar maritime air mass, but the air is cold and less humid due to the shorter sea range.

Even though it doesn’t happen often in the summer, Arctic air can bring heavy rain or thunderstorms and unexpectedly cold temperatures.

In Scotland and along the coasts exposed to northerly winds, hail, and snowstorms are most common between October and May when the air is cold enough to generate them.

Above the North Pole and the Arctic Ocean, an arctic maritime air mass forms.

Occasionally, widespread and heavy snowfall can result from polar low-pressure systems that arise in this air mass, but typically, inland areas are cloud-free during the winter. Arctic maritime is typically the coldest air mass across northern Scotland, but it is not as cold as polar continental over the majority of Britain.

3.2. Continental Polar Air Mass:

This air mass is only thought to occur throughout the winter (November to April), and it originates above the snow fields of Eastern Europe and Russia.

This air mass would be categorized as tropical continental during the summer when the land mass is significantly warmer.

The weather qualities of this air mass depend on how long of a sea track it takes to travel from Europe to the British Isles. Because this air is naturally very cold and dry, if it travels only a short distance over the English Channel to reach southern Britain, the weather is characterized by clear skies and severe winters. Longer sea tracks over the North Sea make the air more unstable and add moisture, which causes snow or rainstorms, particularly close to the east coast of Britain.

This air mass typically has the coldest temperatures in the British Isles, dropping below -10 °C at night and occasionally staying below zero throughout the day.

3.3. Maritime Polar Air Mass:

This air mass originates over northern Canada and Greenland and travels north-westerly till it reaches the British Isles.

The air mass that affects the British Isles most frequently is polar maritime. This air mass begins extremely cold and dry, but as it travels over the lengthy, relatively hot waters of the North Atlantic, its temperature quickly rises and it becomes deeply unstable.

Whatever time of year, this air mass is known for its regular showers. Hail and thunder are frequent across a large portion of the western and northern sides of the British Isles during the winter months when instability (convection) is most active over the sea.

However, due to lower surface heating, eastern Britain might have fewer spots of rain. The opposite is true in the summer when eastern England experiences the greatest rainfall and land temperatures rise above sea levels.

3.4. Continental Tropical Air Mass:

This air mass comes from the Desert and North Africa (a warm source region). Although it can develop at other times of the year, it is most often in the summer months of June, July, and August.

Tropical continental air typically influences our greatest temperatures, which are over 30 °C during the day and 15 to 20 °C at night.

Due to contaminants picked up in the air during its transit over Europe and sand particles carried in the air by Saharan dust storms, visibility is typically moderate to poor. Sometimes, rains may wash away the Desert dust, leaving behind colored rain and a thin film of orange dust on cars.

3.5. Maritime Tropical Air Mass:

Warm seas of the Atlantic Ocean between the Azores and Bermuda are where this air mass originates. In a tropical marine air mass, the south-westerly direction of the wind is the prevailing wind direction from across the British Isles.

Tropical maritime air is warm and humid in its lowest layers and, while instability over its source region, becomes stable and the air gets saturated throughout its transit over cooler waters. As a result, low clouds, drizzle, and maybe fog along windward shores and across hills are brought to the British Isles by tropical maritime air masses.

Yet, the cloud may break up under the lee of high ground, where the weather, especially in the summer, might be bright and sunny. A few degrees above average air temperature can be achieved by this gentle air stream, especially during the winter months.

4. Movement and Fronts of Air Mass:

A weather front, which is the main cause of meteorological phenomena, is a boundary dividing masses of air with varying densities. Depending on the type of front, fronts are represented in surface weather assessments using a variety of colored lines and symbols. Temperature and humidity are typically different between the air masses separated by a front.

Cold fronts can occasionally be preceded by squall lines or dry lines and can include limited areas of severe weather. In most cases, stratiform precipitation and fog occur before warm fronts. After a front has passed, the weather typically clears up fast. Even though there is always a change in wind direction, some fronts produce little to no rainfall and little cloud cover.

Warm fronts travel poleward, while cold fronts and occluded fronts typically move from west to east. Cold fronts and cold occlusions travel more quickly than warm fronts and warm occlusions due to the denser air in their wake. Frontal migration can be slowed by mountains and warm water.

A front can disintegrate into a shear line, which divides areas with different wind speeds when it becomes stationary and the concentration contrast across the frontal boundary disappears. Over the wide open ocean, this is most typical.

5. Modification:

There are several techniques to alter air masses. Surface flux from below-surface vegetation, such as a forest, works to wet the air mass above. At distances as small as 35 to 40 kilometers, heat from beneath warmer waters can significantly alter an air mass.

For instance, small lake-effect snow bands can form southwest of extratropical storms when curved cyclonic flow transports cold air through unusually warm water bodies.

Since lakes and other big bodies of water effectively store heat, there are considerable temperature variations (more than 13 °C or 23 °F) between the water’s surface and the air above, which causes severe localized precipitation in those bands.

The warmth and moisture are carried upward as a result of this temperature differential, condensing into vertically oriented clouds (see satellite image), which induce snow showers. Both the water temperature and the large-scale environment have a direct impact on the temperature decrease with height and cloud depth.

The intensity of the temperature drop with height, the depth of the clouds, and the amount of precipitation are all inversely correlated.

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