Category: Geography Notes PPT

In Geography, jet streams are defined as the fast-flowing air currents characterized by their narrow and meandering type current. The jet stream is prevalent in some planets including our planet Earth.

On Earth, main jet streams are located near the altitude of the tropopause region and are located in the western winds which are flowing west to east. The path of this wind has a typical meandering shape. Jet streams can start, stop, split into two, or can have more parts. While, at last, they combine into one single stream. 

On the same subject matter, we will present our discussion in an elaborate fashion.  

Subtropical Jet Stream 

The Subtropical jet stream is a belt of strong upper-level winds that lie above the regions of the subtropical high-pressure region. Unlike the polar front jet streams, this wind travels in the lower latitude regions and at a slightly higher elevated region, this is because of the increase in height of the tropopause layer at the lower latitudes. The temperature gradients of this jet stream do not extend to the surface area, for this reason, the surface front is not evident. While in the tropical region an easterly jet is at times found at upper levels. Mainly this wind is found when a landmass is located poleward of an ocean, for this reason, the temperature increases with the latitude.

Subtropical Westerly Jet Stream 

The name ‘Subtropical Westerly Jet stream’ is located over 27-degree to 30-degree north latitude. In our country, the jet streams blow south of the Himalayas. This wind blows in India all through the year except in the summertime. The north and the north-western parts of the country experience western cyclonic disturbances, this happens for the westerly flow in the wintertime. While in summertime the subtropical westerly jet streams move northwards towards the Himalayas with the movement of the sun.   

The Western disturbances abbreviated as WDS are the mid-tropospheric to upper‐tropospheric mesoscale vortices. They typically propagate along with the subtropical westerly jet stream. This brings heavy rainfall in the country, Pakistan, and in northern India during the boreal winter.

They act similarly to the Tibetan Plateau vortices (TPVs). This wind also affects southwest China during the springtime and in the summer season. This wind originates from the Tibetan Plateau. 

The similarity implies the existence of a general group of upper‐tropospheric vortices that features interactions with the orography of the Hindu Kush‐Himalaya‐Tibetan Plateau region.

Equatorial Jet Stream

The Jet streams are the narrow bands of strong and gusty winds blowing in the upper levels of the atmosphere. Normally the jet streams blow from east to west, but at times it often shifts to north and south as well. Like any other winds, the jet streams follow the boundaries between the hot and cold air. The cold and hot boundaries are characterized in the wintertime. The jet streams are the strongest in both the northern and the southern hemisphere. 

The Daunting Question is, why does the Wind Blow from West to East?

To recollect from our previous study, if the earth did not rotate, the global winds, the warm air at the equator would drift towards both the polar regions. Hence, we see that the earth’s rotation has divided the wind circulation into three cells. The rotation of the planet is also responsible for the cause of jet streams. 

When the wind moves away from the equatorial region, the motion of the air is not directed towards north and south but it is affected by the momentum as it drifts away from the equator. This is reasoned out for the momentum of how fast a location present on or above the earth moves relative to the earth’s axis. 

Your location will determine the speed relative to the earth’s axis. If you stand on the equator, and your friend is standing on a 45-degree latitude line, you will find miraculously that you move faster than your friend. While another friend, suppose standing on the pole will not move at all. While he or she will only spin standing on the pole. This speed of rotation is great enough to lower the weight up to one pound if standing on the pole than on the equator.   

What Causes Jet Stream?

We need to understand this fact, that the Sun doesn’t heat the entire earth evenly, at some places it heats more like in the equator, the sun is unbearable. While, at some places, the sun rays may not reach properly, like in the polar regions. For this very reason, the areas near the equator are quite hot and the areas near the poles are very cold.

So, when the Earth’s warmer air masses meet or collide with the cooler air masses, the warmer air rises higher in the atmosphere while the cooler air sinks to replace the warm air which rose above. This movement creates an air current, or wind to gush down. This forms the jet stream. 

On Our Planet, There are Four Jet Streams. 

The Jet streams are formed in the atmosphere when the warm air masses meet the cool air masses. 

On average, jet streams blow at about 110 miles per hour, calculated approximately. The temperature difference between warm and cold air masses is quite dramatic then it will cause the jet streams to move speedier, which can be 250 miles per hour. 

The term thermohaline circulation is related to oceanography. Oceanography refers to the study of the physical, chemical, biological and historical properties of the ocean. Thermohaline circulation is a phenomenon in which the circulation of the component of oceanic water takes place due to temperature as well as salinity gradient. Thermohaline circulation is also known as Global Ocean Conveyor or Great Ocean Conveyor Belt as it controls the circulation components of ocean water worldwide. Thermohaline circulation suggests the replacement of surface seawater with seawater at depth. Thus it indicates the vertical flow of seawater from surface to bottom and such kind of flow is very slow.

What is Thermohaline Circulation?

To define thermohaline meaning, the term thermohaline can be divided into two parts “thermo” and “haline” which refer to temperature and salt content respectively. Thus the term thermohaline circulation indicates the involvement of temperature and salinity with this oceanic phenomenon.  Thermohaline circulation is a slow process but it involves a movement of huge amounts of water that carries heat, salts and other nutrients of seawater.

Such an ocean conveyor belt makes the warmer surface seawaters move from subtropics to poleward.

Characteristics of Thermohaline Circulation

Oceanic circulation can be divided into two kinds: wind-driven circulation and thermohaline circulation. Wind-driven circulation involves the horizontal movement of surface seawater with the help of wind current and it generates large gyres on the ocean. In contrast, thermohaline circulation is much sluggish and involves the vertical movement of seawater predominantly. It is observed that such circulation has a typical speed of 1 centimetre per second but it involves a movement of huge amounts of water that carries heat, salts and other nutrients of seawater. 

The concentration of seawater largely depends on the temperature and salt content of water. Concentration decreases with an increase in temperature and a decrease in the salt content of water in that particular region. Thus temperature and salinity control such kind of ocean conveyor belt from one location to another.

Basis of Thermohaline Circulation

Temperature and salinity are the main driving force of such circulation of seawater. During the winter season, the surface water becomes denser due to cooling and net evaporation that is why it sinks to the deeper region of the ocean and spreads slowly. Seawater at depth replaces the surface water that sinks. That is how the thermohaline circulation takes place. Henry Stommel and Arnold Arons in 1960 first developed the theory of thermohaline circulation pattern.

Sometimes temperature difference makes such kind of flow of seawater in a horizontal direction also. For example, warmer surface seawaters move from subtropics to poleward which controls the climate of Iceland and other coastal areas of Europe.

Global Warming and Thermohaline Circulation

Global warming is a phenomenon that increases the average temperature of the earth due to the excessive addition of heat-trapping greenhouse gases like carbon dioxide, methane, nitrogen dioxide, etc. Global warming is the major reason for worldwide climate change. According to scientists, global warming can impose a major impact on the Great Ocean Conveyor Belt. Due to the increase of the average global temperature the glacier and the ice sheets in the polar region are melting and creating a huge influx of freshwater in the ocean. 

Freshwater addition makes the surface seawater less dense as a result the sinking process of surface water is inhibited. Thus such a phenomenon can even shut down oceanic thermohaline circulation. Scientists predict that such a stoppage of thermohaline circulation can trigger colder conditions in polar regions. Moreover, a stoppage in circulation makes a large impact on the oceanic ecosystem due to the stoppage of the nutrient cycle as well.

Did You Know?

1.Henry Stommel and Arnold Arons in 1960 first developed the theory of thermohaline circulation pattern.

2.The term thermohaline can be divided into two parts “thermo” and “haline” which refer to temperature and salt content respectively.

3.Sometimes temperature difference makes such kind of flow of seawater in a horizontal direction also. For example, warmer surface seawaters move from subtropics to poleward which controls the climate of Iceland and other coastal areas of Europe.

Conclusion

Thermohaline circulation is an oceanic phenomenon that involves the vertical flow of seawater in a bulk due to the temperature and salinity gradient. Such a slow bulk flow helps in the circulation of nutrients and other biological matters of seawater. Thus thermohaline circulation on nutrient cycle and coastal climate.  

The temperature of the earth is changing day by day. Have you ever wondered how we are surviving on Earth? The answer to this question is the presence of tropical rainforest on our planet which covers less than 2% of the surface of the Earth but plays a huge role in maintaining the ecological balance and the environment of the whole planet. These forests are the source of oxygen, plants and other species, minerals, etc. Without these equatorial forests survival on the Earth would not be possible. In this article, we will be discussing the tropical rainforest biome. We will cover all the related concepts such as percentage of their features, meaning or definitions, location or distribution, climate or temperature, plants or animals, minerals, agriculture, etc. This article will help you to understand one of the biomes of the earth and will help in understanding the important forests of the world. 

 

Tropical Forest

They come under the ” Af ” category according to Koeppen’s Classification of Climate which refers to Tropical wet climate. The tropical rainforest biome is the area that covers only around 6% of the area of the Earth but it covers around 50% of the species and has tall trees, has a dense canopy and receives maximum rainfall. These forests are also known as,

• Equatorial Rainforests

• Equatorial Evergreen Forests

• Tropical Moist Broadleaf Forests

• Lowland Equatorial Evergreen Rainforest

 

()

 

Definition

The definitions of tropical rainforest are given below:

According to the Oxford dictionary, ” rainforest means ​a thick forest in tropical parts of the world that have a lot of rain.”

 

According to the Cambridge dictionary, ” tropical rainforest means thick forest that grows in hot parts of the world.”

 

Features

• The biotic and abiotic factors depend on each other. A minor change in one area will affect the other.

• These areas have huge biodiversity.

• The temperature is almost the same the whole year and never comes below 20°C and exceeds 35°C rarely.

• There are no seasons and a hot or humid atmosphere is found here.

• Rainfall occurs a lot here thus the soil is not so fertile here because most of the nutrients are washed away due to rainfall.

• The forests have a dense canopy here and sunlight does not reach the ground.

• They have different layers such as the ground level, the shrubs, the under and main canopy, and the emergents.

 

()

Tropical Rainforest Location

 

()

These forests are found in between the tropics ie. Tropic of Cancer and Tropic of Capricorn. These are mainly found in South America, Western or Central Africa, India and Southeast Asia, and some other areas. The extent of their distribution can be seen on the map.

 

Information on Rainfall Distribution and Characteristics

There are certain aspects of tropical rainforests that are the same no matter which rainforest it is.

• Tropics are the home of rainforests.

• At least 80 inches (200 cm) of rainfall each year falls on rainforests.

• There is a canopy in a rainforest, which consists of a layer of branches and leaves that form 30 metres (100 feet) off the ground between two trees closely spaced. Forest plants and animals depend heavily on the canopy for survival.

• Forests have an extraordinary amount of biological diversity, or “biodiversity”. The Earth’s rainforests are home to roughly half of Earth’s terrestrial species.

 

At local, regional, and global scales, rainforests provide ecosystem services, among them the production of oxygen (tropical forests account for 25-30 per cent of the world’s oxygen turnover) and the storage of carbon (tropical forests store an estimated 229-247 billion tonnes of carbon). They also significantly affect precipitation patterns and weather patterns; modulate flood and drought cycles, and facilitate nutrient cycling.

 

Tropical Rainforest Climate

These areas are dominated by maritime tropical air masses and usually have the same temperature over the year. The average monthly temperature found here is 27°C which does not vary so much. The temperature is always moderate due to the presence of clouds or precipitation or regular sea and land breezes. Average annual rainfall in these areas is always above 150cm and can be around 250cm to 300cm in some areas. There is no winter and no month without rainfall. 

 

Vegetation and Species

The favourable conditions of these areas such as high temperature along with continuous rainfall lead to tropical rainforests.

 

Tropical Rainforest Plants

The “Selvas” is the densest forest area found in the Amazon forests which has a very dense canopy. Evergreen trees can be found here such as mahogany, ebony, dyewoods, Kapok, rubber, etc. Other Plants in the rainforest such as orchids, ferns, bamboo, banana, cassava, avocado, etc. are also found in these areas. Besides these, Mangrove trees are found in the coastal areas.

 

Tropical Rainforest Animals

Various animal species are found here such as rhinoceros, tapir, gorilla, jaguar, African grey parrot, keel-billed toucan, spider monkey, sloth, hornbill, eagle, flying fox, etc.

 

Minerals

Various precious minerals are found here such as gold, copper, diamonds, and other gemstones. Besides these, they are also a great source of oil reserves as well. Extraction of these minerals or oil reserves here is a difficult task because it affects the natural ecosystem and environment a lot.

 

Life and Economy

These regions are sparsely populated. People like primitive ones and more advanced ones are used to practising shifting cultivation here. There is no problem or shortage of food as well and they do not need to stock food items for the future. Shifting cultivation is common where dense forests are found in the world. Even in India, in North East regions, this type of farming is practised. Besides farming, people do other commercial activities as well. Such as collection of wild rubber by the Indian tribes in the Amazon basin, nuts collection by the pygmies in the Congo basin, etc. The conditions of these areas are also favourable for products of industrial use such as the cultivation of natural rubber which has a great demand. Cocoa is also a very important crop which is grown here. Other important crops are coconuts, coffee, tea, tobacco, sugar, spices, etc. 

 

Tropical Rainforests India

India is an Asian country that also consists of tropical evergreen forests which are found in eastern or western ghats of the country and Northeast regions. For example, in Tamil Nadu, Kerala, Karnataka, Maharashtra, Assam, Arunachal Pradesh, Nagaland, Tripura, Meghalaya, West Bengal and Andaman & Nicobar Islands. These areas are rich in biodiversity and rainfall.

 

Did You Know?

• Rainforests are found in all the continents of the Earth except Antarctica because it does not provide favourable conditions for these forests.

• These forests are a blessing for our planet. The forests of Amazon are actually the lungs of the planet Earth and ¼ of the medicines are also found in these evergreen tropical forests.

• There was a time when 6 million sq. miles of these forests were found but not only less than half of it is remaining.

 

Conclusion

Thus, in this article, we have learned about evergreen forests or rainforests. Generally, there are two types of forests are found ie. tropical and temperate in which the tropical ones are the most distributed forests on our planet which support life on earth and maintain balance on the earth. We have learned what rainforests are, what are their other names, temperature or climate, distribution or location, plants or animals found here, agriculture or commercial activities and many other things. This article will help you understand the important biome along with its various features and will help the students of Class 8 and students of upper classes. This topic is important in various subjects such as Geography, Science and Environment.

 

Moist Forest vs. Evergreen Rainforest in Equal Temperatures

Tropical wet forests can be divided into two major categories: equatorial evergreen rainforest and moist rainforest, which includes monsoon rainforests and montane/cloud forests. Equatorial rainforests are characterised by averaging 80 inches (2,000 millimetres) of rain per year that is evenly distributed. There are tiers of vegetation within these forests with the highest levels of biological diversity. Tropical wet forests can be classified into one of three types, with equatorial forests constituting the majority.

Water bloom, they are the dense aquatic population. These are microscopic photosynthetic organisms that are produced by an excess of nutrient salts in the surface water, they bloom and breed on the water surface with adequate sunlight required for photosynthesis.

Water bloom is a cause of the rapid increase in the population of the algae which is responsible for the water body to change its own colour. This change is caused by a type of bacteria known as ‘cyanobacteria’. Thus, Water bloom gets its main origin from the blue-green algae which we will be further discussed. 

Water Bloom Meaning

As previously introduced, water bloom is the thick and dense aquatic population which are microscopic photosynthetic organisms. Water bloom breeds in the surface water due to excess nutrient salts on it, conditioned with sufficient sunlight for their photosynthesis. 

These microorganisms are actually toxic substances. Their release may discolour the water completely, and thus deplete its oxygen content. Further water bloom might poison the aquatic animals and the waterfowls, which are birds that swim in those water. Water bloom also irritates the skin and affects the respiratory tract of human beings. 

Single species of algae, diatoms, or the dinoflagellates, reproduce every after few hours. This will result in the dominance of their growing population. Approximately the number of individuals per liter (quart) of water may be from 1,000 to 60 million.

Algal Blooms 

An algal bloom is the speedy increase of the algae population. They originate in aquatic ecosystems. Algal bloom originates in fresh as well as in marine waters, and from here the name comes as – water bloom or the marine bloom, respectively. Algal bloom breeds well in an abundance of two types of nutrients – phosphorus and nitrogen. Their growth is usually caused by the runoff of nutrients like the dumping of animal waste, fertilizers or sewage from the farmlands.

Algal bloom constituents are mainly composed of bio-toxins and they are characterized by a distinct discolouration of the water due to large growth of pigmented algae cells. The colours of algal bloom range from green, red, brown, and yellow. The major types of algal blooms are cyanobacteria, which are the blue-green algae and the red tides, which are the red algal blooms.

Algal Bloom Treatment

Algal Bloom is a dangerous type of microorganisms, their growth will increase and enter into the food cycle if adequate measures are not assured. The toxic rate of the algal blooms is justified in the above-mentioned section, here we will see what are the ideal treatments for this algal bloom. Below mentioned is the treatment which is performed by the sewage system or by the government authorities to save the water life –

1. Proper Sewage Installation – 

In order to restrict the presence of nitrogen and the phosphorus constituent in water, firstly there is a need to treat the sewage water, as recommended by the waste treatment procedure. These are the five-step process that ensures optimal treatment of the sewage water.

2. To Make the Society Aware of the Pollution and Water Wastage –

To make the global environmental conservation goals a success, it should be started with individual initiatives only. Starting from minimizing the waste to reusing the waste and thus saving the environment is a big step to reduce the overall nutrient deposit into the water bodies. 

3. Use of Correct Fertilizer –

The fertilizers which have less nutrient constituent should be used by the farmers. The farmers should be advised by the agricultural experts about the dosage of fertilizers to be used which will not lead to contaminating of the water bodies. 

4. Treatment with Hydrogen Peroxide –

The compound which is found beneficial for the treatment of algal bloom is hydrogen peroxide which is effective for smaller water bodies.  

Blue – Green Algal Blooms

‘Bloom’ this term is used to indicate the rise in the algal cells to such an extent where they discolour the water, form scums and produce unpleasant tastes and odours. Blue-green algal affects the fish populations and also degrades the water quality. Accumulation of algae can cause depletion of oxygen which kills fish.

The Blue-Green Algae may Breed and Excessively increase in Water When:

• The nutrient levels, particularly phosphorus and nitrogen are in larger constituents to support the population growth.

• The ratio of nitrogen to phosphorus is low.

• It is standing water (lack of the mixing of the nutrients)

• The weather patterns are also stable. 

• The weather is basically warm.

The Blue-green algal blooms survive for several weeks, at times months, depending mainly on the weather. Cooler and windy weather may reduce or prevent the algal blooms to breed.

Wildlife refers to undomesticated animal species, but all animals that evolve or exist in the wild in an environment without human introduction have come to be included. In all habitats, biodiversity can be found. There are distinct types of wildlife in deserts, forests, rainforests, plains, grasslands, and other regions, including the most populated urban areas. Although the term generally applies to animals in popular culture that are unaffected by human influences, most scientists accept that human activities influence a great deal of wildlife.

To control the populations of different animal and bird species, forests and wildlife are important

Flora and Fauna 

You will be able to discover that several animals and plants are rare in your region if you look around. In fact, in terms of its vast array of biological diversity, India is one of the richest countries in the world. This is potentially two or three times the amount yet to be found. In our daily lives, these rich flora and fauna are so well incorporated that we take them for granted. But lately, mostly due to insensitivity to our climate, they are under great stress.

Different Plant and Animal Species

Natural Species: Species whose population levels, such as cattle, salt, pine, are considered normal for their survival.

Vulnerable Species: 

These are species whose population has decreased to levels that are likely to shift into the endangered category in the foreseeable future if the adverse factors continue to work. Blue sheep, Asian elephants, Gangetic dolphins, etc. are examples of such animals.

Rare Species: 

Small-populated species can shift into an endangered or vulnerable category if they continue to be affected by negative factors. The Himalayan brown bear, wild Asian buffalo, desert fox, and hornbill, etc, are examples of such animals.

Endemic Species: 

These are species that are typically separated by natural or geographical barriers only in some particular areas. The Andaman teal, the Nicobar pigeon, the Andaman wild pig, and the Mithun in Arunachal Pradesh are examples of such animals.

Extinct Species: 

These are species that do not exist despite looking for known or probable areas in which they may occur. A species from a local area, region, world, continent, or the entire earth may be extinct. The Asian cheetah and the pink head duck are examples of such species.

Types and Distribution of Forests and Wildlife Resources:

Classification of Forest:

• Reserved Forests

• Protected Forests

• Unclassed Forests

Conservation of Forest and Wildlife in India:

Conservation protects the natural diversity of water, air, and soil and our life support systems. It also protects plant and animal genetic diversity for better species and breeding development. In 1972, the Indian Wildlife (Protection) Act was passed, with various habitat protection provisions. A list of protected species was also released for all of India. The geographical condition of India and various climatic features have endowed the country with a large range of biological communities. Neither forest policy nor forest laws paid much respect to wildlife in the early years of forest conservation. The wildlife was ‘game’ and abundant. At the cost of community forests, the food crisis of the Second World War gave rise to an expansion of agriculture. Land allocation gained an extra social hue with independence-land for the landless-and even reserve forests were not spared. If it had not been for the activities of some ardent friends of wildlife, the scope of destruction would have been much greater.

Project Tiger: 

Tiger is one of the major species of wildlife in the network of fauna. The authorities realized that, at the turn of the century, the tiger population had declined to 1,827 from an estimated 55,000. In 1973, Project Tiger, one of the world’s well-publicized wildlife projects, was launched. Tiger conservation has not only been seen as an attempt to protect tigers. Save a species that is endangered, but with equal meaning as a way of retaining biotypes of major magnitude. The goal of forest cover in India is to cross 33 percent of the land area, but in terms of biodiversity and wildlife protection, forests within the Protected Areas have unique significance. Years ago, a report on Indian tiger reserves by the Zoological Survey of India showed how tiger reserves have contributed to the country’s efforts to preserve biological diversity by protecting keystone species and forests. It should be noted that 70% of the world’s biodiversity has been reported so far from the forested region.

To conserve the ecological diversity and the water, soil, and air that are the life support systems, conservation is important. In 1972, the Indian Wildlife (Protection) Act was enacted with various habitat protection provisions and an all-India list of protected species was issued. Several initiatives for the conservation of specific animals were also declared by the central government and were seriously threatened.

In Meteorology, the air mass is the large body of air having nearly uniform characteristics of temperature and humidity at any given level of altitude. Such a mass has a distinct borderline and may outstretch hundreds or thousands of kilometers horizontally and sometimes as high as the troposphere ( about 10-18 km [ 6 -11] miles above the Earth’s surface. An air mass is formed whenever an atmosphere gets in touch with a large, relatively stable land or sea surface for long enough periods to receive the temperature and moisture of that surface. 

Air masses are commonly classified concerning the latitudes, and their continent or maritime source regions. Colder or freezing air masses are termed polar or arctic, whereas warmer air masses are deemed tropical. Maritime and monsoon air masses are moist whereas continental and superior air masses are dry. 

Air Mass Definition

“An air mass is defined as the large mass of air whose physical features such as moisture, temperature, lapse rate, and content are approximately uniform horizontally for hundreds of kilometers”.

According to A.N, Straheler, and A.H. Straheler (1978), a large body of air in which an upward rise of temperature and moisture are fairly uniform over a large area is known as an air mass. 

Types of Air Masses

The most common types of air masses are maritime polar(mP), maritime tropical (mT), continental tropical (cT), continental polar (cP), and continental arctic (cA).  

• Maritime Polar (mP) Air Mass– The maritime polar air mass is cold and humid originating from the oceans in the polar latitudes.

• Maritime Tropical (mT) – The maritime tropical air mass is warm and humid originating from the oceans in the tropics.

• Continental Polar (cP) – The continental polar air mass is cold and dry originating from land regions in the polar latitudes. 

• Continental Tropical (cT) – The continental tropical air mass is hot and dry originating from land in the tropics. 

• Continental Arctic (cA) – The continental arctic air  mass is dry originating from the North pole.

• Continental Antarctica (cAA) – The continental antarctic air mass is extremely cold and dry originating from land at the south pole.

Look at the image given below to observe from where these different types of air masses typically originate. 

Air Mass Creation

Air masses are developed when air is present to the surface over an extended period. This generally occurs at high temperatures with light winds. The area where air masses develop is known as the source area. Air masses over the warmer surface develop much faster than the colder surface because there is a weaker disturbance in the stable air over the cold surface. When the air masses get shifted from their source region, they change over time due to the surface and the area over which the air masses flow. 

Air Masses Movement

Air masses do not stay over their source location for a long period. As the weather pattern changes slightly, air mass gets shifted to a new location. Two things occur as the air mass moves towards a new location. First, as the air mass shifts over different surface characteristics, it begins changing. This process is known as air modification. For example, a maritime polar air mass that moves from the Pacific oceans over the mountains in the western continental US will sometimes dry as it crosses over the mountains, wash away its moisture, and warm over the land surface until it becomes the continental tropical air mass. The second thing that occurs when air mass moves is that they can hit the other air masses. When two air masses hit, a boundary known as the front is developed.

Did You Know?

• Maritime tropical air masses are often referred to as the trade air mass.

• Continental Polar masses are dry and cold because of their continental source regions. 

• The continental polar mass that affects North America develops over interior Canada.

• Colder air masses are known as polar or arctic whereas warmer air masses are known as tropical. 

• Five air masses that affect the United States around the time of a typical year are maritime polar, maritime tropical, continental polar, continental tropical, and continental arctic. 

• The stability of air mass can be represented using the third letter either ‘k’ ( air mass colder than the surface below it ) or ‘w’ ( air mass warmer than the surface below it).  An example of this can be a polar air mass blowing over the Gulf airstream, represented as cPk.