CLIMATOLOGY-3

                     CLIMATOLOGY

1.1 GENERAL CIRCULATION OF THE ATMOSPHERE 

1.2 AIR MASSES

1.3  FORNTS

1.1 GENERAL CIRCULATION OF THE ATMOSPHERE:

The general circulation of the atmosphere refers to the large-scale patterns of atmospheric motion that persist over time. These patterns are driven by the uneven distribution of solar radiation on Earth's surface, which creates variations in temperature and pressure. The primary factors influencing the general circulation include the rotation of the Earth, the distribution of land and water, and the heat-trapping properties of the atmosphere.

The key features of the general circulation include:

1. Equatorial Low Pressure Belt (Intertropical Convergence Zone - ITCZ): Near the equator, solar radiation is most intense, leading to warming and the ascent of moist air. This area is characterized by low pressure and is known as the ITCZ. It is a region of frequent thunderstorms and heavy rainfall.

2. Subtropical High-Pressure Belts: As air rises in the equatorial region, it moves poleward aloft and descends around 30 degrees latitude in both hemispheres, forming subtropical high-pressure belts. These areas are characterized by dry conditions and are associated with desert regions such as the Sahara Desert in Africa and the Sonoran Desert in North America.

3. Trade Winds: Surface winds that converge at the equator due to the Coriolis effect are known as trade winds. They blow from east to west in the tropics, converging near the equator to replace the rising air in the ITCZ.

4. Westerlies: Between 30 and 60 degrees latitude, the surface winds are westerlies, flowing from west to east. These winds are influenced by the Coriolis effect and the temperature differences between the subtropical high-pressure belts and the subpolar low-pressure areas.

5. Subpolar Low-Pressure Areas: Near 60 degrees latitude in both hemispheres, the westerlies encounter the polar easterlies, creating a region of low pressure. This is known as the subpolar low-pressure area.

6. Polar Easterlies: In polar regions, surface winds are generally easterlies, flowing from east to west. These winds are a result of the temperature difference between polar regions and the subpolar low-pressure areas.

7. Polar High-Pressure Areas: Near the poles, cold air descends, creating high-pressure areas. These regions are known as the polar high-pressure areas.

These large-scale circulation patterns form the basis for the Earth's climate and weather systems. While the general circulation provides a broad framework, regional and local factors also play a significant role in shaping specific weather patterns. The interaction between these various atmospheric components results in the diverse climates experienced across the globe.

1.2 AIR MASSES:

Air masses are large bodies of air with relatively uniform temperature, humidity, and pressure characteristics. These masses can cover large areas and extend vertically throughout the troposphere, influencing the weather patterns of the regions they move into. The characteristics of an air mass are determined by the geographical region over which it forms, called its source region.

There are four primary types of air masses, categorized based on their temperature and humidity characteristics:

1. Maritime Tropical (mT):

   - Source Region: Over warm ocean waters, typically in the tropical or subtropical regions.

   - Characteristics: Warm and humid.

   - Effect: When maritime tropical air masses move over land, they can bring warm temperatures and moisture, contributing to the development of thunderstorms and heavy rainfall.

2. Continental Tropical (cT):

   - Source Region: Over hot, dry land areas, often in the subtropics or deserts.

   - Characteristics: Hot and dry.

   - Effect: Continental tropical air masses can bring very hot and dry conditions to regions they influence, contributing to the development of heatwaves.

3. Maritime Polar (mP):

   - Source Region: Over cold ocean waters, usually in higher latitudes.

   - Characteristics: Cool and humid.

   - Effect: Maritime polar air masses can bring cool temperatures and moisture, contributing to the development of clouds, precipitation, and sometimes snow when they move over land.

4. Continental Polar (cP):

   - Source Region: Over cold land areas, often in polar regions.

   - Characteristics: Cold and dry.

   - Effect: Continental polar air masses can bring cold temperatures and dry conditions to regions they influence, often leading to clear skies and cold weather.

The boundaries between air masses are called fronts, and the interactions along these fronts play a crucial role in the development of weather systems, such as low-pressure systems and storms. The clash between air masses with different temperature and humidity characteristics can lead to the lifting of air, condensation, and the formation of clouds and precipitation.

The classification of air masses and their movements are essential components of meteorology, helping meteorologists understand and predict weather patterns. As air masses interact and undergo modifications, they influence the day-to-day weather experienced in different regions.

1.3  FORNTS:

Fronts are boundaries between different air masses with distinct temperature, humidity, and density characteristics. The collision of these air masses along a front can lead to various weather phenomena, including the development of storms, precipitation, and changes in temperature. There are different types of fronts, each associated with specific weather conditions. The primary types of fronts include:

1. Cold Front:

   - Characteristics: A cold front forms when a cold air mass advances and replaces a warmer air mass.

   - Symbol: Represented on weather maps by a blue line with triangles pointing in the direction of the warm air it is displacing.

   - Weather Effects:As a cold front passes through an area, it can bring abrupt changes in weather conditions. Common effects include the rapid onset of heavy showers or thunderstorms, followed by cooler temperatures and clearing skies.

2. Warm Front:

   - Characteristics: A warm front forms when a warm air mass advances and rises over a cold air mass.

   - Symbol: Represented on weather maps by a red line with semicircles pointing in the direction of the cold air it is replacing.

   - Weather Effects: Warm fronts are associated with more gradual weather changes. They often bring overcast skies, steady precipitation, and a gradual increase in temperature.

3. Stationary Front:

   - Characteristics: A stationary front occurs when two air masses meet but neither advances over the other.

   - Symbol: Represented on weather maps by alternating blue triangles and red semicircles on opposite sides of the line.

   - Weather Effects: Stationary fronts can lead to prolonged periods of cloudy weather and precipitation. The intensity of the weather depends on the specific conditions at the front.

4. Occluded Front:

   - Characteristics: An occluded front forms when a fast-moving cold front catches up with a slow-moving warm front.

   - Symbol: Represented on weather maps by a purple line with alternating triangles and semicircles, indicating both cold and warm air masses involved.

   - Weather Effects: Occluded fronts can bring a mix of weather conditions, including precipitation and cooler temperatures. The weather associated with an occluded front depends on the characteristics of the air masses involved.

Frontal boundaries are crucial in the development and evolution of weather systems. The lifting of air along fronts can lead to the formation of clouds and precipitation. Meteorologists use weather maps to track the position and movement of fronts, helping them forecast changes in weather patterns and the likelihood of specific weather events in different regions.