Test: Climatology - 3 - UPSC MCQ

• The Westerlies, anti-trades, are prevailing winds from the west towards the east in the middle latitudes between 30 and 60 degrees latitude. They originate from the high-pressure areas in the horse latitudes and tend towards the poles and steer extratropical cyclones in this general manner.

• The Westerlies are particularly strong, especially in the Southern Hemisphere, where there is less land in the middle southern latitudes to cause the flow pattern to amplify, or become more north-south oriented, which would slow the Westerlies.

• The strongest westerly winds in the middle latitudes can come in the Roaring Forties, between 40 and 50 degrees latitude. The Westerlies play an important role in carrying the warm, equatorial waters and winds to the western coasts of continents, especially in the Southern Hemisphere because of its vast oceanic expanse.

• Hot air rises at the Equator and is pushed towards the poles by cooler air travelling towards the Equator (an atmospheric circulation feature known as the Hadley cell).

• At about 30 degrees from the equator, the outward-travelling air sinks to lower altitudes, and continues towards the poles closer to the ground (the Ferrel Cell), then rises again from about 60 degrees as the air joins the Polar vortex.

• This travel in the 30 to 60-degree zone combines with the rotation of the Earth to move the air currents from west to east, creating westerly winds.

• So, if you are facing the sea, the wind will strike your face and continue to land.

• During the night, this happens. So, if you are facing the sea, the wind will strike your back and continue to the sea.

• It flows in the Southern slopes of Alps. It is a strong, cold, northwesterly wind that blows from southern France into the Gulf of Lion in the northern Mediterranean, with sustained high-speed winds.

• It flows in the Northern slopes of Alps. It is a rain shadow wind that results from the subsequent adiabatic warming of air that has dropped most of its moisture on windward slopes.

• It flows in African Deserts. It is a Mediterranean wind that comes from the Sahara and can reach hurricane speeds in North Africa and Southern Europe.

The wind is broadly divided into three types.

• Permanent winds - The trade winds, westerlies and easterlies, constantly blow throughout the year in a particular direction.

• Seasonal winds - Winds change their direction according to the seasons. For example, monsoons in India.

• Local winds - Winds blow only during a particular period of the day or year in a small area. For example, land and sea breeze, and loo.

• Continentality means that the more a place is surrounded by land, the more extreme its weather will be because land heats faster as compared to the sea.

• Opposed to this, closeness to the sea moderates weather because in the day the sea heats slower than land. This cool sea breeze blows across the land, thus reducing the day temperatures.

In the night the sea cools down slower. And the exact opposite happens. This keeps the temperature moderate.

• Water vapour capacity increases with temperature increase. At low temperatures, such as in Tundra regions, the air will hold very less moisture as it becomes more compact.

• Coastal regions generally have moderate temperatures, and the air already has a lot of moisture.

• The case of option (b) is also similar due to high rainfall and not so high temperatures.

• In hot subtropical deserts, you will notice that evaporation is very fast, as the air can contain a lot of water vapour due to the aridity and high temperature. So, (c) is the answer.

• The maximum capacity of air to hold water vapour depends on the temperature of the air. Warmer air is capable of holding more water vapour than cooler air is.

• This, however, does not mean that warmer air actually has more water vapour in it than cooler air. It just means that warmer air has a greater maximum capacity to hold water vapour than docs cooler air.

• There is an upper limit to the amount of water vapour that can be present in a given mass of air.

• The colour of any object depends on its ability to reflect selected wavelengths of light. Consequently, if the object does not reflect any colour, it appears black.

• The tiny droplets of water in rain clouds scatter the while light of the Sun. Red is scattered first, and violet the last.

• This happens at such a high altitude that no rays of the Sun reach the bottom of the cloud. Thus, we do not see the rays of the Sun, and this results in a dark effect. As normal clouds have no water, the light is not scattered and thus looks white.

• A mass of condensed minute water droplets or tiny ice crystals in free air at significant elevations is called cloud.

• As the clouds are formed over the surface of the Earth at some height, they take different shapes.

• Depending on their height, expanse, density and transparency or opacity, they are grouped into four types: (i) cirrus; (ii) cumulus; (iii) stratus; (iv) nimbus.

• Cirrus: Thin and detached clouds formed at high altitudes (8,000-12,000 m). These clouds have a feathery appearance and are always white in colour.

• Two patterns are broadly observed. One, rainfall reduces from coastal to interior areas. Second, as mentioned in the question, any moisture-laden winds from the ocean will first hit the coastal areas and then interior areas.

• Moisture would go on reducing as the wind advances further in. Poles receive lesser solar insolation, have lesser evaporation and rainfall. The reverse is true for the equator. So, (a) is correct. Jet streams do not play a significant role here, and so, option (d) can be neglected.

• Oceans receive lesser solar insolation per unit area due to the cloudiness over them. Clouds reflect solar insolation.

• Cyclones occur due to intense evaporation and the existence of the low-pressure zone. They are one of the phenomena associated with high rainfall on oceans, not its cause. Since there is more water in oceans and wind movement is unable to carry all cloudiness to land, rainfall is greater in oceans.

1. Equatorial belt (also evenly distributed)

2. Windward sides of the mountain

3. Western coasts of cool temperate zones (also evenly distributed)

4. Coastal areas of monsoon land

Types of Droughts

• Meteorological Drought: A situation where there is a prolonged period of inadequate rainfall that is characterised by an unfair distribution of the same over time and space.

• Agricultural Drought: Also known as soil moisture drought, characterised by low soil moisture that needs to support crops, leading to crop failure. Besides, if the gross cropped area under irrigation in a region is more than 30%, then that region is excluded from the category of drought-prone area.

• Hydrological Drought: If water availability in various storages and reservoirs such as aquifers, lakes and reservoirs falls below what the rainfall can refill.

• Ecological Drought: If a natural ecosystem's productivity falls because of water shortage and ecological distress, the ecosystem is induced to damage.

• Islands and coastal areas 10° to 20° north or south of the equator usually have a tropical marine climate. The ocean is the mam's influence in creating the tropical marine climate.

• The temperature ranges from 25 °C to 35°C. The trade winds blow all year round. The trade winds are moist, as they have passed over warm seas. Since they are easterlies, they cause greater precipitation on the eastern coasts and run dry on the western coasts and interiors.