Test: Climatology - 4 - UPSC MCQ

• When the wind blows moist air over a cool surface, the air will cool, and advection fog will form. Advection fog is widespread at sea when tropical winds pass over cooler waters and on land when a warm front passes over heavy snow.

• Sea fog forms when the condensation nucleus is salt. Salt is, of course, prevalent near the ocean where it is kicked up into the atmosphere by the breaking waves.

• An anticyclone - also known as a high-pressure area - is a large atmospheric circulation system with the wind flowing clockwise around it in the Northern Hemisphere, and counterclockwise in the Southern Hemisphere.

• The extents are generally large, and the effects are also pronounced.

• Anticyclones form from air masses cooling more than their surroundings, which causes the air to contract slightly, making the air denser. Since dense air weighs more, the weight of the atmosphere overlying a location increases, causing increased surface air pressure. Winds are of moderate speed, and at the outer edges, cloudy and precipitation conditions exist. Cloudy conditions and precipitation exist at the periphery of anticyclones. Otherwise, such a high-pressure region generally shows fine and clear weather.

• Extratropical storms are a global, rather than a localised, phenomena with moisture usually carried in the upper atmosphere (unlike tropical storms where it is carried in the lower atmosphere). In the case of the subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas.

• Jet streams are an important component of upper air circulation which is dominated by the westerly flow. These jet streams blow south of Himalayas, all through the year except in summer affecting India's climate and weather.

• The western cyclonic disturbances experienced in the north and north-western parts of the country are brought in by this westerly flow which affects rainfall in Northern and north-western India.

• The extratropical cyclones have a clear frontal system which is not present in the tropical cyclones.

• They cover a larger area and can originate over the land and sea, whereas the tropical cyclones originate only over the seas and on reaching the land they dissipate.

• The extratropical cyclone affects a much larger area as compared to the tropical cyclone.

• Moreover, the wind velocity in a tropical cyclone is much higher, and it is more destructive. The extratropical cyclones move from west to east, but tropical cyclones move from east to west. No jet streams are required for its movement, so 3 is wrong.

• In tropical regions, tropical cyclones are more common. So, (a) is less appropriate than (d).

• Mid-latitude or frontal cyclones are large travelling atmospheric cyclonic storms up to 2000 km in diameter with centres of low atmospheric pressure.

• Mid-latitude cyclones are the result of the dynamic interaction of warm tropical and cold polar air masses at the polar front.

• This interaction causes the warm air to be cyclonically lifted vertically into the atmosphere where it combines with colder upper atmosphere air. This process also helps to transport excess energy from the lower latitudes to the higher latitudes.

• Mechanism of tropical cyclones Heating of ocean water creates a low- pressure area to fill which wind from several high-pressure areas converge at high speeds.

• Due to the presence of Coriolis force, they start circulating the low-pressure zone. The evaporated moisture from the ocean's low-pressure area condenses above in the form of cumulonimbus clouds.

• This latent heat of condensation from the moisture feeds more heat to the cyclone and intensifies it. On reaching the land, the cyclone dissipates as its moisture supply is cut off.

• Extratropical cyclones Formed in mid and high latitudes, beyond the tropics Forms along polar fronts - Derives its energy from a meeting and circulation of warm and cold air front.

• Areas of sinking air which result in high pressure are called anticyclones.

• Light-pressure systems have small pressure gradients (i.e. the air pressure doesn't change rapidly). This means that the winds are gentle. As the air sinks, it warms up, leading to warm and dry weather.

• Anticyclones are much larger than depressions and produce periods of settled and calm weather lasting many days or weeks. Anticyclones often block the path of depressions, either slowing down the bad weather or forcing it around the outside of the high-pressure system. They are then called 'Blocking Highs'.

• As the air descends, air pressure increases. When air hits the ground, it has to go somewhere. The Earth's rotation makes the air change direction. In the Northern Hemisphere, the air is pushed clockwise. In the Southern Hemisphere, the air is pushed anticlockwise.

• Thunderstorms are caused by intense convection on moist hot days. A thunderstorm is a well-grown cumulonimbus cloud producing thunder and lightning. When the clouds extend to heights where sub-zero temperature prevails, hails are formed, and they come down as hailstorms. If there is insufficient moisture, a thunderstorm can generate dust storms.

• A thunderstorm is characterised by the intense updraft of rising warm air, which causes the clouds to grow bigger and rise to a greater height. This causes precipitation.

Dos and Don'ts during a Thunderstorm:

• Open vehicles, like motorbikes, tractors, construction machinery and open cars are not safe. Open fields, tall trees, shelters in parks, elevated places do not protect us from lightning strokes.

• Carrying an umbrella is not a good idea at all during thunderstorms. If in a forest, take shelter under shorter trees.

• If no shelter is available and you are in an open field, stay far away from tall trees.

• Stay away from poles or other metal objects. Do not lie on the ground. Instead, squat low on the ground. Place your hands on your knees with your head between the hands. This position will make you the smallest target to be struck.

Lightning is a very rapid and massive - discharge of electricity in the atmosphere. Some of which is directed towards the Earth's surface.

These discharges are generated in giant moisture-bearing clouds that are 10-12 km tall.

There is a greater probability of lightning. Striking tall objects such as trees, towers or buildings.
Lightning does not always strike tall object, but there is the chance that tall object may get striked by lightning. Hence 1 and 3 statement is always true but 2 is partially true. Hence correct option is C.
 

A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as twisters or cyclones, although the word cyclone is used in meteorology, in a wider sense, to name any closed low pressure circulation.

• Tropical cyclones can relieve drought conditions as they often carry moisture-laden winds. In addition to strong winds and rain, tropical cyclones are capable of generating high waves, damaging storm surge and tornadoes.

• They typically weaken rapidly over and where they are cut off from their primary energy source. For this reason, coastal regions are particularly vulnerable to damage from a tropical cyclone as compared to inland regions. Heavy rains, however, can cause significant flooding inland, and storm surges can produce extensive coastal flooding up to 25 miles from the coastline.

• Since dense air weighs more, the weight of the atmosphere overlying a location increases, causing increased surface air pressure. Winds are of moderate speed, and at the outer edges, cloudy and precipitation conditions exist. Cloudy conditions and precipitation exist at the periphery of anticyclones. Otherwise, such a high-pressure region generally shows fine and clear weather.

• They lie between 30°N and 30°S latitudes in the atmosphere, around which high-velocity winds blow. They are not found near the equator where there is no Coriolis force. It extends up to 500-1,000 km horizontally and from the surface up to 12-14 km vertically.

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  Like a heat engine, a tropical cyclone or hurricane is energised by latent heat that is released by the condensation of moisture that the wind gathers after passing oceans and seas. Large pressure gradients characterise tropical cyclones. The cyclone centre is predominantly a warm, low-pressure, cloudless core known as the eye of the storm.

• A typhoon is a mature tropical cyclone that develops between 180° and 100°E. This region is referred to as the Northwestern Pacific Basin. It is the most active tropical cyclone basin on Earth, accounting for almost one-third of the world's annual tropical cyclones.

• A typhoon differs from a cyclone or hurricane only based on location.

• A hurricane is a storm that occurs in the Atlantic Ocean and the northeastern Pacific Ocean.

• A typhoon occurs in the northwestern Pacific Ocean.

• A cyclone occurs in the south Pacific or the Indian Ocean.

Instead, they simply fill the low-pressure zone. This is the reason cyclones start forming only after some distance away from the equator.

• According to the Indian Meteorological Department, this is because, in addition to the storms that originate in the southeast Bay of Bengal and the adjoining Andaman Sea, breakaway typhoons over the Northwest Pacific move across the South China Sea into the Bay of Bengal, intensifying into cyclones.

• As the frequency of typhoons over the Northwest Pacific is about 35% of the global annual average, the Bay of Bengal is affected.

• In contrast, Arabian Sea cyclones are mostly their own formations and they also generally move north-west, away from India's west coast.

• Besides, the Arabian Sea is colder than the Bay of Bengal, which inhibits the formation and intensification of the cyclonic system in the former. Warm sea surface temperature is an ideal platform for cyclones.

• A total of 26 of 35 deadliest tropical cyclones have been witnessed in the Bay of Bengal.

• As per IMD, for the severe cyclonic storm, the speed is 89-117 km/hr. For speeds >220km/hr, it is a super cyclonic storm. The Phailin cyclone falls under the extremely severe cyclonic storm.

• Evergreen forests do not shed their leaves simultaneously in any season of the year. Deciduous forests shed their leaves in a particular season to conserve loss of moisture through transpiration.

• This is responsible for the seasonal variation, which affects the timing when trees shed their leaves. Forests are further classified as tropical or temperate based on their location in different latitudes.

• Forests found near the Equator (10° North to 10° South) in Amazon and Zaire Basin and Southeast Asia are major evergreen forests. The thick canopies of the closely spaced trees do not allow the sunlight to penetrate inside the forest even in the daytime.

• Thus, the grass is not found in these forests. Maximum varieties of trees are found. Trees are tall with large trunks. Hardwood trees like rosewood, teak, sal, ebony and mahogany are the common trees Found here.

• Here the population found is very less. Due to dense forests, commercial exploitation of these forests has not been possible, making them economically backwards.

• These are large butts on all sides of a bottom-rooted butt.

• Almost all types of mangroves have these types of roots. Most rainforest soil is impoverished with all the nutrients available largely remaining at surface level. Because of this rainforest trees have very shallow roots.

• Some very tall trees have developed ways of obtaining much needed additional support by forming buttressed roots, which grow out from the base of the trunk sometimes as high as 15 ft above the ground. These extended roots also increase the area over which nutrients can be absorbed from the soil.

• When the roots spread horizontally, they can cover a wider area for collecting nutrients. They stay near the upper soil layer because all the main nutrients are found there.

• The canopy tree species are mostly tall hardwoods with broad leaves like rosewood, ebony, mahogany.

• The hardwood trees found in these forests are sal, teak, neem and shisham.

• They comprise both hard and soft wood trees like oak, pine, eucalyptus, etc.