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Geography - Notes of Climate Classification for UPSC Examinations


SSBInsights Team
10 Nov 2017
exams

Climate Classification

The Köppen Climate Classification System is the most widely used system for classifying the world's climates. Its categories are based on the annual and monthly averages of temperature and precipitation. The Köppen system recognizes five major climatic types. 

Tropical rainforest climate has no dry season – all years have an average precipitation values of at least 250cm. Tropical rainforest climates have no pronounced summer or winter; it is typically hot and wet throughout the year and rainfall is both heavy and frequent. One day in an equatorial climate can be very similar to the next, while the change in temperature between day and night may be larger than the average change in temperature along the year. A tropical rainforest climate is usually found at latitudes within five degrees North and south of the equator, which are dominated by the Intertropical Convergence Zone. In some eastern-coast areas, they may extend to as much as 25° away from the equator. The climate is most commonly found in Southeast Asia, Central Africa and South America.

 

Tropical monsoon climate, occasionally also known as a tropical wet climate is a relatively rare type of climate This type of climate results from the monsoon winds which change direction according to the seasons. These climates have monthly mean temperatures above 18°C in every month of the year and feature wet and dry seasons. The tropical monsoon climate experiences abundant rainfall like that of the tropical rain forest climate, but it is concentrated in the high-sun season. This climate has driest months with less than 60 mm of precipitation (which nearly always occurs at or soon after the "winter" solstice for that side of the equator) Tropical monsoon climates are most commonly found in South Asia, Southeast Asia, Africa (particularly West and Central Africa), the Caribbean.

 

 The tropical wet and dry or savanna has an extended dry season during winter. Precipitation during the wet season is usually less than 1000 millimeters. A seasonal change occurs between wet tropical air masses and dry tropical air masses. As a result, there is a very wet season and a very dry season. Trade winds dominate during the dry season. It gets a little cooler during this dry season but will become very hot just before the wet season. Very prominent difference of Savanna climate from Tropical Monsoon Climate is that tropical monsoon climate has less variance in temperatures during the course of the year than a tropical savanna climate. Global Range: West Africa, southern Africa, South America and the north coast of Australia.

Dry Climates The most obvious climatic feature of this climate is that potential evaporation exceeds precipitation. These climates extend from 20 - 35° North and South of the equator and in large continental regions of the mid-latitudes often surrounded by mountains. Minor types of this climate include:

Dry arid (desert) is a true desert climate. It covers 12 % of the Earth's land surface. These latitude belts are centered on sub tropical high pressure belt, also called as horse latitudes.  Winds are light, which allows for the evaporation of moisture in the intense heat. They generally flow downward so the area is seldom penetrated by air masses that produce rain. This makes for a very dry. Global Range: southwestern United States and northern Mexico; Argentina; North Africa; South Africa; central part of Australia.

Dry semiarid (steppe) is a grassland climate that covers 14% of the Earth's land surface. It receives more precipitation than the Dry arid. It can be found between the desert climate and more humid climates. If it received less rain, the steppe would be classified as an arid desert. With more rain, it would be classified as a tall grass prairie (An extensive area of flat or rolling, predominantly treeless grassland, especially the large tract or plain of central North America).  The majority of the plants are xerophytic. This is characterised by small, spindly leaves, with waxy layers to reduce evaporation. Trees have gnarled trunks to reduce water loss. Extremes can be recorded in the summer of up to 40 °C and in winter, –40 °C. Besides this huge difference between summer and winter, the differences between day and night are also very great. In the highlands of Mongolia, 30 °C (86 °F) can be reached during the day with sub-zero °C (sub 32 °F) readings at night. Global Range: Western North America (Great Basin, Columbia Plateau, Great Plains); Eurasian interior, from steppes of Eastern Europe to the Gobi Desert and North China.

Since both the above climates are obtained in the interiors of the continents, they are also known as Dry mid-latitude Climates.

Moist Subtropical Mid-Latitude Climates This climate generally has warm and humid summers with mild winters. Its extent is from 30 to 50° of latitude mainly on western borders of most continents. Therefore this climate is also referred to as Oceanic climate or Marine west coast climate.  During the winter, the main weather feature is the mid-latitude cyclone. Convective thunderstorms dominate summer months. Minor groups are:

Humid subtropical climate has coldest month's mean temperature to be between -3 °C and 18 °C, and the warmest month to be above 22 °C It is either accompanied with a dry winter or has no distinguished dry season. Winter rainfall (and sometimes snowfall) is associated with large storms that the westerlies steer from west to east. Most summer rainfall occurs during thunderstorms and an occasional tropical storm, hurricane or cyclone. These climates normally lie on the southeast side of all continents, generally between latitudes 25° and 40° north and tend to be located at coastal or near coastal locations. However in some cases the climate extends well inland, most notably in China and the United States.

 A Mediterranean climate is a climate that resembles those of the lands bordering the Sea. This climate is characterized by warm to hot, dry summers and mild to cool, wet winters. These regions receive rain primarily during winter season from the mid-latitude cyclone. Extreme summer aridity is caused by the sinking air of the subtropical highs and may exist for up to 5 months. Areas with this climate receive almost all of their precipitation during their winter, autumn and spring seasons, and may go anywhere from 4 to 6 months during the summer without having any significant precipitation. Fires occur frequently in due to dry weather in summers. Most of the region being closer to large water bodies, temperature range is moderate. Global Position: central and southern California; coastal zones bordering the Mediterranean Sea; coastal Western Australia and South Australia; Chilean coast; Cape Town region of South Africa.

Moist Continental Mid-latitude Climates Moist continental mid-latitude climates have warm to cool summers and cold winters. The location of these climates is pole ward of the moist subtropical climates. The average temperature of the warmest month is greater than 10° Celsius, while the coldest month is less than -3° Celsius. Winters are severe with snowstorms, strong winds, and bitter cold from Continental Polar or Arctic air masses. Global Position: eastern parts of the United States and southern Canada; northern China; Korea; Japan; central and eastern Europe.

Polar Climates Polar and arctic air masses dominate these regions. Canada and Siberia are two air-mass sources, which fall into this group. A southern hemisphere counterpart to these continental centers does not exist. Polar climates have year-round cold temperatures with the warmest month less than 10° Celsius. Polar climates are found on the northern coastal areas of North America, Europe, Asia, and on the landmasses of Greenland and Antarctica. Two minor climate types exist.

 Polar tundra is a climate where the soil is permanently frozen to depths of hundreds of meters, a condition known as permafrost. Mosses, lichens, dwarf trees and scattered woody shrubs, dominate vegetation. The winter season is long and severe. A short, mild season exists, but not a true summer season. Global Position: arctic zone of North America; Hudson Bay region; Greenland coast; northern Siberia bordering the Arctic Ocean.

Polar ice caps have a surface that is permanently covered with snow and ice.

Global warming has more damaging effects. Increasing global temperatures are causing a broad range of changes. Sea levels are rising due to thermal expansion of the ocean, in addition to melting of land ice. Amounts and patterns of precipitation are changing. The total annual power of hurricanes has already increased markedly since 1975 because their average intensity and average duration have increased (in addition, there has been a high correlation of hurricane power with tropical sea-surface temperature).

Changes in temperature and precipitation patterns increase the frequency, duration, and intensity of other extreme weather events, such as floods, droughts, heat waves, and tornadoes. Other effects of global warming include higher or lower agricultural yields, further glacial retreat, reduced summer stream flows, species extinctions. As a further effect of global warming, diseases like malaria are returning into areas where they have been extinguished earlier.

Africa is the continent that will suffer most under climate change. Temperature rise will trigger "sharp declines in crop yield in tropical regions", estimated at 5 to 10 % in Africa with an associated increase in undernourishment, malnutrition, malaria and related deaths. Globally, Africa and Western Asia will suffer the largest crop losses, while these regions are highly dependent on agriculture and have the largest limits in purchasing power. Conflict and violence triggered by scarce resources and famine will likely bring West Africa to socio-political instability.

But there are certain benefits of Global warming as well

In Greenland, where the ice is melting, fishermen are thrilled by the return of cod and farmers are reporting higher yields. 
Higher yields of soybeans on farms in Argentina are reported. Many researchers say if the world warms up, the sweet spots for growing crops will migrate toward the poles. 
The gross domestic product of Russia and much of northern Europe would likely increase along with temperatures.

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