Climate and the Rest of Us

Climate (from Ancient Greek klima, meaning inclination) is commonly defined as the weather averaged over a long period. The standard averaging period is 30 years, but other periods may be used depending on the purpose. Climate also includes statistics other than the average, such as the magnitudes of day-to-day or year-to-year variations. The Intergovernmental Panel on Climate Change (IPCC) glossary definition is: Climate in a narrow sense is usually defined as the "average weather," or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period ranging from months to thousands or millions of years. The classical period is 30 years, as defined by the World Meteorological Organization (WMO). These quantities are most often surface variables such as temperature, precipitation, and wind. Climate in a wider sense is the state, including a statistical description, of the climate system. The difference between climate and weather is usefully summarized by the popular phrase "Climate is what you expect, weather is what you get." Over historical time spans there are a number of nearly constant variables that determine climate, including latitude, altitude, proportion of land to water, and proximity to oceans and mountains. These change only over periods of millions of years due to processes such as plate tectonics. Other climate determinants are more dynamic: the thermohaline circulation of the ocean leads to a 5 °C (9 °F) warming of the northern Atlantic Ocean compared to other ocean basins. Other ocean currents redistribute heat between land and water on a more regional scale. The density and type of vegetation coverage affects solar heat absorption, water retention, and rainfall on a regional level. Alterations in the quantity of atmospheric greenhouse gases determines the amount of solar energy retained by the planet, leading to global warming or global cooling. The variables which determine climate are numerous and the interactions complex, but there is general agreement that the broad outlines are understood, at least insofar as the determinants of historical climate change are concerned. TYPES OF CLIMATE Tropical Climate These climates are the ones where the mean monthly temperature remains generally above 22 deg. C. and they occur in the tropical zone. They do not have a perceptible winter season. The major sub types of this type are the tropical rain-forest, tropical monsoon and the tropical savanna climates. The rain-forest climates are characterized by all the year round precipitation and they support dense evergreen forests of tall trees. The basis of the dense and tall forests is the high temperature and a large amount of precipitation, generally over 250 cms. The climates of the equatorial regions such as Zaire Basin and Amazon are of this type. In the monsoon type of tropical climates the rainfall is seasonal and generally it occurs in the summer season. Due to this the vegetation in these regions is of deciduous type, i.e. the trees shed their leaves during the dry season. India and her neighbors in the southeast Asia constitute a major area of this type of climate. The tropical savanna climate is the one in which the total amount of rainfall is lesser unlike the former two types where it is generally more than 200 cm. Due to lack of rainfall the typical type of vegetation in these regions is the open thorn type of forests and grasslands with occasional clumps of trees. Savanna type of climate is transitional between the tropical wet climates towards the equator and the dry climates towards the poles. Parts of northern Australia, Veld region of Africa and Venezuela are among the typical areas of this type. Dry Climate This climate is characterized by a general situation of water deficit and generally no permanent streams originate from such regions. It has two major sub types, tropical and subtropical deserts and the tropical and subtropical steppes. The typical areas of desert type of climate are the Sahara, Atacama, Thar, Gobi, Arabian and Kalahari deserts. This type of climate covers a vast area in Australia also. Most of the tropical deserts occupy western margins of the continents near the tropics and the subtropical deserts are usually in the interiors of the continents where the moisture bearing winds fail to reach. Due to a lack of rainfall the deserts have very limited plant and animal life. Thorny bushes and patches of grass are the typical vegetation of these regions. The tropical deserts are also called the hot deserts. The steppes are the areas of comparatively lower temperature and slightly more precipitation and the temperate grasses are the chief vegetation of these regions. They occupy poleward margins of the tropical and subtropical deserts. Much of the precipitation of these regions is provided by the cyclonic storms. American Prairies and Eurasian Steppes are the major areas of these grasslands. These regions are ideally suited for the cultivation of grain crops such as wheat. Polar Climate This climate is also known as the tundra type of climate and it is experienced in the polar regions. This climate is characterized by a long season of severe winter and even the summer season is cold. The precipitation is very low, generally below 30 cm. and due to low temperatures the vegetation is practically missing. Only during the short summer season some very lowly plants may grow only in the areas away from the polar ice caps. These regions are known for blizzards, high velocity winds carrying ice particles with them. These regions are called the cold deserts and they occupy areas of the Arctic margins of North America and Eurasia and the Antarctic continent. The Highlands Climate This type of climate is experienced in the mountainous regions such as the Himalayas, Tibetan Plateau, Rockies, Andes and the Alps. The climate of such regions is significantly modified by the altitude and the aspect of the slope and these regions have a variable climate. The temperature conditions vary according to altitude and the precipitation varies according to the aspect of the slope. Vegetation also has a vertical zonation. Generally such regions also suffer from a high diurnal range of temperature. 1. Polar o Polar climates are very cold and dry throughout the year. They encompass the South Pole, the extreme northern latitudes and the interior of Greenland. Plant life is non-existent except for some algae, while the few animal species include polar bears, killer whales, seals and penguins. Temperate o The temperate region experiences cold winters and mild summers, and covers much of North America, Europe and the northern parts of Asia. Temperate forests grow in soil fertilized by leaf litter, producing a rich diversity of plants like oak, maple, elm and willow, and animals like deer, bear, rabbits, squirrels and birds. Temperate grasslands are dominated by flowering grasses, and are populated by such fauna as lions, wolves, zebras, foxes, snakes and deer. Arid o Arid zones are hot and dry all year and include the deserts of North Africa and central Asia, the southwest United States, and inland Australia. The coarse soil contains little surface water and supports mostly shrubs and short, woody trees. Animal life includes birds, reptiles, insects, rodents and small carnivores. Tropical o The tropical region is hot and wet, covering the jungles of South America and Africa, Southeast Asia and the islands of the Pacific. This area contains the greatest diversity of plant and animal life. Tropical forests experience about 12 hours of daylight daily, with only a rainy and dry season. They can contain 100 different tree species in a half-mile square, with small fauna like birds, bats, insects and small mammals. Mediterranean o A Mediterranean climate shows mild winters and hot, dry summers, and includes the land surrounding the Mediterranean Sea, Southern South America and Southern California. Plants are typically shrubby and less than three feet tall, populated by small, nocturnal animals like geckos, snakes and rodents, which are hunted by raptors like hawks. Tundra o The tundra is very cold all year and covers the tops of mountains, the northern extremes of North America and Asia, and the southern coast of Greenland. Though plant life may be numerous, it grows low to the ground and includes grasses and shrubs. Animal populations, which expand and shrink radically depending on the season, include caribou, squirrels, foxes, wolves, bears, and migratory birds. Some facts about climate The sun's rays hit the equator at a direct angle between 23 ° N and 23 ° S latitude. Radiation that reaches the atmosphere here is at its most intense. In all other cases, the rays arrive at an angle to the surface and are less intense. The closer a place is to the poles, the smaller the angle and therefore the less intense the radiation. Our climate system is based on the location of these hot and cold air-mass regions and the atmospheric circulation created by trade winds and westerlies. Trade winds north of the equator blow from the northeast. South of the equator, they blow from the southeast. The trade winds of the two hemispheres meet near the equator, causing the air to rise. As the rising air cools, clouds and rain develop. The resulting bands of cloudy and rainy weather near the equator create tropical conditions. Westerlies blow from the southwest on the Northern Hemisphere and from the northwest in the Southern Hemisphere. Westerlies steer storms from west to east across middle latitudes. Both westerlies and trade winds blow away from the 30 ° latitude belt. Over large areas centered at 30 ° latitude, surface winds are light. Air slowly descends to replace the air that blows away. Any moisture the air contains evaporates in the intense heat. The tropical deserts, such as the Sahara of Africa and the Sonoran of Mexico, exist under these regions. Seasons The Earth rotates about its axis, which is tilted at 23.5 degrees. This tilt and the sun's radiation result in the Earth's seasons. The sun emits rays that hit the earth's surface at different angles. These rays transmit the highest level of energy when they strike the earth at a right angle (90 °). Temperatures in these areas tend to be the hottest places on earth. Other locations, where the sun's rays hit at lesser angles, tend to be cooler. As the Earth rotates on it's tilted axis around the sun, different parts of the Earth receive higher and lower levels of radiant energy. This creates the seasons. ________________________________________ Köppen Climate Classification System The Köppen Climate Classification System is the most widely used for classifying the world's climates. Most classification systems used today are based on the one introduced in 1900 by the Russian-German climatologist Wladimir Köppen. Köppen divided the Earth's surface into climatic regions that generally coincided with world patterns of vegetation and soils. The Köppen system recognizes five major climate types based on the annual and monthly averages of temperature and precipitation. Each type is designated by a capital letter. A - Moist Tropical Climates are known for their high temperatures year round and for their large amount of year round rain. B - Dry Climates are characterized by little rain and a huge daily temperature range. Two subgroups, S - semiarid or steppe, and W - arid or desert, are used with the B climates. C - In Humid Middle Latitude Climates land/water differences play a large part. These climates have warm,dry summers and cool, wet winters. D - Continental Climates can be found in the interior regions of large land masses. Total precipitation is not very high and seasonal temperatures vary widely. E - Cold Climates describe this climate type perfectly. These climates are part of areas where permanent ice and tundra are always present. Only about four months of the year have above freezing temperatures. Further subgroups are designated by a second, lower case letter which distinguish specific seasonal characteristics of temperature and precipitation. f - Moist with adequate precipitation in all months and no dry season. This letter usually accompanies the A, C, and D climates. m - Rainforest climate in spite of short, dry season in monsoon type cycle. This letter only applies to A climates. s - There is a dry season in the summer of the respective hemisphere (high-sun season). w - There is a dry season in the winter of the respective hemisphere (low-sun season). To further denote variations in climate, a third letter was added to the code. a - Hot summers where the warmest month is over 22°C (72°F). These can be found in C and D climates. b - Warm summer with the warmest month below 22°C (72°F). These can also be found in C and D climates. c - Cool, short summers with less than four months over 10°C (50°F) in the C and D climates. d - Very cold winters with the coldest month below -38°C (-36°F) in the D climate only. h - Dry-hot with a mean annual temperature over 18°C (64°F) in B climates only. k - Dry-cold with a mean annual temperature under 18°C (64°F) in B climates only. Three basic climate groups. Three major climate groups show the dominance of special combinations of air-mass source regions. Group I Low-latitude Climates: These climates are controlled by equatorial a tropical air masses. ________________________________________ • Tropical Moist Climates (Af) rainforest Rainfall is heavy in all months. The total annual rainfall is often more than 250 cm. (100 in.). There are seasonal differences in monthly rainfall but temperatures of 27°C (80°F) mostly stay the same. Humidity is between 77 and 88%. High surface heat and humidity cause cumulus clouds to form early in the afternoons almost every day. The climate on eastern sides of continents are influenced by maritime tropical air masses. These air masses flow out from the moist western sides of oceanic high-pressure cells, and bring lots of summer rainfall. The summers are warm and very humid. It also rains a lot in the winter o Average temperature: 18 °C (°F) o Annual Precipitation: 262 cm. (103 in.) o Latitude Range: 10° S to 25 ° N o Global Position: Amazon Basin; Congo Basin of equatorial Africa; East Indies, from Sumatra to New Guinea. • Wet-Dry Tropical Climates (Aw) savanna 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. o Temperature Range: 16 °C o Annual Precipitation: 0.25 cm. (0.1 in.). All months less than 0.25 cm. (0.1 in.) o Latitude Range: 15 ° to 25 ° N and S o Global Range: India, Indochina, West Africa, southern Africa, South America and the north coast of Australia • Dry Tropical Climate (BW) desert biome These desert climates are found in low-latitude deserts approximately between 18° to 28° in both hemispheres. these latitude belts are centered on the tropics of Cancer and Capricorn, which lie just north and south of the equator. They coincide with the edge of the equatorial subtropical high pressure belt and trade winds. 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 heat. The dry arid desert is a true desert climate, and covers 12 % of the Earth's land surface. o Temperature Range: 16° C o Annual Precipitation: 0.25 cm (0.1 in). All months less than 0.25 cm (0.1 in). o Latitude Range: 15° - 25° N and S. o Global Range: southwestern United States and northern Mexico; Argentina; north Africa; south Africa; central part of Australia. Group II • Mid-latitude Climates: Climates in this zone are affected by two different air-masses. The tropical air-masses are moving towards the poles and the polar air-masses are moving towards the equator. These two air masses are in constant conflict. Either air mass may dominate the area, but neither has exclusive control. • Dry Midlatitude Climates (BS) steppe Characterized by grasslands, this is a semiarid climate. It can be found between the desert climate (BW) and more humid climates of the A, C, and D groups. If it received less rain, the steppe would be classified as an arid desert. With more rain, it would be classified as a tallgrass prairie. This dry climate exists in the interior regions of the North American and Eurasian continents. Moist ocean air masses are blocked by mountain ranges to the west and south. These mountain ranges also trap polar air in winter, making winters very cold. Summers are warm to hot. o Temperature Range: 24° C (43° F). o Annual Precipitation: less than 10 cm (4 in) in the driest regions to 50 cm (20 in) in the moister steppes. o Latitude Range: 35° - 55° N. o 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. • Mediterranean Climate (Cs) chaparral biome This is a wet-winter, dry-summer climate. Extremely dry summers are caused by the sinking air of the subtropical highs and may last for up to five months. Plants have adapted to the extreme difference in rainfall and temperature between winter and summer seasons. Sclerophyll plants range in formations from forests, to woodland, and scrub. Eucalyptus forests cover most of the chaparral biome in Australia. Fires occur frequently in Mediterranean climate zones. o Temperature Range: 7 °C (12 °F) o Annual Precipitation: 42 cm (17 in). o Latitude Range: 30° - 50° N and S o 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. • Dry Midlatitude Climates (Bs) grasslands biome These dry climates are limited to the interiors of North America and Eurasia. Ocean air masses are blocked by mountain ranges to the west and south. This allows polar air masses to dominate in winter months. In the summer, a local continental air mass is dominant. A small amount of rain falls during this season. Annual temperatures range widely. Summers are warm to hot, but winters are cold. o Temperature Range: 31 °C (56°F). o Annual Precipitation: 81 cm. (32 in.). o Latitude Range: 30° - 55° N and S o Global Position: western North America (Great Basin, Columbia Plateau, Great Plains); Eurasian interior. • Moist Continental Climate (Cf) Deciduous Forest biome This climate is in the polar front zone - the battleground of polar and tropical air masses. Seasonal changes between summer and winter are very large. Daily temperatures also change often. Abundant precipitation falls throughout the year. It is increased in the summer season by invading tropical air masses. Cold winters are caused by polar and arctic masses moving south. o Temperature Range: 31 °C (56 ° F) o Average Annual Precipitation: 81 cm (32 in). o Latitude Range: 30° - 55° N and S (Europe: 45° - 60° N). o Global Position: eastern parts of the United States and southern Canada; northern China; Korea; Japan; central and eastern Europe. ________________________________________ Group III • High-latitude 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. Air masses of arctic origin meet polar continental air masses along the 60th and 70th parallels. • Boreal forest Climate ( Dfc) taiga biome This is a continental climate with long, very cold winters, and short, cool summers. This climate is found in the polar air mass region. Very cold air masses from the arctic often move in. The temperature range is larger than any other climate. Precipitation increases during summer months, although annual precipitation is still small. Much of the boreal forest climate is considered humid. However, large areas in western Canada and Siberia receive very little precipitation and fall into the subhumid or semiarid climate type. o Temperature Range: 41 °C (74 °F), lows; -25 °C (-14 °F), highs; 16 °C (60 °F). o Average Annual Precipitation: 31 cm (12 in). o Latitude Range: 50° - 70° N and S. o Global Position: central and western Alaska; Canada, from the Yukon Territory to Labrador; Eurasia, from northern Europe across all of Siberia to the Pacific Ocean. • Tundra Climate (E) tundra biome The tundra climate is found along arctic coastal areas. Polar and arctic air masses dominate the tundra climate. The winter season is long and severe. A short, mild season exists, but not a true summer season. Moderating ocean winds keep the temperatures from being as severe as interior regions. o Temperature Range: -22 °C to 6 °C (-10 °F to 41 °F). o Average Annual Precipitation: 20 cm (8 in). o Latitude Range: 60° - 75° N. o Global Position: arctic zone of North America; Hudson Bay region; Greenland coast; northern Siberia bordering the Arctic Ocean. ________________________________________ • Highland Climate (H) Alpine Biome Highland climates are cool to cold, found in mountains and high plateaus. Climates change rapidly on mountains, becoming colder the higher the altitude gets. The climate of a highland area is closely related to the climate of the surrounding biome. The highlands have the same seasons and wet and dry periods as the biome they are in. Mountain climates are very important to midlatitude biomes. They work as water storage areas. Snow is kept back until spring and summer when it is released slowly as water through melting. o Temperature Range: -18 °C to 10 °C (-2 °F to 50°F) o Average Annual Precipitation: 23 cm (9 in.) o Latitude Range: found all over the world o Global Position: Rocky Mountain Range in North America, the Andean mountain range in South America, the Alps in Europe, Mt. Kilimanjaro in Africa, the Himalayans in Tibet, Mt. Fuji in Japan. THE LOCATION OF THE ABOVE TYPES OF CLIMATE Worldwide Climate Classifications References 1. ^ AR4 SYR Synthesis Report Annexes. Ipcc.ch. Retrieved on 2011-06-28. 2. ^ C. W. Thornthwaite (1948). "An Approach Toward a Rational Classification of Climate". Geographical Review 38 (1): 55–94. doi:10.2307/210739. JSTOR 210739. 3. ^ "Climate". Glossary of Meteorology. American Meteorological Society. Retrieved 2008-05-14. 4. ^ "Climate averages". Met Office. Retrieved 2008-05-17. 5. ^ Intergovernmental Panel on Climate Change. Appendix I: Glossary. Retrieved on 2007-06-01. 6. ^ National Weather Service Office Tucson, Arizona. Main page. Retrieved on 2007-06-01. 7. ^ Stefan Rahmstorf The Thermohaline Ocean Circulation: A Brief Fact Sheet. Retrieved on 2008-05-02. 8. ^ Gertjan de Werk and Karel Mulder. Heat Absorption Cooling For Sustainable Air Conditioning of Households. Retrieved on 2008-05-02. 9. ^ Ledley, T.S.; Sundquist, E. T.; Schwartz, S. E.; Hall, D. K.; Fellows, J. D.; Killeen, T. L. (1999). "Climate change and greenhouse gases". EOS 80 (39): 453. Bibcode:1999EOSTr..80Q.453L. doi:10.1029/99EO00325. Retrieved 2008-05-17. 10. ^ United States National Arboretum. USDA Plant Hardiness Zone Map. Retrieved on 2008-03-09