(Discussion – Climate Part 1) Tuesday May 1, 2018 (Discussion – Climate Part 1) Part 2

Climate Classification A climate classification system brings order to large quantities of information, and many climatic-classification systems have been devised. The Köppen classification of climates is the best known and most widely used system. This system uses mean monthly and annual values of temperature and precipitation.

Climate Classification The Köppen classification of climates describes five principal climate groups: humid tropical (A) dry (B) humid middle-latitude with mild winters (C) humid middle-latitude with severe winters (D) polar (E) A, C, D, and E climates are defined on the basis of temperature characteristics. Precipitation is the primary criterion for the B group.

Climates of the World Based on the Köppen Classification Figure 20.4

Humid Tropical (A) Climates The three main types are: Köppen Climates Humid Tropical (A) Climates These are winterless climates, with all months having a mean temperature above 64ºF. The three main types are: wet tropics (Af), with high temperatures and year-round rainfall, luxuriant vegetation (tropical rain forest.) These climates exist in a discontinuous belt astride the equator, and are strongly influenced by the equatorial low pressures.

Humid Tropical (Af) Rain Forests Köppen Climates Humid Tropical (Af) Rain Forests

Humid Tropical (A) Climates The three main types are: Köppen Climates Humid Tropical (A) Climates These are winterless climates, with all months having a mean temperature above 64ºF. The three main types are: Tropical monsoon (Am), with monthly mean temperatures above 64.4°F in every month of the year and feature wet and dry seasons. Unlike tropical savanna climates, a tropical monsoon climate's driest month sees less than 60 mm of precipitation but more than (100 − [total annual precipitation {mm}/25]). Also a tropical monsoon climate tends to see less variance in temperatures during the course of the year than a tropical savanna climate. This climate has a driest month which nearly always occurs at or soon after the "winter" solstice for that side of the equator These climates exist in a discontinuous belt astride the equator, and are strongly influenced by the equatorial low pressures.

Köppen Climates Tropical Monsoon (Am)

Humid Tropical (A) Climates Köppen Climates Humid Tropical (A) Climates These are winterless climates, with all months having a mean temperature above 64ºF. The two main types are: tropical wet and dry (Aw), which are found poleward of wet tropics and equator-ward of the tropical deserts. These climates consist of tropical grassland (savanna), with seasonal rainfall.

Humid Tropical (Aw) Savannahs Köppen Climates Humid Tropical (Aw) Savannahs

Comparison of A-Type Climates Rainforest Monsoon Savannah Figure 20.6

The two main B-type climates are: Semiarid or steppe (Bs) Köppen Climates Dry (B) Climates These are climates where evaporation exceeds precipitation, and there is a constant water deficiency. The boundary of these climate zones are determined by formulas involving three variables - average annual precipitation, average annual temperature, and seasonal distribution of precipitation. The two main B-type climates are: Arid or desert (Bw) Semiarid or steppe (Bs) BS climates are more humid than arid BW climates; they surround deserts. Examples include North Africa to northwestern India, northern Mexico, and the southwestern U.S.

Arid and Semiarid Climates of the World Figure 20.8

Köppen Climates Dry (B) Climates Causes of Deserts and Steppes In the low latitudes, deserts and steppes coincide with the dry, stable, subsiding air of the subtropical high-pressure belts. In middle-latitudes, deserts and steppes are due to their position in the deep interiors of large landmasses and/or the presence of high mountains. Most of these are located in the Northern Hemisphere.

Köppen Climates Dry (Bw) Deserts

Köppen Climates Dry (Bs) Steppes

Comparison of B-Type Climates Figure 20.9