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Weather and climate

Climate types

Semi-arid climate: Tirunelveli, IndiaSemi-arid climate: Tirunelveli, IndiaClimate is the long-term pattern of weather in a particular area. It is the result of a number of factors, including that area's latitude, which affects the amount of heat it receives from the Sun, and the way that winds carry the Sun’s warmth and rain-laden clouds around the globe. Winds are themselves affected by whether the ocean currents they blow over are warm or cold, or whether a high mountain range may block their movement. It is possible to identify a number of climate types, each of which share broadly similar characteristics, that are found in different parts of the world. 

Spring blossom in TokyoSpring blossom in Tokyo

Köppen climate classification

A system of classifying climates was proposed in 1900 by Russian-German scientist Wladimir Köppen. Observing that the type of vegetation in a region was closely related to its climate, Köppen used monthly average temperature and precipitation records to produce a system for classifying climates. According to his classification system, there are five major climate groups, each identified by a letter: tropical (A), dry (B), mild (C), continental (D) and polar (E). Dry climates are subdivided according to whether they are desert climates (BW) or semi-arid steppe climates (BS). Within all the groups there are variations, which are described in detail below.

Southern California has a Mediterranean climate. During the hot summer, warm air rising inland creates a low pressure area. This draws in winds from over the Pacific Ocean through the Golden Gate near San Francisco (as well as other places along the coast), creating frequent fogs.

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