Colombia – Climate
The climate, however, varies with the elevation. The low regions along the coast and the deep Patía and Magdalena river valleys are torrid, with mean annual temperatures of 75° to 80° F. From about 1500 to 7500 ft the climate is subtropical, and from about 7500 to 10,000 ft it is temperate. Above about 10,000 ft is the cold-climate zone, where temperatures range from 0° to 55° F.
The average January and July temperatures in Bogotá are 58° F and 57° F, respectively. The averages for the same months in Barranquilla are 80° F and 82° F. Throughout the year, three-month periods of rain and dry weather alternate. Along the Pacific coast precipitation is heavy. At Bogotá the annual rainfall averages about 40 in, and in Barranquilla it averages about 32 in. Dry weather prevails on the slopes of the Eastern Cordillera.
CIRCULATION SYSTEMS OVER CHINA
The Earth's atmosphere is in continuous motion: movement which is attempting to balance the constant differences in pressure and temperature between different parts of the globe. It is this motion which carries water from the ocean to the continents to provide precipitation and moves heat energy from the tropical regions toward the poles, warming the high latitudes. It is this circulation which plays a basic part in maintaining a steady state in the atmosphere and generating the climatic zones which characterise different parts of the earth.
China, from its latitudinal location, mostly belongs to the mid-latitudes, with a small part to the low latitudes. It is located at south of Siberia and the north of the tropical Pacific. At this distinctive location, the country is affected by the alternate seasonal expansion and contraction of the polar continental highs and tropical maritime air masses, along with the seasonal shifts of the overhead sun. These changes in the pressure systems over Asia generate the unique Asian monsoon circulation which prevails over China throughout the year.
Surface Pressure Field and Winds:
For any fluid to initiate movements, pressure gradient must exists. Therefore, for a close understanding of the circulation system that operates over China, we should start from discussing the seasonal pressure distribution at sea-level over the Asia-Pacific region, which is the driving force for the air movements in China. Most clearly to be seen, the largest difference in the atmospheric pressure occurs between winter and summer, whereby January and July can be considered as representative months.
In January, a typical cold anticyclone with central pressure above 1,040 hectopascals (hPa) developed over mid-Siberia and Mongolia (Mongolian High); while a strongly established cyclone over the north-western Pacific Ocean (Aleutian Low). Since both pressure systems practically lie in the same latitude of 50° to 55°N, a steep pressure gradient occurs which produces strong and persistent north-westerlies over Northeast China.
A third pressure system which affects China, although limited only to south-eastern China, is the equatorial Low over Australia and New Guinea. The vast territory of East China lies in the middle of the path along which the Mongolian cold air tries to rush southward into the Equatorial Low. Northerly and north-easterly flows prevail over the eastern half of China.
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