3/04/2011

Climate of Jordan


The climate in Jordan is semi-dry in summer with average temperature in the mid 30°C (mid 90°F) and relatively cold in winter averaging around 13 °C (55 °F). The western part of the country receives greater precipitation during the winter season from November to March and snowfall in Amman (756 m (2,480 ft) ~ 1,280 m (4,199 ft) above sea-level) and Western Heights of 500 m (1,640 ft). Excluding the rift valley the rest of the country is entirely above 300 m (984 ft)(SL).[63]

The major characteristic of the climate is humid from November to March and semi dry weather for the rest of the year. With hot, dry summers and cool winters during which practically all of the precipitation occurs, the country has a Mediterranean-style climate. In general, the farther inland from the Mediterranean a given part of the country lies, the greater are the seasonal contrasts in temperature and the less rainfall. Atmospheric pressures during the summer months are relatively uniform, whereas the winter months bring a succession of marked low pressure areas and accompanying cold fronts. These cyclonic disturbances generally move eastward from over the Mediterranean Sea several times a month and result in sporadic precipitation.

Most of the land receives less than 620 mm (24.4 in) of rain a year and may be classified as a semi dry region. Where the ground rises to form the highlands east of the Jordan Valley, precipitation increases to around 300 mm (11.8 in) in the south and 500 mm (19.7 in) or more in the north. The Jordan Valley, forms a narrow climatic zone that annually receives up to 900 mm (35.4 in) of rain in the northern reaches; rain dwindles to less than 120 mm (4.7 in) at the head of the Dead Sea.

The country's long summer reaches a peak during August. January is usually the coldest month. The fairly wide ranges of temperature during a twenty-four-hour period are greatest during the summer months and have a tendency to increase with higher elevation. Daytime temperatures during the summer months frequently exceed 29 °C (84.2 °F) and average about 32 °C (89.6 °F). In contrast, the winter months—September to March—bring moderately cool and sometimes very cold weather, averaging about 3.2 °C (37.8 °F). Except in the rift depression, frost is fairly common during the winter, it may take the form of snow at the higher elevations of the north western highlands. Usually it snows a couple of times in the winter.

For a month or so before and after the summer dry season, hot, dry air from the desert, drawn by low pressure, produces strong winds from the south or southeast that sometimes reach gale force. Known in Western Asia by various names, including the khamsin, this dry, sirocco-style wind is usually accompanied by great dust clouds. Its onset is heralded by a hazy sky, a falling barometer, and a drop in relative humidity to about 10%. Within a few hours there may be a 10 °C (18.0 °F) to 15 °C (27.0 °F) rise in temperature. These windstorms ordinarily last a day or so, cause much discomfort, and destroy crops by desiccating them. The shamal, comes from the north or northwest, generally at intervals between June and September. Steady during daytime hours but becoming a breeze at night, the shamal may blow for as long as nine days out of ten and then repeat the process. It originates as a dry continental mass of polar air that is warmed as it passes over the Eurasian landmass.


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