Physical Geography and Climatic Characteristics of TopographicCloud Experiment Area in Qilian Mountain
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Abstract:
The temporal and spatial variation of summer precipitation and the daily variation of clouds and wind direction are analyzed with the 50year climate data from the topographiccloud experiment area in Qilian Mountain. The result shows that the precipitation in the experiment area increased from north to south with increasing altitude. The observed maximum annual precipitation is 511 mm, occuring in Wafangcheng at 2500 m (ASL). The amount of precipitation in July is the biggest, while that from June to August is about 57% of annual precipitation. There is obvious daily variation in wind direction in summer, with mountainvalley circulations dominating. The most frequent wind direction is northwest in daytime and south to southeast in nighttime. Valley winds after noon make vapor converged in the hillside of Qilian Mountain to produce ascending airflow, further convective clouds. As the result, the precipitation frequency is the highest, and two precipitation peaks appear in midnight and noon, respectively, corresponding to daily variations of low cloud, cumulus and cumulonimbus amounts. The climate change of 50 years shows that annual precipitation has an increasing trend; there were two wet periods and two dry periods from 1957 to 2004; it has been in wet periods from 1998 till now. The analyses of annual precipitation and the biggest entropy spectra of annual runoff show that there are obvious periods of 4.8 years and 3 years, and the annual precipitation at Minle has a good relationship with entropy spectra.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.