Analysis on the Characteristics of Daily Variation of Cloud and Precipitation over the Huangshui River Valley in Summer

Abstract

This paper analyzes the characteristics of daily variation of cloud and precipitation over the Huangshui River Valley in Qinghai Province in summer(from June to August) during the period from 2005 to 2007 using the data of cloud appearance,cloud amount,precipitation,wind direction and wind speed observed by Xining,Ping' an,Ledu and Minhe meteorological stations,and the effects of mountain-valley wind on orographic cloud and precipitation are analyzed based on the local circulation over the valley.The results show that the diurnal precipitation and its frequency at all levels are higher than the nocturnal ones in the Huangshui River Valley,the peak values of precipitation occur at afternoon,midnight and in early morning,and the minimum values occur around 12:00～14:00 and 18:00.The total cloud cover and low cloud amount over the Huangshui River Valley are higher at daytime than that at night.Stratocumulus occurs mostly at midnight and in early morning and increases gradually from 5:00,and convective cloud increases at afternoon.Mountain-valley wind affects precipitation in the Huangshui River Valley,and its occurring time accords with that of the peak value of convective cloud.