Diurnal Variations of Summer Precipitation in Xinjiang
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Abstract
Fundamental diurnal variation features of summer precipitation over Xinjiang are investigated based on hourly precipitation data of 1991-2014 from all 16 national stations in the target region, and distinct characteristics on the diversity of diurnal variations of summer precipitation between Northern and Southern Xinjiang are revealed. Results show that the diurnal variation of the precipitation amount in Northern Xinjiang presents nearly a single peak and trough, with the maximum at dusk (1600-2000 LST) and minimum about one-third proportion of peak value at noon time, and the precipitation amount almost decrease monotonically during the whole night. Differently, the diurnal variation of the precipitation amount in Southern Xinjiang shows triple peaks and troughs, with peaks at about dusk (1700-1800 LST), after the midnight (0000-0100 LST) and near the noon (1000 LST), respectively. The difference of single peak pattern between Northern Xinjiang and central-east China is the accumulation of different situations instead of similar peak overlay. In addition, the morning when precipitation peak value appears in Southern Xinjiang is opposite to that weaker or weakest time in all day in central-east China.The occurrence time of maximum average precipitation intensity and maximum hourly accumulative precipitation is more consistent with the counterpart of maximum hourly accumulative precipitation frequency, and more remarkable with the region where daily variation of precipitation presents multi-peak patterns, showing more contribution of precipitation intensity than frequency to accumulative precipitation, which is also an important characteristic of Xinjiang, especially in Southern Xinjiang. Short-duration precipitation within 6 hours are dominated events in summer (the average value is 85 percent which is significantly higher than that in central-east China), and precipitation events lasting longer than 12 hours happen rarely. Contribution rates of short-duration precipitation events within 6 hours in total precipitation are up to 54% which is higher than that in central-east China in most region except the east side of Tianshan in Xinjiang.Except in the south edge of Tarim Basin, there are close relations between the precipitation diurnal cycle and its duration in most areas of Xinjiang, but not the same as those in central-east China. Namely, 2-3-hour short-duration precipitation events contribute to the peak value of the total precipitation diurnal cycle in western and Northern Xinjiang, whereas every duration event within 12 hours has nearly equal contribution to the maximum of the total precipitation diurnal cycle in central to eastern Tianshan Mountains.
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