Intra-seasonal Inhomogeneity of Summer Extreme Precipitation in the East Part of Northwest China

Based on 33 weather stations daily precipitation datasets in the east of Northwest China from 1960 to 2004, the extreme precipitation threshold of different stations are defined by centesimal value method, by introducing extreme precipitation concentration degree and period which reflects time distribution feature. Intra-seasonal inhomogeneity characteristics of extreme precipitation are analyzed by the new parameter in the east of Northwest China. The result show that the summer extreme precipitation shows increasing trend in the east of Northwest China. From long term tendency, it is found that the summer extreme precipitation displays clear inter-annual variability since 1980s. Moreover, it shows distinct inter-decadal change in the recent 45 years. It is proved that inconspicuous spatial difference is reflected by extreme precipitation concentration degree and period. It is also found that there is high relativity between summer extreme precipitation concentration degree and concentration period and summer extreme precipitation in the east of Northwest China. If the summer extreme precipitation concentration degree leans to high and concentration period leans to early date, the extreme precipitation leans to more amount, vice versa. It is proved that summer extreme precipitation concentration degree and period exhibit remarkable inter-decadal period vibration in recent 45 years. Despite summer total precipitation showing decreasing trend in the east of Northwest China, the summer extreme precipitation displays increasing trend, therefore it shows that there exist negative correlation between summer extreme precipitation, summer extreme precipitation concentration period and east Asian summer monsoon, but there is positive correlation between summer extreme precipitation concentration degree and east Asian summer monsoon, moreover its relativity is more remarkable between extreme precipitation.