Non-uniformity index of annual precipitation distribution
降水年内分配不均匀性指标

Precipitation is an important factor affecting runoff process.Based on the daily precipitation data in 1951-2005 obtained from Zhengzhou,Xinyang,Anyang and Xinxiang meteorological stations in central Henan Province,the temporal non-uniformity of annual precipitation distribution,including precipitation concentration degree,non-uniformity coefficient and regulation coefficient,were analyzed.The results showed that all the indices at each station exhibited different levels of non-uniformity.The precipitation concentration degree calculated on pentad,decade and month scales had a good consistency,and the means and standard deviations were very close.The non-uniformity coefficient was smaller than regulation coefficient,and its mean and standard deviation increased with increasing length of study period,while the mean and standard deviation of regulation coefficient decreased and increased respectively with increasing length of study period.There were significant correlations among concentration degree,non-uniformity coefficient and regulation coefficient on different time scales,and thereby,all these indices could be calculated simply on monthly scale.The correlations among precipitation degree,non-uniformity coefficient and regulation coefficient were also significant,and as a result,all the indices could be replaced each other.In Henan region,we could use the monthly precipitation alone to reflect the non-uniformity of annual precipitation distribution satisfactorily.