降水年内分配不均匀性指标

径流量及其分配过程依赖于降雨特征,它关系到水利设施规模和水资源合理配置。本文借鉴水文界经验,应用降雨集中度、降雨不均匀系数和调节系数概念,并对后2个系数进行修订,使其值域介于0～1。利用中原地区有代表性的4个气象台站1951—2005年的日降雨资料,计算并分析比较了降雨集中度、降雨不均匀系数和调节系数在河南省的适用性。结果表明:降水集中度、降水不均匀系数和调节系数从不同侧面反映了降水量的年内分布特征。3个指标具有一定的可比性,但数值上用同样资料计算的调节系数都要大于不均匀系数;4站候、旬和月的降水不均匀系数有相同的分布规律,随着时段的延长,不均匀系数增大,其变幅也增大,而调节系数则不同,随着时段的延长,降水调节系数减小,而相应的变幅则增大;分别采用候、旬和月的降水资料计算的降水集中度、不均匀系数和调节系数之间具有很好的一致性,最小的相关系数为0.60(P<0.001),说明3个指标间可互为代替;采用候、旬和月计算的降水集中度两两之间呈显著相关,相关系数为0.98;候、旬和月不均匀系数之间的相关系数为0.75;候、旬和月的调节系数之间的相关系数与不均匀系数相当。表明这3个指标在不同时间尺度间具有明显的一致性,在河南区域只应用月降水量就能反应降水的不均匀性。

Non-uniformity index of annual precipitation distribution

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.