1959—2008年黄土高原地区年内降水集中度和集中期时空变化特征

本文基于黄土高原地区1959．2008年51个地面气象台站的逐日降水资料，计算了降水集中度（PCD）和集中期（PCP），并结合EOF、趋势分析以及相关分析等方法对我国黄土高原地区年内降水不均匀性特征及其趋势进行了分析。结果表明：①黄土高原地区PCD在0．53-0．75之间，自东南向西北逐渐增加，而PCP变化不大，主要集中在7月中旬和下旬；②近50a黄土高原地区PCD主要以南北反向型分布为主；③从变化趋势来看，PCD增加趋势较明显的区域主要分布在宁夏的同心和山西的五台山等地，PCD减小比较明显的区域主要分布在山西的阳泉以及青海的门源等地区；而PCP整体上呈现提前趋势，只有青海的门源站附近有小幅推迟趋势；④年降水量与PCD有较好的相关性，大部分地区都通过了显著水平为0．05的检验；而年降水量与PCP的相关性并不显著，通过显著水平0．05检验的区域仅分布在山西的兴县、陕西的洛川以及宁夏的固原等地。

Inhomogeneity Characteristics of Intra-annual Precipitation on the Loess Plateau During 1959-2008

This article aims to analyze the inhomogeneity characteristics of inter-annual precipitation on the Loess Plateau,and to provide reference for local vegetation construction and ecological recovery,rational use of water resources,and the prevention and control of soil and water loss.Precipitation concentration degree(PCD) and precipitation concentration period(PCP) were used to analyze the inhomogeneity characteristics of inter-annual precipitation and its trend in recent 50 years based on 51 meteorological stations of the Loess Plateau from 1959 to 2008,and EOF,correlation analysis and trend analysis were also employed.The results are shown as follows.(1) The annual precipitation of the Loess Plateau is between 50-850 mm,with a decreasing trend from southeast to northwest.(2) The PCD of the Loess Plateau region is between 0.53 and 0.75,which gradually increased from the southeast to the northwest,while the PCP is mainly observed in the mid-and late July.(3) In spatial distribution,PCD mainly manifests a north-south reverse pattern with a decreasing trend,while PCP consists of two main centers(east-west reverse and southwest and east-other areas reverse).(4) In terms of changing trend,the average trend coefficient of PCD on the Loess Plateau is 0.005,while that of PCP is-0.21.The regions with obviously increased PCD are mainly distributed in Ningxia and the Mount Wutai in Shanxi,and the areas with obviously decreased PCD include Yangquan of Shanxi and Menyuan of Qinghai,while PCP shows a decreasing trend in most parts of the Loess Plateau.(5) PCD shows a positive correlation with annual precipitation,most of which has passed the significant level 0.05,while PCP has a slight correlation with precipitation,the places that has passed the significant level 0.05 are only distributed in Xingxian of Shanxi,Luochuan of Shaanxi and Guyuan of Ningxia.