陕西省单站暴雨特征及评估方法

Characteristic analyses and procedure evaluation of rainstorm in Shaanxi Province

基于陕西省78个气象站1961-2012年日降水资料，利用线性倾向率、Mann—Kendall检验、功率谱等统计诊断方法，对暴雨的时空分布规律和气候变化特征进行了分析；为加强暴雨事件的快速评估，建立了陕西单站单日暴雨评估方法及单站暴雨过程的综合评估指数，对2011-2012年的暴雨过程进行了试评估。结果表明：陕西暴雨主要集中在7～9月，陕南、关中西部、陕北延安及榆林东部为暴雨频次和强度大值区，此外关中北部铜川和渭南北部暴雨频次也较大；近年来关中地区和陕南中东部地区暴雨频次增加，暴雨频次的长期变化在陕北具有2a和6a的准周期，关中具有2～4a的准周期，陕南具有2—3a的准周期，暴雨强度在全省均呈增加趋势；采用等级评估、序位评估方法对单站单日暴雨进行暴雨等级评估，建立反映单站暴雨过程的综合评估指数对暴雨过程进行评估，所用方法和建立指标实用可行，能够对暴雨事件等级进行准确评估，满足科学、快速、及时评估暴雨事件的服务需求。

Applying the observation data of daily precipitation from 78 weather stations during the years of 1961- 2012, the spatial-temporal distributions and climatic characteristics of the rainstorms in Shaanxi Province are ana- lyzed by the linear trend analyses, the Mann-Kendall analyses and the power spectrum methods. To conduct the in-time evaluation on the rainstorm events, the assessment method for the daily rainstorm events for each station and the synthesized index for each procedure are established, based on this, the rainstorm procedures in 2011-2012 are further tried to be assessed. The results show that the rainstorms are primarily concentrated in the July-August-Sep- tember, which accounts for about 79% of the total year in frequency. Over Shaanbei and Guanzhong, a single peak is found respectively in July and August in the frequencies while in Shaannan it shows two peaks in July and late-Au- gust-early-September. The regions with maximal frequencies and intensities are the Shaannan, the western Guan- zhong, and the eastern Shaanbei, respectively. The rainstorm frequencies are 1-5 d/a in Shaannan and 0.7-1 d/a in the western Guanzhong and the eastern Shaanbei. And the intensity usually reaches approximately 67-80 mrn/d. In recent years, the rainstorm frequencies are significantly increased, by a rate of 5.4 times/a in Shaanxi, especially over Guanzhong and the central-eastern part of Shaannan. The frequencies have quasi-periods of 2 and 6 a in Shaanbei, 2-4 a in Guanzhong, and 2-3 a in Shaannan, respectively. The intensities of rainstorm are enhanced over the whole province with the most remarkable regions of western Guanzhong and eastern Shaanbei. In particular, the rainstorm intensity in Guanzhong emerges a abrupt change around 1985. For the rainstorm evaluation, the daily rainstorms and the procedures for each station are spectively. The method by ranking both classified into 4 levels by the frequencies of 50%, 30%, 15% and 5%, re- and ordering and procedure index are feasible and practical, satisfying the re- quirement of the in-time evaluation services for rainstorm events.