重庆市干旱强度时空分布规律研究

根据重庆市34个国家级气象站点1961～2016年的日降水量数据,基于重庆市干旱标准,提出重庆市季节性干旱强度指数及年干旱强度综合指数的新算法,并研究重庆市干旱强度的时空分布规律。结果表明,重庆市季节性干旱强度的区域差异大,渝东北夏旱、秋旱及冬旱严重,渝西部为春旱、夏旱的主要分布区,渝中部伏旱最严重;渝东北除春旱外的其他季节性干旱、渝东南的伏旱及秋旱、渝西的夏旱及伏旱和渝中部的伏旱,其季节性干旱强度指数极值均可达到特重旱标准。年干旱强度具有从渝西部向渝东南减小的分布规律,渝西部地区干旱强度最大,其次是渝中部地区和渝东北地区,渝东南地区干旱强度最小。重庆市季节性干旱强度的时间变化趋势不同,春旱及冬旱强度指数总体上呈减小趋势,伏旱和秋旱强度指数总体上呈增加趋势,夏旱强度指数和年干旱强度综合指数时间变化趋势的地区差异较大。近55年来重庆市年干旱强度综合指数变化具有显著的3 a、5 a和18 a的周期性变化和阶段性变化,Hurst指数预测未来短时间内年干旱强度综合指数将增强。     

基于SPEI和SPI指数的青海省东部农业区春夏气象干旱特征的评估

青海省东部农业区是青海省重要的粮食生产基地,春夏干旱直接影响着该区农业的有序发展。论文选取青海省东部农业区13个气象站点1961-2014年平均月降水和气温数据,采用泰森多边形法、SPEI和SPI指数、R/S分析等方法对比评估了该区的春夏气象干旱演变特征。研究表明：1）近54 a SPEI和SPI指数显示青海省东部农业区干旱年际变化在2000年代前基本一致,2000年代后变化趋势发生变化;SPEI指数显示2000年代后春夏旱逐渐加重,SPI指数显示2000年代后春旱逐渐缓解该区干旱,气温是导致两者产生差异的主要原因。2）该区干旱面积覆盖率与干旱年际变化规律保持一致,两种指数主要在1990年代中期前后有所不同,1990年代中期后SPEI指数显示的春夏干旱覆盖面积要比SPI指数显示的广。3）SPEI和SPI指数在2000年代后春夏干旱频率呈相反趋势,SPEI指数显示的2000年代为干旱高频期,SPI指数为干旱低频期;两种指数均显示春旱高频区由西部转向东部地区,夏旱高频区由西北转向东南地区。4）根据干旱周期及R/S分析法,未来4~6 a该区春旱加重,北部地区为春旱高发区;未来18~22 a夏旱也有所加重,西部和东部地区为夏旱高发区。5）通过对比分析发现,SPEI指数在该区的适用性较好,能为该区干旱监测提供较为科学的理论依据。     

ACCEPTING THE STANDARDIZED PRECIPITATION INDEX: A CALCULATION ALGORITHM1

ABSTRACT: The Palmer Drought Severity Index (PDSI) has been calculated for about 30 years as a means of providing a single measure of meteorological drought severity. It was intended to retrospectively look at wet and dry conditions using water balance techniques. The Standardized Precipitation Index (SPI) is a probability index that was developed to give a better representation of abnormal wetness and dryness than the Palmer indices. Before the user community will accept the SPI as an alternative to the Palmer indices, a standard method must be developed for computing the index. Standardization is necessary so that all users of the index will have a common basis for both spatial and temporal comparison of index values. If different probability distributions and models are used to describe an observed series of precipitation, then different SPI values may be obtained. This article describes the effect on the SPI values computed from different probability models as well as the effects on dry event characteristics. It is concluded that the Pearson Type III distribution is the “best” universal model, and that the reliability of the SPI is sample size dependent. It is also concluded that because of data limitations, SPIs with time scales longer than 24 months may be unreliable. An internet link is provided that will allow users to access Fortran 77 source code for calculating the SPI.     

湖北省旱涝灾害的基本特征与成因分析

湖北省是我国自然灾害多发省份之一，其中旱涝灾害尤为严重，是社会经济发展的一大制约因素。首先研究了湖北省旱涝灾害的基本特征，认为按出现时段，洪涝可分为梅涝、盛夏涝、春涝和秋涝，干旱可分为伏秋干旱、春夏干旱、秋季干旱和冬季干旱，因而具有季节性；各区灾害严重程度不同，干旱可分为鄂东北干旱严重区、鄂东中部伏秋旱严重区、鄂西北春夏旱严重区和鄂西南干旱不严重区，洪涝可分为鄂东中部和江汉平原梅涝区、鄂东北和鄂东南春梅涝严重区、鄂西南夏秋涝区和鄂西北和三峡河谷少涝区，因而具有区域性；此外，还具有延续性、阶段性、周期性和连发性等特征。分析了湖北省旱涝灾害形成的主要因素，认为旱涝灾害是在天气气候因素、地貌因素、环境资源因素、抗灾能力因素、社会经济因素等自然因素和人为因素的共同作用下产生和发展的；旱涝灾害的形成，自然条件固然很重要，但形成严重灾害，则与人为因素有密切关系，这在20世纪表现得尤为明显。     

The need for constructing endangered fish habitats that conform to climate-driven flow changes in a western U.S. river

Warmwater fish habitat in the San Juan River of the southwestern United States has been reduced by over 30% as a result of water depletion, reservoir inundation, and cold-water dam releases combined with drought-related changes in hydrology. This reduction and a suite of other factors have contributed to declines in native fish populations including the federally endangered Colorado Pikeminnow (Ptychocheilus lucius) and Razorback Sucker (Xyrauchen texanus). Conservation efforts for these species include determining flow needs; protecting, managing, and augmenting habitats; and stocking hatchery fish. But the young of stocked fish have low survival due largely to a paucity of nursery habitat not being reformed and maintained under current conditions. Flow recommendations for Navajo Dam releases designed to mimic the river's natural hydrograph have not been met due to water shortages, and the desired outcomes of increased channel complexity and enhanced fish habitat have not been observed. Forecasted hydrology that includes ongoing drought shows that achieving the flow targets through further dam reoperations is unlikely. Mechanical construction of early life-stage habitats is a highly recommended complement to flow management for offsetting the effects of flow reduction and habitat loss. Habitats with features that are effective and resilient under a range of flows are important in counterbalancing the effects of climate change.     

辽西北地区农业干旱灾害风险评价与风险区划研究

以辽西北29个农业县(市、区)为研究区域,选取辽西北最主要的玉米作物作为研究对象,从造成农业干旱灾害的致灾因子危险性、承灾体暴露性、脆弱性和抗旱减灾能力4个方面着手,利用自然灾害风险指数法、加权综合评价法和层次分析法,建立了农业干旱灾害风险指数(ADRI),用以表征农业干旱灾害风险程度;借助GIS技术,绘制辽西北农业干旱灾害风险评价区划图,将风险评价区划图与2006年辽西北受干旱影响粮食减产系数区划图对比,发现两者可以较好的匹配。研究结果可为当地农业干旱灾害预警、保险,以及有关部门的旱灾管理、减灾决策制定提供理论依据和指导。     

近500年我国特大旱灾的研究

基于我国近500年历史旱灾资料,对其中持续特大干旱及旱灾个案进行了分析,并对其规律进行了探讨。指出干旱虽是常见的气候现象,但若是大范围、全流域乃至多个流域的持续干旱,则会酿成大灾。如明崇祯年间的持续数年的特大旱灾造成了水源和粮食的极度消耗,自然灾害导致了经济的全面崩溃,最终导致了朝代的更迭。本文以史为鉴,对我国现代面临的严峻的干旱缺水的形势进行了分析和预测,进而提出应将防范的重点集中在对社会影响极大的特大旱灾上,并且应当针对重旱、极旱的减灾对策及早研究和部署,行动越早就越主动。