长江中下游流域多尺度干旱监测指标的适应性研究

The drought is complex climate disasters, frequent and continuous drought will bring great losses to the national economy. At present the drought disaster increasingly threats to China's grain, ecological safety seriously, and restricts the development of national economy, thus it becomes a pressing problem to increase the level of drought monitoring and warning, to enhance the ability of drought disaster defense. The drought index is the basis and the core for monitoring drought, but there is no unified index can accurately describe any regional drought, because of the complexity of drought causes and climate influence. So it has important significance in the applicability of the drought index, and the establishment of regional drought monitoring index. This project is to establish objective and accurate meteorological drought index system for wet area by using the station observations, supplemented by 1-2 stand soil moisture-energy cycle-land surface process observation data, analysing the adaptability of SPEI, PDSI and CI in the mid and lower reaches of Yangtze river basin. To find out the evolution characteristics of the soil water content, crop water requirement and soil water evaporation for the main crop types in different seasons when the drought occurred, and finaly, put forward the improvement and perfect technical method to establish the objective and accurate meteorological drought index system, to built up a reliable scientific basis for precise drought warning systerm in the wet area.

干旱是复杂的气候灾害，频繁和持续的干旱会给国民经济带来巨大损失。目前干旱灾害正日益严重地威胁着我国粮食、生态安全，制约着国民经济的发展，因此提高对干旱灾害的监测及预警水平，增强防御干旱的能力已成为急待解决的重要问题。干旱指标是监测干旱的基础和核心，但由于干旱成因和气候影响的复杂性，目前还没有一个统一指标能准确描述任何区域的干旱。所以开展干旱指标的适用性研究，建立区域干旱监测指标具有重要意义。本项目拟通过分析气象台站历史资料，并辅以1-2个站土壤-水分-能量循环的陆面过程观测资料，分析长江中下游地区不同季节主要作物类型在降水偏少并发生气象干旱时，土壤含水量、作物需水量、土壤水分蒸发等特征及演变规律，并在不同时间尺度上，就SPEI、PDSI和CI在长江中下游地区的适应性进行研究，提出改进与完善的技术方法，建立针对湿润地区客观准确的气象干旱指标体系，为准确发布干旱演变预警信息提供可靠的科学依据。

干旱指标是研究干旱气候的基础，也是衡量干旱程度的关键环节，由于干旱自身的复杂性和对不同地域影响的差异性，任何干旱指标都很难达到在时空上普遍适用的条件，因此，在研究区域干旱时必须选择适宜区域范围的指标。本项目利用40多年的观测资料，对PDSI指数及CI指数在长江中下地区进行了订正，计算了不同时间尺度的SPEI指数、PDSI指数及CI指数，对比分析了中国气象灾害大典、中国气象灾害年鉴及气象服务信息等的干旱过程，对它们的适应性进行了验证，初步建立了针对长江中下游湿润地区的客观准确的气象干旱指标体系。基于干旱指数的应用分析，进一步对干旱成因进行了的诊断研究，结果表明，青藏高原200 hPa上空风场的季节内振荡的变化及传播与长江中下游地区多雨年夏季降水关系密切；但是在少雨年这种低频变化的影响只是一种必要条件。对干旱成因的对比分析发现，源于大西洋的Rossby波的频散与大气遥相关的不同组合，是不同季节造成长江中下游地区干旱主要机制。