复杂下垫面条件下冬小麦干旱机制辨析及干旱灾害风险研判—以淮河上游地区为例

Drought is one of the serious agricultural meteorological disasters in China, and it is also an important limiting factor for the stable yield and increase of winter wheat.Therefore, it is of great significance to carry out research on winter wheat drought.A case study in the upper reaches of Huaihe River Basin, which is an important winter wheat producing area in China, the following works will be carried out: 1) By using remote sensing digital image processing,GIS(Geographic Information System) spatial analysis method, the complex underlying surface and meteorological observation data of winter wheat planting region were processed by the gridding, and the spatial and temporal pattern of winter wheat drought was refined. 2) Using field experiment of evaporation observation, VIC(Variable Infiltration Capacity) hydrological model and SEBAl (Surface Energy Balance Algorithm for Land)model, from the perspective of "climate - soil - winter wheat" system, the growth water demand and effective rainfall of winter wheat on grid scale was calculated.3) Based on the water balance equation, the spatial distribution characteristics of the water shortage were identified, the water shortage link of winter wheat was clarified and the mechanism of winter wheat drought was discussed. 4) Starting from the link of water shortage, a model of gridding for assessing the drought disaster of winter wheat was constructed. And combined with the forecast data of climate change, the water deficit of winter wheat in different climate change scenarios was simulated, and the spatial and temporal distribution of drought risk was studied, etc.The project attempts to connect microcosmic and macro-scale drought research, explore the water shortage link and mechanism and risk of drought in winter wheat of meso-scale under the influence of complex underlying surface, to provide theoretical basis for the study of the winter wheat drought disaster prevention and mitigation and technical support.

干旱是中国严重的农业气象灾害之一，也是冬小麦稳产增产的重要限制因素，深入开展冬小麦干旱机制和旱灾风险研究可为农业生产提供保障服务。以中国重要冬小麦产区淮河上游地区为例，1)利用遥感图像处理、GIS空间分析方法等将冬小麦种植区复杂下垫面和气象数据格网化处理，细化冬小麦干旱时空格局；2)借助田间蒸散发观测试验、VIC水文模型和SEBAl陆面能量平衡模型，从“气候—土壤—冬小麦”系统角度，测算格网尺度上冬小麦生长需水量、有效降水量；3)基于水量平衡，识别缺水量空间分布特征，明晰冬小麦缺水环节并探讨干旱形成机制；4)从缺水环节出发，构建格网化的冬小麦干旱灾害风险评估模型，结合气候变化预估数据，模拟不同气候变化情景冬小麦缺水量，研判干旱风险时空分布等。尝试连接微观和宏观尺度干旱研究，探索复杂下垫面条件下中观尺度冬小麦干旱缺水环节、干旱形成机制和风险，为冬小麦干旱防灾减灾研究提供理论依据和技术支持。

基于1961～2016年140个气象站点的日尺度降水数据和2000～2016年的月尺度的地表温度、归一化植被指数，利用标准化降水指数表征淮河流域气象干旱，利用温度植被干旱指数表征淮河流域农业干旱，时间上，轻度和重度以上干旱占比在冬前生长期和灌浆成熟期呈现下降趋势，越冬期和返青抽穗期呈现上升趋势。空间上，不同生育期的干旱分布规律不明显，但总体上呈现南低北高和沿海至内陆递增的分布规律。冬小麦农业干旱的轻度以上干旱所占比重要大于冬小麦气象干旱，表明淮河流域农业干旱程度大于气象干旱。.年际变化上：冬小麦需水量冬前生长期下降，到返青抽穗期和灌浆成熟期呈现上升趋势；就有效降水量而言，冬前生长期和越冬期年际变化上升趋势明显，返青抽穗期和灌浆成熟期下降趋势较为明显；就缺水量而言，冬前生长期和越冬期年际变化下降趋势明显，返青抽穗期和灌浆成熟期上升趋势较为明显。空间变化上：冬小麦需水量冬前生长期东西低，南北和中部高；越冬期中部低南北部高；返青抽穗期东南和西南低，西部和南北高；灌浆成熟期北高南低。有效降水量各个生育期基本呈现南高北低的纬向地带性规律。冬小麦缺水量冬前生长期与越冬期同需水量分布特征较为相似，返青抽穗期与灌浆成熟期同有效降水量分布特征较为相似。.运用综合层次分析法和熵权法构建冬小麦干旱危险性、暴露度、脆弱性和防灾减灾能力指标体系，通过综合干旱风险评估模型进行冬小麦干旱风险评估。结果表明：空间上，淮河上游冬小麦干旱风险程度在东北(驻马店市辖区)、西南(孝感市辖区)最高,中西部(信阳市辖区)风险最低。时间上，5-6月冬小麦干旱风险最高，11-12月风险最低。.2021-2100年冬小麦干旱风险的空间分布呈纬向分布，干旱风险自南向北逐渐变强。不同路径下干旱风险程度差异较大，除SSP1 路径未出现高风险地区外，SSP2 与SSP5路径下冬小麦干旱风险程度较高。空间分布上，冬小麦干旱高风险的区域主要分布在上游地区的北部与东部，而低风险主要分布在西部及南部。