1962-2010年潜在干旱对中国冬小麦产量影响的模拟分析

旱灾是冬小麦生产中常见的气象灾害,该研究旨在了解气候变化背景下中国冬小麦小麦受干旱的历史影响及变化情况,这对合理指导冬小麦生产的减灾、防灾,稳定冬小麦产量有重要的指导意义和作用。该研究采用CERES-Wheat模型,模拟了1962-2010年潜在干旱对中国冬小麦产量影响的时空变化趋势,并分析其与大气环流因子间的关系,以期了解中国近50a来冬小麦受旱程度的变化情况。结果表明:1)1962-2010年中国冬小麦因干旱造成的潜在产量损失总体呈上升的趋势,但不同时期表现不同,其中20世纪60年代、20世纪80年代表现为下降趋势。2)在过去近50a里,中国冬小麦潜在旱灾产量损失中心有向西北移动的趋势,这主要是受黄土高原和河西走廊地区受旱程度增强的影响。3)中国冬小麦潜在旱灾产量损失中心的经纬度和影响中国降水的副热带高压、北极涡系统的部分指数具有显著的负相关关系。冬小麦生长季同期(前一年10月-当年5月)的副热带高压系列指数与中心的相关关系表现显著,而生长季同期和生长季前期(前一年6月-前一年9月)的北极涡系列指数与中心都具有显著的相关关系。当冬小麦生长季同期北半球的西太平洋副高、印度副高和南海副高的强度偏强、范围偏大时,潜在旱灾产量损失中心的位置将会偏西;当北极涡在冬小麦生长季前期或同期偏大偏强时,中国冬小麦潜在产量损失中心将偏南,反之亦然。

Simulation of winter wheat yield influenced by potential drought in China during 1962-2010

Abstract: Frequency of extreme weathers is projected to increase under the scenario of climate change, which can cause extensive damages on crop production. Wheat is one of the most important staple crops in China, and drought is the main climate disaster affecting its yield, particularly in northern parts of the country. The temporal and spatial changes of drought impacts under climate change on wheat are therefore a great concern. Most previous studies investigated the drought impacts through the use of climate indices, such as SPI. The climate indices usually neglect the diverse responses of different crop growth stages to a certain degree of drought shock, and they also disregard the contrasting characteristics in terms of the drought resistance between crop genotypes. This study assessed the potential yield impacts of past drought anomaly (1962-2010) on winter wheat, by using a process-based crop model CERES-Wheat. The model was driven by daily weather data and soil data at a grid scale of 50 km ×50 km. The output of rainfed and fully irrigated yields were retrieved for further analysis. We used the difference between simulated irrigated and rainfed wheat yields to define a potential yield loss caused by drought. The anomaly percentage of the potential yield loss was employed to reflect the interannual and interdecadal variation of estimated impact of drought on winter wheat. We investigated the moving of drought susceptible regions by calculating a geographically drought-affecting center for each 10-year period from 1962 to 2010 (1960s: 1962-1970, 1970s: 1971-1980, 1980s: 1981-1990, 1990s: 1991-2000, 2000s: 2001-2010). Finally, the relationships between estimated yield impacts and recorded indices of atmosphere circulation was examined to understand the underlying mechanisms of past drought risks. The indices were averaged over the prior to winter wheat growing-season (June-Sept.) and the whole growing-season (Oct.-May), respectively. Our results demonstrated that simulated winter wheat yield exhibited a fast decreasing rate under the rainfied environment than that under the full irrigated condition, resulting in a slight increase of estimated potential yield loss from 1962 to 2010. These suggest that overall past climate change has caused increased drought risks for winter wheat production in China. Northwest China, especially the Loess Plain and Hexi Corridor showed the fastest increase of the drought risks among all winter wheat growing regions of China. However, the potential yield loss experienced a decrease in a few simulated time periods, such as the1960s and the 1980s, suggesting obvious temporal fluctuation and variability of the drought risks under climate change. Furthermore, the inferred primary drought susceptible areas moved toward northwest during the past 50 years, indicated by the drift of the geographically drought-affecting centers. This moving is interpreted by the increased yield loss due to drought in northwest China, especially in the Loess Plain and Hexi Corridor. The moving of the drought susceptible areas was fast in the periods of 1960s-1970s and 1980s-1990s, probably caused by the associated changes in precipitation and temperature patterns. In addition, the estimated yield loss and the moving of the drought-affecting center demonstrated significant (P<0.05) correlations to a number of atmosphere indices (i.e. North Pole Vortex, subtropical high system). A stronger subtropical high system during the winter wheat growing season associated with a west moving of the drought-affecting center. A stronger North Pole Vortex before or during the winter wheat growing season associated with a south moving of the drought-effecting center.