1961-2010年中国主要麦区冬春气象干旱趋势及其可能影响

【目的】近年来，连续发生的冬春连旱事件已经严重威胁到冬小麦的安全生产和粮食增产，本研究以中国主要麦区为研究对象，分析1961-2010年中国北方主要麦区冬春季降水、无降水日数和极端干旱频率的变化趋势及其对当地冬小麦生产的可能影响，揭示冬春干旱在当前气候背景下的演变趋势，为科学应对冬春干旱提供依据。【方法】采用线性倾向估计与Robust F线性显著性检验分析1961-2010年中国北方各站点冬春季降水、冬春季无降雨日数的线性倾向与显著性，揭示冬季、春季和冬春季的降水和无降雨日数的年代际变化趋势；根据气象干旱等级的国家标准GB/T 20481-2006将干旱5个等级中的重旱和特旱定义为极端干旱，基于降水距平的滑动平均，计算1961-2010年各年冬春季极端干旱频次的线性倾向，分析极端干旱发生频次的年际变化趋势和干旱风险剧增区降水的时间变化，揭示干旱时间动态趋势。【结果】(1)1961-2010年，华北为中心的冬麦区冬春气象干旱呈加剧趋势，其中心区域山西、河北和山东西北部冬春两季极端干旱的频次呈现增加趋势，陕西东部和湖北西北部春极端干旱的频次也呈增加趋势；(2)1961-2010年华北冬麦区的冬季降水呈减少趋势，且无降水日数呈增加趋势，即冬季气象干旱呈加剧趋势,其他区域的冬季降水呈增加趋势，无降水日数呈减少趋势；(3)1961-2010年华北冬麦区、黄淮冬麦区中南部和西北春麦区南部的春季降水均呈减少趋势，且无降水日数呈增加趋势,其他区域春季降水呈增加趋势，无降水日数呈显著减少趋势；(4)从重点区域降水的时间动态看，近20来华北地区的冬季和春季降水呈急剧下降趋势，无降水日数呈显著增加趋势，冬春气象干旱风险呈剧增趋势；近50年来黄淮冬麦区和长江中下游冬麦区的冬季降水呈增加趋势，而春季降水呈下降趋势，无降水日数呈增加趋势，长江中下游麦区20世纪70年代中期以后春季降水呈持续下降趋势。【结论】华北地区冬春季降水呈急剧下降趋势，无降水日数呈增加趋势，华北冬小麦冬、春干旱势必由于地下水位的持续下降和抗旱成本的增加而导致干旱风险加大；黄淮冬麦区南部和长江中下游冬麦区的春季降水尽管也呈下降趋势，由于该区域春季平均降水量对小麦来说以偏多为主，降水减少还不会影响到小麦生长，该区域降水的减少可能对冬小麦生长有利；气候干旱区东北和内蒙春麦区、西北春麦区西部50年来的冬春季降水呈增加趋势，有利于春小麦生产。

Meteorological Drought Trend in Winter and Spring from 1961 to 2010 and Its Possible Impacts on Wheat in Wheat Planting Area of China

【Objective】Continuous occurrence of winter and spring drought events in recent years has seriously threatened the safety production and grain increase of winter wheat in the north of China. This study focused on the main wheat growing areas of China, precipitation, no precipitation days and frequency of extreme meteorological drought trend in winter and spring from 1961 to 2010 and its possible impacts on wheat in wheat planting area in north of China.【Method】Trend analysis of precipitation, no precipitation days and frequency of extreme meteorological drought for the 1961-2010 period using data from 329 meteorological stations located in the wheat growing regions in the north of China. The linear trend and significance of precipitation and no precipitation days in different regions in north of China was analyzed using the methods of regression analysis, inverse distance weighted and robust F linear significant test. The precipitation, no precipitation days and frequency of extreme meteorological drought of interannual and decadal variation trend was analyzed. Based on the sliding average precipitation anomaly, the linear tendency of annual extreme drought frequency in winter from 1961 to 2010 was calculated, and the interannual variation trend of extreme drought frequency and changing trend of precipitation in different regions were analyzed for exploration of the temporal dynamic trend of drought. According to the GB/ T20481-2006 national standards of meteorological drought classification, the severe drought and specially drought of drought grade were defined as extreme drought. According to the different climate characteristics of wheat growing regions in China, the main wheat growing area is divided into six zones as follows in order to quantify the different drought trends in the north of China. ① The Northeast China spring wheat region: Heilongjiang Province, Jilin Province and Liaoning Province; ②The Inner Mongolia spring wheat region including the Inner Mongolia Autonomous Region. ③ The Northwest China spring wheat region including Gansu Province and Ningxia Autonomous Region. ④ The North China winter wheat region including Hebei Province, Shanxi Province, Shaanxi Province, Beijing and Tianjin. ⑤The Huang-Huai Plain winter wheat region including Shandong Province, Henan Province, Jiangsu Province and Anhui Province. ⑥ The middle and lower Yangtze River winter wheat region including Hubei Province, Hunan Province, Jiangxi Province, Zhejiang Province and Shanghai.【Result】 In the winter wheat growing region of North China and north of the Huang-Huai Plain, as well as in spring wheat area of Northwest China, the precipitations in winter and spring decreased in the last 50 years with a particular sharp decline after 1990, the frequency of extreme drought showed an increasing trend. The precipitations in winter and spring decreased in the last 50 years in the east Shaanxi and northwest Hubei, the frequency of extreme drought in Hebei province, Beijing, Tianjin, Shanxi province and west of Shandong increased in 1961-2010. Winter and spring precipitation and the number of precipitation days showed an increasing trend in the Northeast China, Inner Mongolia and Northwest China''s southern spring wheat region. Winter and spring precipitation and the number of precipitation days showed a decreasing trend in a part of Huang-Huai Plain winter wheat area, the southern part of the North China winter wheat region, the southeast and northwest spring wheat regions and the middle and lower Yangtze River winter wheat region. A sharp decline in winter precipitations were observed in the last 50 years in North China, and no precipitation days showed an increasing tendency, and the meteorological drought aggravated. The winter precipitation decreased and no precipitation days increased in Hebei Province, Beijing, Tianjin, Shanxi province and the western Shandong Province in 1961-2010. The winter precipitations increased in other areas, and no precipitation days decreased. The spring precipitations showed a decreasing tendency in North China, Central and southern Huang-Huai Plain and southern of Northwest China in 1961-2010, the largest decline up to 20 mm/10a. The no precipitation days showed an increasing tendency, the largest increased up to 1-1.5 d/10a. Among the seven sites, precipitation was significantly decreased in Shaanxi, the decrease rate up to 10-20 mm/10a. The no precipitations days showed a significant decreasing tendency in most areas in Shaanxi, the west of Henan, Jiangxi and Zhejiang, the decrease rate up to 1-1.5 d/10a. The spring precipitations increased in other areas, and no precipitation days decreased in the last 50 years. Temporal dynamics of key regional precipitation showed a sharp decline in winter and spring precipitations in the last 20 years in North China and no precipitation days showed an increasing tendency, the winter and spring meteorological drought aggravated. The winter precipitations increased in the Huang-Huai Plain winter wheat region and the middle and lower reaches of the Yangtze River, and the no precipitation days decreased in the last 50 years. But the spring precipitation decreased and the no precipitation days increased after the mid 1970’s.【Conclusion】Dramatically decline of winter and spring precipitations could have a potential negative impact on future winter wheat production in North China because of the shortage of water resources available to wheat growth. The decline of precipitations during spring would not affect growth of wheat in south of the Huang-Huai Plain and the middle and lower zones of the Yangtze River. This is because the spring precipitations are still enough for wheat to avoid drought stress. The winter and spring precipitation patterns in Northeast China, Inner Mongolia, and Northwest China increased over the 1961-2010 period, which would benefit spring wheat production.