Abstract: 【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.

Key words: winter wheat , winter drought , spring drought , climate change , meteorological drought , North China