The Temporal Variation Characteristics and Spatial Distribution Laws of Drought of Spring Maize in Northern China

【Objective】 The tendency of inter-decadal evolution characteristics and spatial distribution laws of drought of spring maize at each growth stage in northern China were studied. 【Method】 Based on the daily meteorological data and spring maize growing records of 291 meteorological stations during 1961-2010 in the study area, the tendency of inter-decadal evolution characteristics and spatial distribution laws of drought of spring maize in the study area were analyzed using the crop water deficit index as the agricultural drought index.【Result】As for the CWDI of spring maize, the fluctuations in different years in Northwest China was steady, while in the other two areas in 1980s and 1990s the fluctuations were relatively severe. And the CWDI of spring maize at the stage of tasselling to maturation in North China was lower than the other two stages significantly, while the changes in Northeast China and Northwest China at different growth stages were not obvious. There was a significant fluctuation of the classification of drought during different decades in the central region of North China. The spatical distributions of the classification and frequency of drought of spring maize in northern China showed higher in west and north and lower in east and south, they both had the highest value in Northwest China, followed by North China, and the lowest value in Northeast China. Results showed a significant spatial distribution of the frequency of extreme drought and light drought. The extreme drought was mainly concentrated in most of Xinjiang, the north part of Gansu and the northwest reigon of Inner Mongolia. It occurred two times or above in three years. While the light drought was mainly concentrated in most of Northeast China, most of North China and the southeast part of Northwest China. It occurred one time or above in five years. Moderate drought and severe drought were mainly concentrated in North China and the east part of Northwest China. They occurred one time or above in five years, and they had a decreasing trend with growth stages changing. 【Conclusion】 As for the CWDI of spring maize in northern China, the fluctuations in different years in North China and Northeast China were relatively severe, and there was an upward trend since 1980s. The spatical distributions of the classification and frequency of drought indicated a significant east-west distribution. The extreme drought happened in higher frequency in the west and lower in the east, and it has expended in the stage of tasselling to maturation, on the contrary, the light drought occurred in higher frequency in the east and lower in the west, and it had increased at the stages of tasselling to maturation.As for the moderate drought and severe drought, they both showed a higher frequency in central regions and a lower frequency in east and west regions, and they decreased both in area and degree at the stages of tasselling to maturation. The sensitive area of drought grade variation at different growth stages were the north part of Xinjiang and the central region of North China.