关键词: 作物水分亏缺指数（CWDI）, 春玉米, 中国北方, 旱作农业, 时空变化

Abstract: Based on the daily climate data of 156 meteorological stations in the dry farming area of northern China during 1961-2018 and the data of the spring maize growth period during 1991−2013, the dryland area in northern China was divided into four sub-areas according to the aridity index. Based on the crop water deficit index (CWDI), the temporal and spatial characteristics of spring maize drought in dryland area of northern China were revealed by analyzing water supply and demand, inter-annual variation of CWDI, drought station ratio, and frequency. The results showed that :(1) the water supply and demand in Ⅰ（humid area）and Ⅱ（sub-humid area）areas were balanced, while the water supply and demand in Ⅲ（sub-arid area）and Ⅳ（arid area）areas were unbalanced. The mean square error of precipitation in area Ⅰ was up to 70mm, and the interannual variation range of CWDI was the largest. In the 1970s, CWDI floated sharply in the sowing-seedling and seedling-jointing stages. CWDI in area II fluctuated greatly during the tasseling-milking stage in the 1980s. In area Ⅲ, CWDI increased at the rate of 1.06pp10y⁻¹(P<0.05) during the tasseling-milking stage, and the interannual drought tended to expand. There was little interannual change in area Ⅳ. (2) During 1961−2018 the ratio of drought stations in the tasseling-milking stage increased significantly at the rate of 2.58pp10y⁻¹(P<0.05), and the average of extra severe drought was 14.95%. There was no significant change in the other four growth stages. During the tasseling-milking stage, the drought level was the most severe, and the drought range was significantly expanded. (3) In terms of spatial distribution, drought grade and frequency showed an obvious east-west distribution. The frequency of slight drought in eastern and southwestern Heilongjiang province, western Jilin, and western Liaoning province (area Ⅰ and Ⅱ) is more than twice in three years. In the Zhangcheng district (the cities of Zhangjiakou and Chengde in Hebei, area Ⅲ), the frequency of moderate drought during the stage of sowing-seedling reached more than once in 5 years. In Mu Us Desert (it is located between Yulin, Shaanxi province and the Ordos, Inner Mongolia Autonomous Region, area Ⅳ), the frequency of extra severe drought in the jointing-tasseling stage reached twice in 3 years, and the period of jointing-tasseling was mainly threatened by extra severe drought.

Key words: Crop water deficit index (CWDI), Spring maize, Northern China, Dry farming, Spatial-temporal variation