Analysis of spatio-temporal characteristics of drought for maize in Northeast China

Based on the observation data of temperature,precipitation,wind,vapor pressure and sunshine hours collected from 124 weather stations during 1961～2007 and the Penman-Montieth equition,the potential evapotranspiration(ET0) and Miaze water requirement(ETC) were calculated,the maize crop water deficit index(CWDI) of different classes of drought were detemined and the frequencies of different classes of drought in Northeast China were calculated.The results showed that there were significant seasonal and spatial distribution characteristics.Drought occurred in high frequency at the stage of seedling,secondly,filling-maturity stage,and the occurring frequency of slight drought or above in various growth stages of maize showed an increasing trend from northeast to southwest.In the major dry areas,the drought occurring frequency in seedling,jointing-booting,tasseling-silking and filling-maturity stages was 60%～96%,30%～58%,20%～40% and 30%～52%.For inter-decade change characteristics,drought fluctuation was moderate in the 1960～1980 s, while it turned an increasing trend since the early 1990 s,especially after the mid 1990 s,and it maintained at a high level in 2000～2004.Therefore,drought increased significantly in Northeast China in the recent 10 years and it occurred in each stage of maize development.