Spatial-Temporal Characteristics of Drought and Spring Maize in Eastern Gansu
近50年来甘肃省河东地区春玉米干旱时空特征分析

The total number of droughts is increasing in China due to global climate change. Extraordinary droughts are of a long duration, wide range and severe disaster degree. Eastern Gansu is located in the semi-arid-semi-humid climate zone, and is a rain fed agricultural region. Because the distribution of precipitation is uneven, the water requirements of spring maize are different during various growth stages. Understanding the temporal and spatial distribution and evolution of droughts during spring maize is important to the sustainable development of the economy. Here, according to 50 years of weather data from seven meteorological stations in eastern Gansu, the water requirements of spring maize at different growth stages was calculated using the FAO Penman-monteith model and coefficient. The crop water deficit index (CWDI) was calculated and the drought grade was divided into four communities. The results show that the CWDI became larger initially and then smaller during the growth period for spring maize; the ten days, middle and last ten days of June contained maximum values. The CWDI of every ten days was over 10%, showing that precipitation in the growth period cannot meet the water requirements of spring maize. The frequency of different classes of drought were 8%~20% for light drought, 7%~ 23% for middle drought, 0~17% for heavy drought, and 0~47% for excessive drought. The relative severity of the drought followed the pattern: tasselling stage to flowering stage > jointing stage > pre-milk stage > emergence stage to seven leaf stage > late-milk stage to mature stage. In the last 50 years, the severity of droughts has increased in this area.