Spatiotemporal pattern of drought in Loess Plateau of Gansu Province, Northwest China in 1961-2010

Drought, one of the most severe hazards resulting in significant economic losses in agriculture and industry, is a natural phenomenon caused by the imbalance between the input of and the demand for water. As a major grain production zone in Gansu Province, the Loess Plateau of the Province shows great vulnerability in drought. In this paper, the characteristics of inter-annual and seasonal droughts in the Loess Plateau of Gansu Province were analyzed in terms of drought rate, drought intensity, and drought frequency, and by using the compound index of meteorological drought (CI) and the data of daily precipitation, air temperature, wind speed, relative humidity, and sunshine duration from 33 weather stations during the period from 1962 to 2010. Kriging interpolation was also applied to calculate the CI value for each station, so that all the CI values could be spatially and temporally comparable. In the Plateau of the Province, drought rate showed a significant increasing trend in spring and autumn but a slight increasing trend in summer and winter, and drought frequency was the most in summer, followed by in spring and autumn, and in winter. The 50-year average drought rate in spring, summer, autumn, and winter was 53.26%, 65.18%, 42.2%, and 44.16%, respectively. Over the past 50 years, the most serious inter-decadal drought in the Plateau of the Province occurred in spring and autumn since 2000, and in winter in the 1980s. In the 1970s and 1980s and since 2000, summer drought was more serious. There was a notable inter-annual fluctuation in the average annual lasting days and annual occurrence severity of meteorological droughts in the whole region, and their linear change tendency was obvious. Spatially, in spring, summer, and autumn, the drought-prone area was mainly located in the northwest of the region. Meanwhile, in the districts of Lintao-Tongwei-Tianshui and southeast of Qingyang, the change range was the largest. The drought-prone area in winter was mainly located in south of the region. In order to well prevent and mitigate the drought in the Loess Plateau of Gansu Province, government and agricultural managers should pay more attention to the droughts that occur from spring to autumn, especially in summer.