Study On Spatial-temporal Characteristics Of Drought In China During 1981-2015 Based On VCI

Drought is one of the most serious natural disasters.Thus,drought monitor is important for improving agricultural production,protecting the environment and promoting the sustainable development of social economy.The vegetation condition index(VCI)obtained from NOAA/AVHRR during 1981-2015 were used as the drought indicator,and the spatial-temporal variation characteristics were analyzed by using drought frequency analysis,trend analysis,anomaly index analysis and Mann-Kendall test.Meanwhile,meteorological drought trend and frequencies during 1981-2010 were analyzed with meteorological drought composite index(CI).Pearson correlation analysis was used to study the correlation and hysteresis between VCI and CI.The auto-regressive integrated moving average(ARIMA)model was used to forecast drought changes in the future.The results obtained are as follows: During 1981-2015,though the summer VCI in the southern region was on the decline,VCI of most areas in China exhibited an upward trend,indicating that drought had a downward trend on the whole.China was the high frequency area of drought,but most areas were mainly concentrated on slight and moderate drought.The frequencies for sever drought were relatively low.In addition,drought occurred with obvious seasonal and geographical difference,the frequencies in northern and southern regions were higher,especially in spring and autumn;and the frequencies in the Tibetan Plateau and northwestern regions were much lower except for Sinkiang,northern Inner Mongolia and southern Tibet.Mann-Kendall test further suggested that in the northern region,the drought mutation was not significant during the four seasons,but it mutated in other geographic regions and mostly occurred in spring and winter.There was a great difference between north and south in meteorological drought trend,which decreasing in southern region while rising in northern region.The space distribution of meteorological drought frequencies showed features of “higher in north and lower in south”,and frequencies of slight drought and moderate drought were higher,and the frequency of severe drought and excessive were lower.Besides,VCI was seasonal related with meteorological drought,which was positively related in spring and summer,and negatively related in winter and autumn in northern and southern regions.In the Tibetan Plateau,VCI was negatively related with meteorological drought in spring.All these proved VCI a reliable drought indicator.The drought prediction results showed that the drought situation in our country will be alleviated to some extent in the future except for the southern region.