Study on Drought Evolution Characteristics and Teleconnection Driving Forces Based on Vegetation Condition Index in China
Drought will cause vegetation greenness decline,crop yield reduction,biological habitat destruction and other problems,which have a significant impact on human and natural environment.In this paper,the vegetation condi-tion index(VCI)was adopted as a drought indicator,and the extreme-point symmetric mode decomposition(EPSMD)method was used to identify the periodicity and trend of the VCI series from 1999 to 2019 across China.Subsequently,the gridded trend test method was applied to reveal the drought trend characteristics at the grid scale.The multivariate wavelet coherence technique was utilized to explore the internal relationship between drought and various teleconnection factors.The results indicate that the VCI-based drought showed a decreasing trend during 1999-2019 across China,with a linear tendency rate of VCI of 0.044/10a;The characteristics of drought were different in various sub-regions,among which the drought mitigation trend was the most obvious in the Loess Plateau with a linear tendency rate of VCI of 0.215/10a;The gridded average Z-values of VCI trend characteristics at the grid scale were 0.41,0.79,0.50,and 0.11 in spring,summer,autumn,and winter,respectively,indicating that drought showed a decreasing trend in each season;The combination of remote correlation factors PNA-ENSO has the most obvious impact on drought in China.PNA and ENSO can be used as drought warning input factors to improve the accuracy of drought forecasting.
NETL
NSTL
万方数据
维普
