Nonlinear characteristics of hydroclimate variability in the mid-latitude Asia over the past seven centuries

Abstract

Hydroclimate variations in the mid-latitude Asia have received considerable attention due to its significance for the regional ecosystem and livelihood, while its nonlinear characteristics over the past centuries are not fully understood yet. Hydroclimate patterns for the mid-latitude Asia are classified into eastern and western modes based on a network of the reconstructed Palmer drought severity index (PDSI) of 197 grids spanning since 1300. The hydroclimate variations of western mode are more complex than that of eastern mode based on the Higuchi’s fractal dimension (HFD) analysis, which may be related to the complex atmospheric circulation patterns that dominate them. The relationships of the hydroclimate variations between western and eastern modes at different time scales extracted by ensemble empirical mode decomposition method (EEMD) are detected. The anti-phase relationship of the hydroclimatic variations between western and eastern modes at the interdecadal variations occurs during the periods with the enhanced El Nino Southern Oscillation (ENSO) variance. Similarly, the multidecadal hydroclimate variations are anti-phase when the Pacific Decadal Oscillation (PDO) is in its warm phases. The inverse relationship between western and eastern modes is stable for the centennial scale.