CR prepress abstract  -  DOI: https://doi.org/10.3354/cr01500

Nonlinear changes in aridity due to precipitation and evapotranspiration in China from 1961 to 2015

Yunhe Yin*, Danyang Ma, Shaohong Wu

*Email: yinyh@igsnrr.ac.cn

ABSTRACT: Changes in regional aridity have complicated spatial-temporal features during the past several decades and imposed important implications on hydrologic cycles under global climate change. However, nonlinear changes in aridity and its spatial variability in China remain poorly understood. Here, we analyze the spatial-temporal changes in hydroclimatic variables, including reference evapotranspiration (ETo), precipitation (P), aridity index (AI) and their relationships, mainly based on the Ensemble Empirical Mode Decomposition method. A climate dataset from 573 meteorological stations in China was used for the period 1961-2015. The results show that the nonlinearity of changes in aridity was complex with distinct spatial difference. Approximately 76.09% of stations showed reversed trends in AI during 1961-2015, among which AI first decreased and then increased, mainly in Inner Mongolia and the areas south of the middle and lower reaches of the Yangtze River. Nevertheless, their reversed times were not constant. The drying to wetting transition mainly occurred in northern areas, including the southern part of Northeast China, the east of the Loess Plateau and the southern North China Plain. Although majority stations experienced reversals from downward to upward trends of ETo (53.92%) mainly around the 1990s, the increasing precipitation exerted larger effect on AI. For most eco-geographical regions in China, the nonlinear variations in ETo and P jointly led to the decline in AI over the past 55 years, and the P trend contributed more than the ETo trend to the change in AI, except for the subtropical regions, where ETo variations played a key role.