Copula-based interannual variability of winter–spring hot drought events over the low-latitude highlands of China

Abstract

Recurrent and prolonged severe hot droughts during the winter–spring period across the low-latitude highlands of China (CLLH) have caused major problems in recent decades, including disruption to the growing season of crops, drinking water shortages, and degradation of ecosystems. This study, which focuses on the period 1979–2022, uses reanalysis datasets and data generated as part of the Coupled Model Intercomparison Project Phase 6 (CMIP6) to investigate the causes of these winter–spring hot droughts in the CLLH. The results indicate that the occurrence of droughts has a monopole distribution that is closely associated with the circumglobal teleconnection (CGT). During the positive phase of the CGT, the CLLH is influenced by an anomalous anticyclone and northeasterly winds that induce an anomalous descending motion in the troposphere. This in turn leads to a northeasterly moist enthalpy flux and divergence anomalies that ultimately cause a decrease in precipitation and an increase in temperature over the CLLH, and hence hot drought events. Conversely, during the negative phase of the CGT, these processes are reversed and the CLLH is subject to increased precipitation and lower temperatures. In addition to atmospheric internal variability, anthropogenic forcing has increased the probability of extreme hot droughts by about 1.86 times.