<p>The Atlantic Multidecadal Oscillation (AMO) experienced negative-to-positive phase transitions around the late 1920s and late 1990s. The present study investigates interdecadal changes in Asian persistent drought characterized by the 24-month Standardized Precipitation Evapotranspiration Index (SPEI) under the influence of the AMO phase transitions. Distinct Asian persistent drought changes are found corresponding to the two AMO phase transitions. The first AMO phase transition around the late 1920s is accompanied by a change to a drier condition in most of eastern China and to a wetter condition in western Asia and northeastern Asia. The second AMO phase transition around the late 1990s is followed by a change to a drier condition in most of the mid-latitude Asia. Both precipitation and temperature changes contribute to the persistent drought changes with a larger role of precipitation. The distinct Asian persistent drought changes corresponding to the two AMO phase transitions are attributed to different atmospheric circulation anomaly patterns that induce different precipitation and temperature changes through modulating vertical motion, soil moisture and surface heat fluxes. The distinct atmospheric circulation changes during the two AMO phase transitions are induced by both different AMO-related sea surface temperature (SST) changes in the North Atlantic Ocean and the opposite Pacific Decadal Oscillation (PDO) phase transition-related SST changes in the North Pacific Ocean. The present study highlights the necessity to distinguish the influences of individual AMO phase transitions and to consolidate the combined effects of the AMO and PDO phase transitions in addressing the interdecadal climate variability.</p>

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Interdecadal changes in persistent drought over Asia under phase transitions of the Atlantic Multidecadal Oscillation

  • Jianmin Zhang,
  • Renguang Wu,
  • Xiaojing Jia

摘要

The Atlantic Multidecadal Oscillation (AMO) experienced negative-to-positive phase transitions around the late 1920s and late 1990s. The present study investigates interdecadal changes in Asian persistent drought characterized by the 24-month Standardized Precipitation Evapotranspiration Index (SPEI) under the influence of the AMO phase transitions. Distinct Asian persistent drought changes are found corresponding to the two AMO phase transitions. The first AMO phase transition around the late 1920s is accompanied by a change to a drier condition in most of eastern China and to a wetter condition in western Asia and northeastern Asia. The second AMO phase transition around the late 1990s is followed by a change to a drier condition in most of the mid-latitude Asia. Both precipitation and temperature changes contribute to the persistent drought changes with a larger role of precipitation. The distinct Asian persistent drought changes corresponding to the two AMO phase transitions are attributed to different atmospheric circulation anomaly patterns that induce different precipitation and temperature changes through modulating vertical motion, soil moisture and surface heat fluxes. The distinct atmospheric circulation changes during the two AMO phase transitions are induced by both different AMO-related sea surface temperature (SST) changes in the North Atlantic Ocean and the opposite Pacific Decadal Oscillation (PDO) phase transition-related SST changes in the North Pacific Ocean. The present study highlights the necessity to distinguish the influences of individual AMO phase transitions and to consolidate the combined effects of the AMO and PDO phase transitions in addressing the interdecadal climate variability.