Numerical simulation and cause analysis of persistent summer drought during the 1920s in eastern China

In the late 1920’s,a mega-drought in China resulted in widespread crop failure and famine.Sufficient evidence suggests that this drought belonged to a dry period ranging from approximately 1922 to 1932.To understand the characteristics and the cause of this persistent drought period,we combined various data,including observations,tree ring proxy data,reanalysis data,simulation results of the Fifth Phase of the Coupled Model Intercomparison Project and numerical downscaling simulations.The results show that during 1922-1932,most regions in eastern China suffered from a persistent drought that lasted for six years,and the maximum negative precipitation anomaly reached−1.5 times the standard deviation.Given its spatial coverage,duration,and strength,the 1920s drought was unique for the 20th century.The 1920s drought was primarily caused by internal variability.Strong easterlies in lower latitudes,strong monsoon circulation,and abnormally high geopotential heights at middle and upper levels were responsible for the 1920s drought conditions in eastern China;these drought conditions could be further attributed to the joint impact of the Atlantic Multidecadal Oscillation,Pacific Decadal Oscillation and Indian Ocean Basin Mode.