Application of atmospheric low-frequency oscillation on meteorological drought forecast in Eastern part of the Northwest China

Abstract

Characteristics of the atmospheric low-frequency oscillation on the drought process during the flood season (May to September) in eastern part of the northwest China are analyzed using the NCEP/NCAR reanalysis data and conventional surface precipitation data. Results show the low-frequency characteristics of the southward and eastward propagation in the middle and high latitudes, and the divergence airflow over eastern part of the northwest China during the drought. Drought event occurs during propagation of the low-frequency north wind and before convergence of the north and south airflows. The drought process mainly occurs in the negative phase of relative vorticity low-frequency oscillation and in the positive phase of the OLR low-frequency oscillation, i.e., in the period of relatively weak convection. A method based on the atmospheric Low-Frequency diagnosis was used to predict the meteorological drought event in eastern part of the northwest China. The forecast results are promising on the meteorological drought event during the flood season from 2010 to 2017.