Abstract:In this study, the NCEP/FNL reanalysis and the WRFV3.9.1 is used to investigate the influence of the intensity of the monsoon depression on the rainstorm process in Guangdong from 27 August to 1 September 2018. Using the physical decomposition method indicates that the monsoon depression and the low-level jet can provide sufficient amount of water vapor and energy for the rainstorm process. The location of the zero line of the entropy change corresponds well with the spatial distribution of the precipitation. Energy accumulating at the zero line of the entropy change is favorable to the development of the rainstorm. To further verify the influence of the monsoon depression, sensitivity experiments are constructed. Sensitivity experiments were conducted by filtering out the perturbation component in the monsoon depression to change the intensity of the monsoon depression. Results show that when the monsoon depression is strong, the rainstorm is likely to occur and the precipitation is strong. When the monsoon depression is weak, the precipitation is reduced or even absent. The diagnostic analysis shows that the energy helicity has implications for the development of the rainfall. When the energy helicity is greater, the intensity of precipitation is stronger. When the intensity of the monsoon depression weakens, the energy helicity decreases and the precipitation weakens.