Analysis of the impact for PBL turbulent transport for the “21·7” Zhengzhou torrential rainfall

The “21.7” Zhengzhou torrential rainfall is the century’s worst severe storm, characterized by long persistence and intensive 1-hour precipitation. Through comparison analysis of PBL eddy transport for this instantaneous precipitation process, this study tries to investigate the PBL structure and impact of the turbulent diffusion on severe precipitation intensity. Three comparison experiments are designed by tuning coefficients of local eddy diffusion and counter-gradient term. Results show that the PBL turbulent transport has strong influence on severe 1-hour precipitation of “21.7” Zhengzhou torrential rainfall event. It is found through comparison that the decrease of local eddy diffusion noticeably leads to weakening in precipitation intensity and the counter-gradient term chiefly makes some modification on rainfall location and evolution. Furthermore, PBL eddy transport can modulate large-scale atmospheric conditions favorable for heavy storms, such as local water vapor supply and atmospheric instability. Finally, the eddy vapor and heat transport could notably modify the distribution, intensity, evolution of moisture flux convergence and PBL atmospheric instability and exhibit a great influence on this severe storm simulation.