The separation of convective and stratiform precipitation regions of simulated Typhoon Chanchu and its sensitivity to the number concentration of cloud droplets

Abstract

Following a numerical simulation study, we analyze the effect of the parameter of the cloud condensation nuclei concentration (CNP) on Typhoon Chanchu in convective, stratiform, and mixed precipitation areas based on the following three experiments: (1) a control (CTL) experiment using a mesoscale model and the Reisner-2 cloud scheme with the CNP value specified as 100cm-3; (2) a very clean marine (VCM) CNP experiment (CNP=25cm-3); (3) and a severe contamination (SC) CNP experiment (CNP=1000cm-3). We compare and analyze the simulated cloud structure and microphysical processes of the three experiments within the convective, stratiform, and mixed areas. The three precipitating areas are classified based on the ratio of cloud ice content to cloud water content at all precipitating grids proposed by Sui et al. (2007). The results show that the intensities of most microphysical processes are the largest in the convective area and the smallest in the stratiform area. Ice is dominant in the stratiform region and the water hydrometeor is dominant in the convective region. Furthermore, cloud water develops more quickly than cloud ice do in the mixed area. The response of the convective area to a varying CNP is greater than that of the stratiform area, and the mixed area is only slightly sensitive to the CNP. The dominance of cloud microphysical processes related to the growth of water hydrometeors weakens as the CNP increases. © 2012 Elsevier B.V.