Simulation of microphysical structure associated with tropical cloud clusters using mesoscale model and comparison with TRMM observations

Abstract

An attempt has been made in the present study to examine the microphysical structure of a non‐squall Tropical Cloud Cluster (TCC). Three‐dimensional model simulations of cloud microphysical structure associated with a non‐squall TCC occurred on 26 October 2005 over the South Bay of Bengal have been carried out. The initial conditions for the model simulations were improved by incorporating upper air radiosonde observations and Indian Mesosphere Stratosphere Troposphere (MST) radar wind observations through analysis nudging. The horizontal and vertical distribution of the cloud hydrometeor fields observed from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) are compared to those simulated by a mesoscale model using a sophisticated microphysical scheme. Substantial differences are noticed in the amounts of cloud microphysical parameters, with simulated values of hydrometeors being higher than TMI retrievals. Spatial distribution of Cloud Liquid Water (CLW) and Rain Water (RNW) from TMI and model simulations correspond well with each other. The cloud microphysical structure during the initial and mature phases of the storm is also investigated. Comparisons of horizontal and vertical reflectivity structure from the TRMM‐Precipitation Radar (PR) and those simulated by the model show reflectivity cores of values greater than 30 dBZ. The TRMM‐PR echo tops are 3–4 km higher than the simulated echo tops. The 24 hr accumulated precipitation from model simulations are then verified with the combined rainfall product from the TRMM observations.

Acknowledgements

The authors are grateful to the Director of the National Atmospheric Research Laboratory (NARL) for providing the MST radar data and the Co‐ordinator of the SVU‐UGC Center for MST radar applications for providing travel support. Thanks are also due to the NCEP/FNL for data provided by the Data Support Section (DSS) of the Scientific Computing Division at NCAR. The authors would like to acknowledge GSFC/NASA for making the TRMM data available in their web site. The first author (SA) would like to thank the Council of Scientific and Industrial Research (CSIR), New Delhi for providing a Research Fellowship.