Characteristics of diabatic heating associated with mesoscale convective systems over Indian Ocean from radiosonde and GPS radio occultation

Abstract

This study aims to investigate the characteristics of diabatic heating profiles associated with appearances of Mesoscale Convective Systems (MCSs) over Sumatra Island (SI) and Indian Ocean (IO) including the transitional offshore zone (TZ). We define the parameters of eccentricity, cloud lifetime, and cloud coverage from Multi-Functional Transport Satellite (MTSAT) infrared imageries to identify the MCSs. We derive the diabatic heating profiles over SI and IO using radiosonde data collected during Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (CINDY2011) / Dynamics of the Madden Julian Oscillation (DYNAMO) campaign. We also estimate the diabatic heating profiles from the GPS Radio Occultation incorporated with the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data over TZ, where the radiosonde observations were limited. The results show that heating occurred throughout the entire troposphere during the mature stages of MCSs with more variations in the amplitude and maximum heating up to 20 K/day overland. Furthermore, the altitude of maximum heating over SI is lower than that of IO and TZ. Over SI and TZ, profiles of dissipations (postmature) stage are characterized by cooling in the lower altitude and an upward shift of maximum heating. By analyzing vertical velocity profiles, we confirm that cooling (heating) processes are associated with updraft (downdraft) in the cloud systems. In addition, the presence of cooling that occurs in layers close to the surface could indicate the formation of cold pool during the dissipation phase of the MCSs.