Vertical Wind Characteristics in Precipitating Cloud Systems over West Sumatera, Indonesia, Observed with Equatorial Atmosphere Radar: Case Study of 23-24 April 2004 during the First CPEA Campaign Period

Abstract

Characteristics of vertical wind profiles (VWPs) in precipitating clouds were studied over western Sumatera (or Sumatra) Island of the Indonesian maritime continent during the first Coupling Process of Equatorial Atmosphere (CPEA) campaign period (10 April-09 May 2004) using Equatorial Atmosphere Radar (EAR) and X-band Doppler radar (XDR) to examine the dynamic and thermodynamic structures of various types of tropical precipitating systems. VWPs were precisely measured with the EAR directly in precipitating clouds, which were identified using simultaneous XDR observation. A super-cloud cluster (SCC) system of the intraseasonal variation (ISV) onset phase was examined as a case study.
The SCC consisted of three cloud clusters (CCs), which were further partitioned into convective and stratiform cloud regions based on the XDR reflectivity fields. Vertical winds varied greatly in time and height according to variations in the reflectivity fields. Although the VWPs for each CC showed quite scattered variations in time and height, they had significant dependence on the corresponding 10 dBZ radar echo top heights (H_10dBzs). Spectral representations of vertical wind and reflectivity profiles, which were stratified by H_10dBz heights, showed the following distinct characteristics: 1) Convective spectra were divided into two groups by H_10dBz = 10 km. The shorter spectra had massive reflectivity, especially in the lower height with upward currents; the taller spectra had a gentle reflectivity profile with significant upward currents around H_10dBz and apparent downward currents below 8 km in height. 2) Spectra for stratiform clouds were partitioned into three groups by H_10dBz = 6 and 8 km. Beside the shortest group of shallow stratiform clouds, bright band signs were intensified as the H_10dBz increased in the taller two groups. The heights of the maximum upward currents above their bright bands also increased too with the heights of H_10dBz.
The reflectivity spectra and VWPs are discussed in comparison to global precipitation spectra observed by the Tropical Rainfall Measuring Mission (TRMM) satellite and VWPs calculated by rawinsonde sounding array data, respectively.