Spectral retrieval of latent heating profiles from TRMM PR data.: Algorithm improvement and heating estimates over tropical ocean regions

The Spectral Latent Heating (SLH) algorithm was developed for the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) in Shige et al. (2004, J. Appl. Meteor.). The method uses PR information [precipitation top height (PTH), precipitation rates at the surface and melting level, and rain type] to select heating profiles from lookup tables. Heating profile lookup tables for the three rain types--convective, shallow stratiform, and anvil rain (deep stratiform with a melting level)—were derived from numerical simulations of tropical cloud systems from the Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean--Atmosphere Response Experiment (COARE) utilizing a cloud-resolving model (CRM). To assess its global application to TRMM PR data, the universality of the lookup tables from the TOGA-COARE simulations is examined in this paper. Heating profiles are reconstructed from CRM-simulated parameters (i.e., PTH, precipitation rates at the surface and melting level, and rain type) and compared to the ``true'' CRM-simulated heating profiles, which are computed directly by the model thermodynamic equation. CRM-simulated data from the GARP Atlantic Tropical Experiment (GATE), South China Sea Monsoon Experiment (SCSMEX) and Kwajelin Experiment (KWAJEX) are used as a consistency check.

The consistency check reveals discrepancies between the SLH-reconstructed and GCE-simulated heating above the melting level in the convective region and at the melting level in the stratiform region due to the COARE table. Discrepancies in the convective region are due to differences in the vertical distribution of deep convective heating due to the relative importance of liquid and ice water processes that varies from case to case. Discrepancies in the stratiform region are due to differences in the level separating upper-level heating and lower-level cooling. Based on these results, improvements were made to the SLH algorithm. Convective heating retrieval is now separated into upper-level heating due to ice processes and lower-level heating due to liquid water processes. In the stratiform region, the heating profile is shifted up or down by matching the melting level in the COARE lookup table with the observed one. Consistency checks indicate the revised SLH algorithm performs much better for both the convective and stratiform components than the original one.

The revised SLH algorithm was applied to PR data, and the results compared to heating profiles derived diagnostically from SCSMEX sounding data. Key features of the vertical profiles agree well, particularly the level of maximum heating. The revised SLH algorithm was also applied to PR data for February 1998 and February 1999. The results are compared to heating profiles derived by the convective-stratiform heating (CSH) algorithm. Because observed information on precipitation depth is used in addition to precipitation type and intensity, differences between shallow and deep convection are more distinct in the SLH algorithm compared to the CSH algorithm.