Spectral Latent Heating Retrieval for the Midlatitudes Using GPM DPR. Part I: Construction of Lookup Tables

Quantification of latent heating associated with precipitation at midlatitudes is essential for understanding weather and climate. While the spectral latent heating (SLH) algorithm, which retrieves heating profiles using satelliteborne precipitation radars, has been developed for tropical precipitation, it cannot be applied to midlatitude precipitation because of their different characteristics. In this study, the SLH algorithm for global midlatitude precipitation is developed. In Part I, lookup tables (LUTs) that tie heating profiles to precipitation characteristics are constructed using Local Forecast Model simulations of eight extratropical cyclones around Japan. LUTs are produced for the following six categories: convective, shallow stratiform, downward increasing (DI) deep stratiform, downward decreasing (DD) deep stratiform, SUB0 (where the 08C level is near the surface) deep stratiform, and OTHER. The DD/DI subcategories are added to indicate different characteristics of heating profiles due to the relative positions of the cloud base and the 08C level, as detected by the vertical gradient of precipitation profiles below the 08C level. The precipitation-top height (the maximum precipitation rate P_MAX) serves as an index for LUTs for the convective and shallow stratiform (three deep stratiform and OTHER) types. The height of P_MAX roughly corresponds to the cloud-base height, which is used to separate upper-level heating and lower-level cooling. Condensates outside of precipitating areas are estimated to account for 12% of surface precipitation. Since this effect is not included in the LUTs, we applied a correction using this value to the level 3 SLH version 07 product for midlatitudes, considering the energy budget.