Radar Rainfall estimation during DYNAMO

The DYNAMO/CINDY-2011 (Dynamics of the MJO, Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011) field campaign enabled collection of various radar data in the Indian Ocean to investigate the 3-D evolution of precipitating clouds before, during, and after the MJO in its alleged initiation region, the central equatorial Indian Ocean. Preliminary rainfall time series statistics from dual-polarimetric S-PolKa and single-polarimetric C-band radars across the DYNAMO observational array show considerable disagreement, especially on high rainfall accumulation days. This study seeks to rectify these rainfall discrepancies by deriving new rainfall relationships from 2DVD data at Gan Island for application to the three single-polarimetric C-band radars as well as S-PolKa. These relations are then compared to previous rainfall equations derived during other tropical oceanic field experiments such as MISMO (Indian Ocean) and TOGA-COARE (west Pacific warm pool). For this component of the project we consult 2DVD from Manus Island and other locations. We apply the new and previously derived rainfall relationships to DYNAMO and TOGA COARE radar data to ensure that the new power law rain estimators are valid in both stratiform and convective rainfall. A statistical error analysis is also completed to address whether these new rainfall relationships are significantly different than those used in the past. We hope to address the importance of drop size distribution variability and ice microphysics in explaining the observed rainfall variability. With this work, we can more meaningfully compare DYNAMO/CINDY-2011 rainfall statistics a) between radar sites in this experiment, b) to other coincident atmospheric and oceanographic measurements in this experiment, and c) to other radar rainfall statistics around the globe.