Wind Speed, Surface Flux, and Intraseasonal Convection Coupling from CYGNSS Data

Abstract:

The heat transfer between the sea surface and lower atmosphere is a key moisture source for the atmospheric circulation and convection. This study analyzes wind speed and surface latent heat flux anomalies from the Cyclone Global Navigation Satellite System (CYGNSS), aiming to understand the physical mechanisms regulating intraseasonal convection, particularly associated with the Madden-Julian oscillation (MJO). One advantage of CYGNSS compared to other space-based datasets is that it can measure surface wind speed with reduced attenuation by precipitation, thus providing useful information about the air-sea interaction and importance of surface fluxes on the development of convection. Consistent with previous studies from buoys, CYGNSS shows that enhanced MJO precipitation is associated with enhanced wind speed, and associated increases in surface heat fluxes help to support the MJO through their moisture supply. A composite analysis during boreal summer over the eastern north Pacific also supports the idea that wind-induced surface flux is important for MJO maintenance there. These results show that the CYGNSS dataset is a useful tool for improving our understanding of the MJO.