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

• Published in: Geophysical research letters 2020-11, Vol.47 (21), p.n/a
• Main Authors: Bui, Hien X., Maloney, Eric D., Riley Dellaripa, Emily M., Singh, Bohar
• Format: Article
• Language: English
• Subjects: Anomalies; Attenuation; Buoys; Convection; Cyclones; Energy budget; Evaporation; Fluctuations; Global navigation satellite system; Heat; Heat flux; Heat transfer; Latent heat; Latent heat flux; Madden-Julian oscillation; Maintenance; Moist static energy; Navigation; Navigation satellites; Navigation systems; Navigational satellites; Northern Hemisphere; Precipitation; Precipitation anomalies; Summer; Surface fluxes; Surface wind; Wind; Wind speed
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL090376

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). An advantage of CYGNSS compared to other space‐based data sets is that its surface wind speed retrievals have reduced attenuation by precipitation, thus providing improved information about the importance of wind‐induced surface fluxes for the maintenance of convection. Consistent with previous studies from buoys, CYGNSS shows that enhanced MJO precipitation is associated with enhanced wind speeds, and that associated surface heat flux anomalies have a magnitude about 7–12% of precipitation anomalies. Thus, latent heat flux anomalies are an important maintenance mechanism for MJO convection through the column moist static energy budget. 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. Plain Language Summary Enhanced surface evaporation (equivalent to a term called latent heat flux) during high wind speed periods can support precipitation through atmospheric moistening. Such evaporation anomalies form a key air‐sea interaction component of the Madden‐Julian oscillation (MJO). Based on the wind speed and related evaporation anomalies derived from Cyclone Global Navigation Satellite System (CYGNSS) measurements, we show that (1) enhanced MJO precipitation is associated with enhanced wind speed and surface evaporation that may help support the MJO in the Indo‐Pacific warm pool and (2) enhanced local surface evaporation is important for maintenance of the MJO over the eastern north Pacific during Northern Hemisphere summer. These results verify results from previous buoy studies that suggest the importance of enhanced wind‐driven surface evaporation for maintaining the MJO. Key Points CYGNSS wind speed and latent heat flux are used to quantify the feedback of wind‐induced surface fluxes on MJO convection Enhanced MJO precipitation is associated with enhanced wind speed and latent heat anomalies that are about 7–12% of precipitation anomalies The wind‐induced surface flux feedback is also important for MJO convection during the boreal summer in the eastern north Pacific