Coupled Observations and Convectively Induced Air-Sea Interaction in DYNAMO

One of the most challenging problems in predicting MJO initiation over the Indian Ocean is the onset of the large-scale convective activity. Although it has been hypothesized that air-sea interaction is one of the factors affecting the equatorial convective cloud systems, the physical processes through which the convection interacts with the air-sea interface and how they vary in different stages of the MJO have not been clearly identified. The Dynamics of Madden-Julian Oscillation (DYNAMO) field campaign is designed to better understand the physical processes affective cloud population including the environmental water vapor and air-sea fluxes. This study aims to examine the coherent spatial and temporal variability of the air-sea fluxes and convection during the suppressed and active phases of the MJO over the Indian Ocean. More than 200 co-located GPS dropsondes and AXBTs/AXCDTs pairs were deployed from the NOAA WP-3D aircraft during the DYNAMO field campaign from 11 November-13 December 2011, which covers a complete MJO initiation event including both convectively suppressed and active phases. An objective cloud cluster tracking analysis using hourly METEOSAT IR data and satellite derived SST are used in conjunction with the DYNAMO in-situ observations to provide a four-dimensional description of the multi-scale variability of convective cloud systems and the air-sea fluxes in relation to the MJO initiation process including both convective suppressed and active phases over the Indian Ocean. Preliminary results indicate that there are distinct characteristics in both cloud systems and air-sea interaction during the suppressed and active phases. The air-sea temperature difference is about 1 degree larger with higher boundary layer height during the convectively suppressed phase than that of active phase. Convectively induced virtual potential temperature depression is about 4-5 K in a relatively drier and low wind environment, whereas the values are significantly smaller in the active phase. These may have some important implications for the timing of the post-convection surface/boundary layer recovery during an MJO event.