New Approaches to Understanding the MJO initiation over the Indian Ocean
[13-Dec-2018] Shoup, C.G. and Bulusu, S.
Presented at the 2018 AGU Fall Meeting
The Madden-Julian Oscillation (MJO) is a mode of intraseasonal variability that affects the tropics through air-sea interaction. Anomalous convective and clear-sky conditions associated with the MJO propagate eastward at 3-5 m s-1over the tropical Indian and Pacific Oceans repetitively with a typical period of 40-50 days. Although the MJO was first detected in the zonal wind over the tropical Pacific, its association with many other atmospheric and oceanic properties has been documented. Using salinity to study the MJO is important because it allows for atmospheric conditions to be inferred from the freshwater flux (precipitation minus evaporation) on which SSS is highly dependent. This will be useful in remote regions of the tropics where precipitation measurements may be scarce and in locations where E-P is the dominant mechanism for SSS variability. SSS patterns during the MJO will also allow for surface ocean processes such as advection and upwelling to be inferred as the MJO propagates over a region. Salinity also influences the mixed layer depth, vertical stability, and mixing, which can indirectly alter SST and thus air-sea interaction. In several modeling experiments, the mixed layer has been shown to influence the atmospheric component of the MJO, and therefore salinity may play an important indirect role in this forcing. In this study, we examine how the MJO influences the Sea Surface Salinity (SSS) patterns and explore the processes involved, accounting for seasonal and ENSO dependencies. We investigated if the SSS variations forced by the MJO will be resolved by the Aquarius and Soil Moisture Active Passive (SMAP) salinity missions. These missions will provide the highest spatial and temporal resolutions of SSS on a global scale to date and will enhance our knowledge of many oceanic and atmospheric processes. We used the combination of in situ
(Argo floats salinity data) and remote sensing observations (Aquarius and SMAP salinity), modeling (1/12° Hybrid Coordinate Ocean Model) and reanalysis (Simple Ocean Data Assimilation ocean/sea ice reanalysis; SODA3 reanalysis) to investigate the role of air-sea interactions on the initiation, maintenance, and propagation of the MJO across the tropical Indian and Pacific Oceans.