Comparison of Model Simulated and Observed Ocean Feedback during Dynamics of the Madden-Julian Oscillation (DYNAMO)

The evolution of air-sea interaction during the initiation phase of the MJO in the Indian Ocean is investigated in this study. Numerical simulations of the MJO from the fully coupled air-ocean-wave Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®1) suggests a see-saw process of heat storage and release of energy by the ocean before and during the MJO may be important for the propagation of MJO in the Indian Ocean. We compare the COAMPS real-time DYNAMO model forecasts to the near sea surface measurements obtained from the NOAA Earth System Research Laboratory's Flux Tower on board the Research Vessel Revelle. Four months of model-observation comparisons between September and December 2011 reveal that a tightly coupled atmosphere and ocean system exists at the equator on the MJO time scale. We will discuss the similarity and differences of three MJO episodes captured during this period by COAMPS and the Flux Tower. Our preliminary results show COAMPS bulk SST predictions were generally good. However, the lack of skin SST parameterizations in COAMPS and deficiency of ocean mixing of the warm layer had noticeable effects on the magnitude and timing of upper-ocean heat storage and release on subsequent model simulated convection. In contrast to the suppressed phase, the convective phase of MJO COAMPS simulations shows a rapid transition of low-level winds from weak easterly flow to a strong westerly wind burst. The ocean's response to this wind change was evident in the enhancement of equatorial Wyrtki jet and turbulent mixing through the mixed layer. Results from the uncoupled COAMPS simulations will be presented to quantify the role of air-sea interaction as well as the ramification for future air-sea interaction physics improvements for medium range forecasts.