Impact of different atmospheric states on the simulated ocean response to the MJO

Abstract:

The nature of air-sea interaction of MJOs has been demonstrated by both observational and simulation studies. How the MJO associated atmospheric states impact the upper ocean, however, is still under debate. Given that current reanalyses show significant biases in MJO-related intraseasonal atmospheric components such as OLR and precipitation, it is of interest to investigate how these biases can influence our simulation of upper ocean responses. Thus, we utilized a high-resolution ocean model forced with different atmospheric boundary conditions from ERA-interim and ERA-5. To further explore the impact of the temporal resolution of the forcing fields, we forced the ocean model with both hourly and daily ERA-5 variables. Preliminary results suggest that with different reanalyses and different time resolutions, the upper ocean stability can be significantly altered in some locations along the path of the MJO, suggesting the importance of choosing suitable atmospheric forcings. The diurnal shallowing of the mixed layer depth caused by MJO-related changes in upper ocean salinity and temperature, which was observed during the CINDY campaign, is not well captured by the simulations. Therefore, another simulation with higher vertical resolution near the surface (~ upper 10-meter ocean) will be conducted. Whether the near surface fluctuations can be reasonably simulated and how they respond to different MJO events will then be examined. The physical processes controlling the upper ocean responses will also be explored to determine if they feedback to the simulated intraseasonal SST.