Analysis of MJO Wind-Flux Feedbacks in the Indian Ocean Using Observations

Abstract:

Observations from two Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) buoys along the equator in the Indian Ocean are used to relate surface fluxes and precipitation on intraseasonal timescales. Buoy data are available from 2004 – 2012, though periods of missing data exist. Precipitation measurements are from rain gauges on the buoys, the Tropical Rainfall Measuring Mission (TRMM) and the Global Precipitation Climatology Project (GPCP). The goal of this work is to quantify the relative importance of wind induced surface fluxes, especially latent heat fluxes, to precipitation on intraseasonal timescales. Intraseasonal timescales are isolated in two ways: 1) 20 – 100 day bandpass filtering is applied to the surface flux and precipitation time series and 2) global MJO indices are assigned to each time series. Both methods show a positive relationship between latent heat fluxes and precipitation, where latent heat flux values are about 10% of precipitation values. Precipitation leads latent heat flux variability on the order of a few days. Sensitivity tests and linearization of the latent heat flux formula reveal that wind variability, as opposed to thermodynamic variability, explains most of the intraseasonal latent heat flux variability. This work supports previous studies that indicate wind induced surface fluxes are important to destabilize intraseasonal convection.