Moist Static Energy Budget of the MJO during DYNAMO

5 The authors analyze the column-integrated moist static energy budget over the region of 6 the tropical Indian ocean covered by the sounding array during the CINDY/DYNAMO field 7 experiment in late 2011. The analysis is performed using data from the the sounding array 8 complemented by the Objectively Analyzed air-sea Fluxes for the Global Oceans (OAflux) 9 and Clouds and the Earth’s Radiant Energy System (CERES) data for surface turbulent 10 fluxes and atmospheric radiative heating respectively. The analysis is repeated using the 11 ERA Interim Reanalysis for all terms. The roles of surface turbulent fluxes, radiative heat12 ing, and advection are quantified for the two Madden-Julian oscillation (MJO) events that 13 occurred in October and November using the sounding data; a third event in December is 14 also studied in the ERA Interim data. 15 These results are consistent with the view that the MJO’s moist static energy anomalies 16 grow and are sustained to a significant extent by the radiative feedbacks associated with 17 MJO water vapor and cloud anomalies, and that propagation of the MJO is associated 18 with advection of moist static energy. Both horizontal and vertical advection appear to 19 play significant roles in the events studied here. Horizontal advection strongly moistens the 20 atmosphere during the buildup to the active phase of the October event when the low-level 21 winds switch from westerly to easterly. Horizontal advection strongly dries the atmosphere 22 in the wake of the active phases of the November and December events as the westerlies 23 associated with off-equatorial cyclonic gyres bring subtropical dry air into the convective 24 region from the west and north. Vertical advection also provides relative moistening ahead 25 of the active phase and drying behind it, associated with an increase of the normalized gross 26 moist stability. 27