Moist Static Energy Budget of the MJO during DYNAMO

Abstract

The authors analyze the column-integrated moist static energy budget over the region of the tropical Indian Ocean covered by the sounding array during the Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (CINDY2011)/Dynamics of the Madden–Julian Oscillation (DYNAMO) field experiment in late 2011. The analysis is performed using data from the sounding array complemented by additional observational datasets for surface turbulent fluxes and atmospheric radiative heating. The entire analysis is repeated using the ECMWF Interim Re-Analysis (ERA-Interim). The roles of surface turbulent fluxes, radiative heating, and advection are quantified for the two MJO events that occurred in October and November using the sounding data; a third event in December is also studied in the ERA-Interim data. These results are consistent with the view that the MJO’s moist static energy anomalies grow and are sustained to a significant extent by the radiative feedbacks associated with MJO water vapor and cloud anomalies and that propagation of the MJO is associated with advection of moist static energy. Both horizontal and vertical advection appear to play significant roles in the events studied here. Horizontal advection strongly moistens the atmosphere during the buildup to the active phase of the October event when the low-level winds switch from westerly to easterly. Horizontal advection strongly dries the atmosphere in the wake of the active phases of the November and December events as the westerlies associated with off-equatorial cyclonic gyres bring subtropical dry air into the convective region from the west and north. Vertical advection provides relative moistening ahead of the active phase and drying behind it, associated with an increase of the normalized gross moist stability.

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

“…In more recent findings, Sobel et al (2014) showed vertical advection discharges column MSE at a rate of 10 % -20 % of precipitation at the peak of the CINDY/ DYNAMO (i.e., Cooperative Indian Ocean Experiments on Intraseasonal Variability in the Year 2011; Dynamics of the MJO) field campaign (Yokoi et al 2014;Moum et al 2013). We note that in both Yu et al (1998) and Sobel et al (2014) precipitation was converted to energy units to compute the ratio of MSE discharge from vertical motions associated with convection. If the ratio of surface fluxes to precipitation is a substantial fraction of these values during active MJO events, then the conclusion could be made that surface fluxes are important for maintaining MJO convection as surface fluxes would counteract a large portion of the MSE discharge associated with vertical motions in deep convection areas.…”

Role of Maritime Continent Convection during the Preconditioning Stage of the Madden-Julian Oscillation Observed in CINDY2011/DYNAMO

“…10 of Sobel et al 2014). Intraseasonal zonal moisture advection and moist static energy were accumulated during this period until the low-level wind changed to strong westerly (Nasuno et al 2015;Sobel et al 2014). On the other hand, when MJO3 was activated on December 21, low-level westerly wind became strong over the central Indian Ocean (Fig.…”

“…Low-level zonal wind along the equator was weak during the second half of October of the preconditioning stage to the active phase of MJO1 (Fig. 10 of Sobel et al 2014). Intraseasonal zonal moisture advection and moist static energy were accumulated during this period until the low-level wind changed to strong westerly (Nasuno et al 2015;Sobel et al 2014).…”

“…During CINDY2011/DYNAMO, moistening process and convective build-up were observed over the central Indian Ocean during the preconditioning stage of each MJO (Johnson and Ciesielski 2013;Yoneyama et al 2013;Hagos et al 2014;Sobel et al 2014;de Szoeke et al 2015;Nasuno et al 2015). de Szoeke et al (2015) suggested that the moistening process was not as simple as the recharge process.…”

Assessment of a Satellite-Based Atmospheric Budget Analysis Method Using CINDY2011/DYNAMO/AMIE and TOGA COARE Sounding Array Data

“…On the other hand, the horizontal advection of MSE depends on horizontal moisture gradient in the large-scale environment and could irregularly modulate the thermodynamic variability that otherwise would be controlled by internal convective dynamics. While horizontal advection could play crucial roles in the driving mechanism of the MJO (e.g., Benedict and Randall 2007;Maloney 2009;Sobel et al 2014), the relative magnitude of hori- zontal and vertical advections is dependent on the cycle of variability and the horizontal component is least important at daily time scales (Inoue and Back 2015). Figure 13 shows the breakdown of moisture/MSE convergence into horizontal and vertical advections calculated from the ensemble mean of all CINDY/DYNAMO events.…”