J. Climate, 28, 2097-2119.

Regional simulation of the October and November MJO events observed during the CINDY/DYNAMO field campaign at gray zone resolution

Shuguang Wang
Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY.

Adam H. Sobel
Department of Applied Physics and Applied Mathematics, Department of Earth and Environmental Sciences, and Lamont-Doherty Earth Observatory, Columbia University, New York, NY.

Fuqing Zhang, Y. Qiang Sun, and Ying Yue
Department of Meteorology, The Pennsylvania State University

Lei Zhou
State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Hangzhou, China

Abstract

This study investigates the October and November MJO events observed during the CINDY/Dynamo (Dynamics of MJO) field campaign through cloud-permitting numerical simulations. The simulations are compared to multiple observational datasets. The control simulation at 9 km horizontal resolution captures the slow eastward progression of both the October and November MJO events in surface precipitation, outgoing long wave radiation, zonal wind, humidity, and large scale vertical motion. The vertical motion shows weak ascent in the leading edge of the MJO envelope, followed by deep ascent during the peak precipitation stage, and trailed by a broad second- baroclinic-mode structure with ascent in the upper troposphere and descent in the lower troposphere. Both the simulation and the observations also show slow northward propagation components and tropical cyclone-like vortices after the MJO passage. Comparison with synthesized observations from the northern sounding array shows that the model simulates the passage of the two MJO events over the sounding array region well. Analysis of the moist static energy (MSE) budget shows that both advection and diabatic processes (i.e., surface fluxes and radiation) contribute to the development of the positive MSE anomaly in the active phase, but their contributions differ in by how much they lead the precipitation peak. In comparison to the observational data sets used here, the model simulation may have a stronger surface feedback and a weaker radiative feedback. The contribution from the total advection on the mesoscale to the moisture and MSE budget are small, although the individual terms (horizontal or vertical) can be significant. Gross moist stability in the simulations (similar to that derived from the observation datasets earlier by Sobel, Wang and Kim, 2014) shows a markedly increase from near zero values to ~ 0.8 during the active phase.