Moistening processes in the observed and simulated MJOs during DYNAMO/CINDY

Friday, 22 April 2016: 9:30 AM
Miramar 1 & 2 (The Condado Hilton Plaza)
Kai-Chih Tseng, NTU, Taipei, Taiwan; and C. H. Sui

A model simulation is performed to analyze the recharge-discharge mechanism of moisture and moist static energy (MSE) in the Madden Julian oscillations observed over Indian Ocean during Dynamics of Madden Julian Oscillations (DYNAMO) and Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (CINDY2011) using Model for Prediction Across Scales (MPAS). The results of simulation are compared with sounding, operational assimilation and satellite data. The model captured the broad features of two MJOs in terms of wind filed, outgoing long wave radiation and precipitation. The model also simulated hierarchical structure from low-troposphere ascending motion to deep ascending motion in the two MJO events but the model simulated stronger ascent, more active synoptic disturbances and stronger moistening process by advection as revealed in the following budget analysis. The total and scale-separated moisture and MSE budget are calculated by temporal projecting methods (e.g. Tseng et al (2015)). Comparison with reanalysis data in north sounding array, model reasonably captured broad-scale advection by mean-intraseasonal interaction and diabatic process (surface flux and radiative feedback) which are the dominant moisture and MSE sources in suppressed stage and cloud developing stage. Furthermore, we decomposed vertical velocity into deep mode and shallow mode by Empirical Orthogonal Function and the method in Back and Bretherton (2009). The result shows an evolution from suppressed stage shallow mode that destabilized atmosphere by recharging column-integrated MSE to the development of deep mode causing a near balance between radiative cooling and condensation heating. This is being analyzed by a conceptual model of wave dynamics coupling with shallow and deep convection.
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