Monday, 23 January 2017
4E (Washington State Convention Center )
Previous idealized studies have shown that radiative feedbacks aggregate convection into large cloud clusters over Tropical Oceans in an atmosphere under radiative convective equilibrium. In this work, cloud permitting model simulations from the Model for Prediction Across Scales-Atmosphere (MPAS-A) are used to examine the effect of the radiative feedbacks on the size distribution of cloud populations at different phases of the Madden-Julian Oscillation (MJO), which is reproduced more realistically compared to simulations that rely on convective parameterizations. The high-resolution (4 km grid spacing) region of the global model covers the equatorial Indian Ocean while the resolution gradually decreases to 32 km grid spacing elsewhere. The initiation and eastward propagation of the November 2011 episode of MJO is selected for a case study. The cloud populations simulated by the model are extensively evaluated against measurements from AMIE/DYNAMO/CINDY field campaign and satellite observations. In the sensitivity experiment shortwave and longwave radiative heating from moisture and clouds are selectively turned off. The impacts of radiative heating on the cloud size distributions within the MJO convection envelope and the overall propagation characteristics of the simulated MJO episode are examined.
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