332 Heating and Moistening Processes of the MJO in ECMWF Reforecasts

Monday, 23 January 2017
4E (Washington State Convention Center )
Ji-Eun Kim, University of Miami, Miami, FL; and C. Zhang, G. Kiladis, and P. Bechtold

The quadrilateral sounding array measurements during the Dynamics of the Madden-Julian Oscillation (DYNAMO) field campaign have provided a unique opportunity to assess heating and moistening processes of the Madden-Julian Oscillation (MJO) initiation/propagation over the Indian Ocean. The estimated apparent heat source and moisture sink based on the observations, however, still do not provide enough information for the complete analyses of heat and moisture budgets. To address this limitation, we use ECMWF Integrated Forecasting System (IFS) reforecast data to study detailed contributions of physical and dynamical processes to the total Lagrangian and local heating and moistening associated with the MJO during the DYNAMO period over an extended region of the tropics. The IFS reforecasts reasonably represent the key features of circulation, heating, and moistening with some uncertainty due to smaller-scale flux terms that cannot be captured in observation-derived values. The reforecast data show that convection is responsible for the greatest contribution to both the apparent heat source and moisture sink, followed by cloud microphysics. Except for spurious signals near the surface, vertical diffusion and gravity wave drag provide negligible contributions. Although radiative cooling exists for the most of time below the upper troposphere, reduced cooling (anomalous radiative heating) in the lower and upper troposphere precedes deep convection that is also accompanied by anomalous radiative heating, suggesting the likely role of radiation in the progression of the MJO. While overall there is a dry bias in the local moisture tendency calculated by the physical and dynamical terms in the IFS forecasts, anomalies of the local tendency generally capture moistening in the developing phase and drying in the decaying phase, highlighting the utility of reforecast data in studying MJO processes.
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