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Comparison of Structure and Evolution Characteristics of Boreal Summer and Winter Intraseasonal Oscillations Derived from Reanalysis Products and Satellite observations

The proposed project is to evaluate the performance of various latest reanalysis products in capturing the MJO 3D structures, particularly its vertical heating and humidity profiles, and MJO multi-scale characteristics and initiation processes. The reanalysis products to be evaluated include the NCEP Climate Forecast System (CFS) Reanalysis, the ESRL 100-year Historical Reanalysis, NASA MERRA, ERA-interim, and JMA reanalysis. Available observations from recently available satellite products and planned field campaigns will be used to validate the reanalysis products. 

Firstly, we will diagnose and compare the 3D dynamic and thermodynamic structures at various phases of the MJO. Because of distinctive seasonal evolution characteristics, we will separate the boreal winter (November-April) and summer (May- October) seasons. We will examine the horizontal and vertical profiles of specific humidity and its relationships with MJO convection, vorticity, divergence, vertical motion, surface fluxes, SST, CAPE, and other dynamic and thermodynamic variables. A key variable to examine is the heating field. Daily 3D fields of apparent heating (Q1; Yanai et al. 1973) derived from the above reanalysis datasets will be compared with each other, and validated against TRMM estimate based on the “Trained” Radiometer Heating (TRAIN), Convective-Stratiform Heating (CSH), and Spectral Latent Heating (SLH) algorithms. We will evaluate the evolution of the heating profiles associated with shallow (congestus) convection, deep convection and stratiform clouds.

Secondly, we will evaluate and compare the multi-scale characteristics of the MJO in both the boreal winter and summer seasons. A focus will be on the structure and evolution of higher-frequency perturbations and their MJO-phase-dependent feature. A spatial-temporal wavelet transform method will be applied to separate higher frequency modes. The possible upscale feedback of higher-frequency perturbations to MJO will be examined with a new diagnostic strategy that separates the eddy interaction with ISO and slowly varying background mean flows. In addition, we will reveal the common features associated with the MJO initiation in the western equatorial Indian Ocean based on the diagnosis of the reanalysis products.

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