This proposal is submitted to NOAA Climate Project Office Modeling, Analysis, Prediction and Projection (MAPP) Program in Response to Funding Opportunity for FY2011. In this project, we will make efforts to contribute to the MAPP FY2011 theme of Evaluate Recently Developed Reanalysis Projects. The overall goal of this proposed project is to provide quantitative information that may guide us to properly use diabatic heating profiles from the recent reanalysis products: MERRA, CFS-R, and ERA-Interim. We propose to (i) quantify similarities and differences between Q1 (total diabatic heating estimated as a residual of heat budget) and QT (direct output of total diabatic heating) from the reanalyses, (ii) compare Q1 (and QT if they are equivalent) from the reanalyses to Q1 estimated using sounding data from selected field campaign, and (iii) define our current knowledge of diabatic heating profiles and its uncertainties by quantifying the agreement and discrepancies between diabatic heating profiles from the reanalyses. The research will be conducted at CIMAS/RSMAS, University of Miami, addressing CIMAS Theme 1: Climate Variability (Task 3).