Evaluation of Improvements in MERRA's Representation of Clouds and Radiation between Version 1 and Version 2

The radiative energy budget provides the chief constraint on the Earth’s climate system.  It is therefore imperative to have an accurate representation of the propagation and deposition of radiative energy within that system.  Reanalysis products have been used in numerous climate studies to examine the state of and processes within the Earth system.  Such studies are of little use if the reanalysis data they are based upon is inaccurate.

NASA’s Global Modeling and Assimilation Office has recently released a new version of the Modern Era Retrospective-analysis for Research and Applications or MERRA.  This presentation describes an evaluation of the energy budget in MERRA-2 from the top of the atmosphere to the Earth’s surface with reference to MERRA-1 and satellite data products. Radiative fluxes at the top of the atmosphere and surface from both MERRA-1 and MERRA-2 have been compared to those from the CERES Energy Balanced and Filled flux product.  Cloud properties and radiative effects were then examined to identify possible causes of observed differences.  The evaluation was extended to include deposition of radiative energy within the atmosphere using comparisons to vertically resolved fluxes from the CERES-CALIPSO-CloudSat_MODIS (C3M) product produced by the CERES team.  The C3M combines retrievals of cloud, aerosol, and other properties from CALIPSO, CloudSat, and MODIS measurements to estimate the properties of the atmospheric column along the Aqua orbit track, then computes radiative fluxes from these estimates.  This vertically resolved data set was used to evaluate the MERRA-2 heating rates, which are important to studies of cloud and aerosol processes.  This presentation discusses the results of this evaluation with a specific focus on differences between MERRA-1 and MERRA-2.