Intercomparison of Tropospheric and Stratospheric Mesoscale Kinetic Energy Resolved by the High-Resolution Global Reanalysis Datasets

In order to assess the uncertainties of mesoscale signals in the modern global reanalysis datasets, this study presents the first intercomparison of the tropospheric and stratospheric mesoscale kinetic energy and its spectrum over two selected periods of summer and winter events among six leading high-resolution atmospheric reanalysis products, including ERA5, CRA, MERRA2, CFSv2, JRA-55, and ERA-I. As a supplementary reference, the state-of-the-art 9-km global operational numerical weather prediction (NWP) model Integrated Forecast System (abbreviated as IFS-9) from the European Centre for Medium-Range Weather Forecasts (ECMWF) is adopted for comparison. The global distributions of the divergent and rotational energy indicate that the ability of reanalysis datasets to capture mesoscale signals is closely linked to their resolutions, but it is also impacted by other factors such as convective parameterization. The 30-km ERA5 and the 60-km CFSv2 are stronger than the other reanalysis, and CFSv2 is the strongest in the troposphere. The 30-km CRA, as well as the remaining three reanalysis products (i.e., MERRA2, JRA-55, and ERA-I), is comparable to ERA5 in the troposphere, but its signal decays significantly with height, especially into the stratosphere. Although all datasets illustrate conclusive behaviors for the dominance of the rotational kinetic energy in the troposphere, inconsistency can be identified in the stratosphere, where CRA, MERRA2 and ERA-I fail to capture the dominance of the divergent kinetic energy in the other datasets. Furthermore, the spectral analysis reveals that only ERA5 and CFSv2 can reproduce the observed kinetic energy spectrum in the stratosphere with a distinct shift from a steeper slope (~-3) to a shallower slope (~-5/3) like IFS-9. In addition, the relative differences among datasets, which increase dramatically with height, are much larger in the divergent component, compared with the rotational component. Finally, for both divergent and rotational kinetic energy, the extratropics of the winter hemisphere exhibit much stronger correlations between time series of reanalysis datasets than those in the tropics.