Global atmospheric reanalyses serve as fundamental data sources for weather and climate research, yet their capability to represent mesoscale motions remains subject to substantial uncertainties arising from differences in model resolution, parameterization schemes, and data assimilation systems. To overcome the limitations of previous evaluations that focused primarily on large scales or single variables, this study establishes a multivariate, latitude‑band‑resolved assessment framework that encompasses five modern high‑resolution reanalysis datasets: ERA5, MERRA2, CFSv2, ERA-I, and the newly released JRA-3Q. Using the control forecast of the ECMWF high‑resolution Integrated Forecasting System (IFS at 9‑km grid spacing) as a reference, two typical forcing episodes, a winter cold‑surge event and a summer heavy‑rainfall event, are selected. From the troposphere to the stratosphere, six categories of mesoscale energy are computed: total energy, horizontal kinetic energy (further decomposed into divergent and rotational components), vertical kinetic energy, and potential energy. A novel Normalized Uncertainty Index (NUI) is introduced to enable unified quantitative comparisons across physical quantities of different dimensions and signals at different altitude levels.
Preliminary results demonstrate that the five state‑of‑the‑art reanalyses exhibit systematic and substantial inter‑dataset differences in mesoscale energy spectra, spectral slopes, and gravity‑wave momentum fluxes. These uncertainties are strongly modulated by latitude, altitude, and horizontal wavelength, the largest spread occurs in the tropical lower stratosphere, while the midlatitude troposphere exhibits comparatively smaller inter‑dataset differences. The NUI exhibits a pronounced latitudinal dependence, with the largest spread occurring in the tropics and the smallest in the midlatitudes. Vertically, the discrepancies are relatively modest in the troposphere but become substantially larger in the stratosphere, suggesting that the representation of stratospheric mesoscale dynamics is more sensitive to model configurations than that of tropospheric processes. Furthermore, the NUI increases systematically as horizontal scale decreases, with the most pronounced uncertainties found in the mesoscale band, indicating that current reanalyses diverge most severely in resolving the smaller‑end mesoscale motions. This work provides the panoramic mesoscale evaluation system spanning from the troposphere to the stratosphere and from winter to summer conditions, offering diagnostic benchmarks for improving gravity‑wave and convection parameterizations in global models.


Reference:
Yang, Yufei, Kelin Li, Junhong Wei, and Xinghua Bao, 2026: A Standardized Assessment of Mesoscale Atmospheric Motion Discrepancies in Modern Global Reanalysis Datasets. (manuscript in preparation)
 

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