Observation of jet stream winds during NAWDEX and characterization of systematic meteorological analysis errors

Schäfler, A., Harvey, B. ORCID: https://orcid.org/0000-0002-6510-8181, Methven, J. ORCID: https://orcid.org/0000-0002-7636-6872, Doyle, J. D., Rahm, S., Reitebuch, O., Weiler, F. and Witschas, B. (2020) Observation of jet stream winds during NAWDEX and characterization of systematic meteorological analysis errors. Monthly Weather Review, 148 (7). pp. 2889-2907. ISSN 0027-0644 doi: 10.1175/MWR-D-19-0229.1

Abstract/Summary

Observations across the North Atlantic jet stream with high vertical resolution are used to explore the structure of the jet stream, including the sharpness of vertical wind shear changes across the tropopause and the wind speed. Data was obtained during the North Atlantic Waveguide and Downstream impact EXperiment (NAWDEX) by an airborne Doppler wind lidar, dropsondes and a ground-based Stratosphere-Troposphere radar. During the campaign small wind speed biases throughout the troposphere and lower stratosphere of only -0.41 m s-1 and -0.15 m s-1 are found respectively in the ECMWF and UK Met Office analyses and short-term forecasts. However, this study finds large and spatially coherent wind errors up to ±10 m s-1 for individual cases, with the strongest errors occurring above the tropopause in upper-level ridges. ECMWF and Met Office analyses indicate similar spatial structures in wind errors, even though their forecast models and data assimilation schemes differ greatly. The assimilation of operational observational data brings the analyses closer to the independent verifying observations but it cannot fully compensate the forecast error. Models tend to underestimate the peak jet stream wind, the vertical wind shear (by a factor of 2-5) and the abruptness of the change in wind shear across the tropopause, which is a major contribution to the meridional potential vorticity gradient. The differences are large enough to influence forecasts of Rossby wave disturbances to the jet stream with an anticipated effect on weather forecast skill even on large scales.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/90608
Item Type	Article
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > NCAS Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	American Meteorological Society
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