In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 21, No. 10 ( 2021-05-18), p. 7451-7472
Abstract:
Abstract. This study quantifies differences among four widely used
atmospheric reanalysis datasets (ERA5, JRA-55, MERRA-2, and CFSR) in their
representation of the dynamical changes induced by springtime polar
stratospheric ozone depletion in the Southern Hemisphere from 1980 to 2001.
The intercomparison is undertaken as part of the SPARC
(Stratosphere–troposphere Processes and their Role in Climate) Reanalysis
Intercomparison Project (S-RIP). The reanalyses are generally in good
agreement in their representation of the strengthening of the lower
stratospheric polar vortex during the austral spring–summer season,
associated with reduced radiative heating due to ozone loss, as well as the
descent of anomalously strong westerly winds into the troposphere during
summer and the subsequent poleward displacement and intensification of the
polar front jet. Differences in the trends in zonal wind between the
reanalyses are generally small compared to the mean trends. The exception is
CFSR, which exhibits greater disagreement compared to the other three
reanalysis datasets, with stronger westerly winds in the lower stratosphere
in spring and a larger poleward displacement of the tropospheric westerly
jet in summer. The dynamical changes associated with the ozone hole are examined by
investigating the momentum budget and then the eddy heat and momentum
fluxes in terms of planetary- and synoptic-scale Rossby wave contributions.
The dynamical changes are consistently represented across the reanalyses
and support our dynamical understanding of the response of the coupled
stratosphere–troposphere system to the ozone hole. Although our results
suggest a high degree of consistency across the four reanalysis datasets in
the representation of these dynamical changes, there are larger differences
in the wave forcing, residual circulation, and eddy propagation changes compared to the zonal wind trends. In particular, there is a noticeable
disparity in these trends in CFSR compared to the other three reanalyses,
while the best agreement is found between ERA5 and JRA-55. Greater
uncertainty in the components of the momentum budget, as opposed to mean
circulation, suggests that the zonal wind is better constrained by the
assimilation of observations compared to the wave forcing, residual
circulation, and eddy momentum and heat fluxes, which are more dependent on
the model-based forecasts that can differ between reanalyses. Looking
forward, however, these findings give us confidence that reanalysis datasets
can be used to assess changes associated with the ongoing recovery of
stratospheric ozone.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-21-7451-2021
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2021
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
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