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The Impact of Split and Displacement Sudden Stratospheric Warmings on the Troposphere
Author(s) -
White Ian P.,
Garfinkel Chaim I.,
Cohen Judah,
Jucker Martin,
Rao Jian
Publication year - 2021
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2020jd033989
Subject(s) - troposphere , wavenumber , stratosphere , barotropic fluid , atmospheric sciences , climatology , sudden stratospheric warming , environmental science , polar vortex , geology , physics , optics
Although sudden stratospheric warmings (SSWs) can improve subseasonal‐to‐seasonal forecasts, it is unclear whether the two types of SSW ‐ displacements and splits ‐ have different near‐surface effects. To examine the longer‐term (i.e., multi‐week lead) tropospheric response to displacements and splits, we utilize an intermediate‐complexity model and impose wave‐1 and wave‐2 stratospheric heating perturbations spun‐off from a control run. At longer lags, the tropospheric response is found to be insensitive to both the wavenumber and location of the imposed heating, in agreement with freely evolving displacements and splits identified in the control run. At shorter lags, however, large differences are found between displacements and splits in both the control run and the different wavenumber‐forced events. In particular, in the control run, the free‐running splits have an immediate barotropic response throughout the stratosphere and troposphere whereas displacements take 1–2 weeks before a near‐surface response becomes evident. Interestingly, this barotropic response found during CTRL splits is not captured by the barotropically forced wave‐2 events, indicating that the zonal‐mean tropospheric circulation is somehow coupled with the generation of the wave‐2 splits. It is also found that in the control run, displacements yield stronger Polar‐Cap temperature anomalies than splits, yet both still yield similar magnitude tropospheric responses. Hence, the strength of the stratospheric warming is not the only governing factor in the surface response. Overall, SSW classification based on vortex morphology may be useful for subseasonal but not seasonal tropospheric prediction.

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