Spatial Patterns and Intensity of the Surface Storm Tracks in CMIP5 Models

Booth, James F.; Kwon, Young‐Oh; Ko, Stanley; Small, R. Justin; Msadek, Rym

doi:10.1175/jcli-d-16-0228.1

Cited by 28 publications

(32 citation statements)

References 55 publications

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“…For example, while we find that prescribing the surface temperature in models corrects the simulated trends in SH midlatitude v 0 T 0 , prescribing the surface temperature was also found to improve the agreement between simulated and observed climatology EKE in the NH. 54,55 And, while we see a hemispheric asymmetry in v 0 T 0 trends over recent decades, which disappears by the end of the 21st century ( Figs. 1c, d, and 3c, d), the projected changes in EKE also show hemispherically asymmetric behavior.…”

Section: Discussionmentioning

confidence: 68%

Linking midlatitudes eddy heat flux trends and polar amplification

Chemke

Polvani

2020

npj Clim Atmos Sci

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Eddy heat fluxes play the important role of transferring heat from low to high latitudes, thus affecting midlatitude climate. The recent and projected polar warming, and its effects on the meridional temperature gradients, suggests a possible weakening of eddy heat fluxes. We here examine this question in reanalyses and state-of-the-art global climate models. In the Northern Hemisphere we find that the eddy heat flux has robustly weakened over the last four decades. We further show that this weakening emerged from the internal variability around the year 2000, and we attribute it to increasing greenhouse gases. In contrast, in the Southern Hemisphere we find that the eddy heat flux has robustly strengthened, and we link this strengthening to the recent multidecadal cooling of Southern-Ocean surface temperatures. The inability of state-of-the-art climate models to simulate such cooling prevents them from capturing the observed Southern Hemisphere strengthening of the eddy heat flux. This discrepancy between models and reanalyses provides a clear example of how model biases in polar regions can affect the midlatitude climate.npj Climate and Atmospheric Science (2020) 3:8 ; https://doi.

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Section: Discussionmentioning

confidence: 68%

Linking midlatitudes eddy heat flux trends and polar amplification

Chemke

Polvani

2020

npj Clim Atmos Sci

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“…Achieving this goal is, however, hampered by the region-specific nature of the circulation features that control weather in different parts of the globe. Global-scale analyses are usually confined to assessing a particular aspect of the atmospheric circulation, for example surface storm tracks (Booth et al 2017), whereas regional-scale analyses that target multiple circulation features, for example those based on circulation pattern classifications, are usually only conducted for a particular region, for example Europe (Otero et al 2017, Stryhal andHuth 2018) or North America (Prein et al 2019). From a methodological standpoint, the current study bridges these two evaluation philosophies by assessing atmospheric circulation biases in GCMs over 6 continental-scale regions -roughly corresponding to major CORDEX domains-covering the inhabited terrestrial areas of the globe.…”

Section: Introductionmentioning

confidence: 99%

Reductions in daily continental-scale atmospheric circulation biases between generations of global climate models: CMIP5 to CMIP6

Cannon

2020

Environ. Res. Lett.

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This study evaluates and compares historical simulations of daily sea-level pressure circulation types over 6 continental-scale regions (North America, South America, Europe, Africa, East Asia, and Australasia) by 15 pairs of global climate models from modeling centers that contributed to both Coupled Model Intercomparison Project Phase 5 (CMIP5) and CMIP6. Atmospheric circulation classifications are constructed using two different methodologies applied to two reanalyses. Substantial improvements in performance, taking into account internal variability, are found between CMIP5 and CMIP6 for both frequency (24% reduction in global error) and persistence (12% reduction) of circulation types. Improvements between generations are robust to different methodological choices and reference datasets. A modest relationship between model resolution and skill is found. While there is large intra-ensemble spread in performance, the best performing models from CMIP6 exhibit levels of skill close to those from the reanalyses. In general, the latest generation of climate models should provide less biased simulations for use in regional dynamical and statistical downscaling efforts than previous generations.

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“…Figure 5 shows the global maps of annual mean wind differences between the ASCAT and ERA products, along with the annual mean wind from ASCAT to aid the interpretation. Note that the spatial error patterns in ERA5 are very similar to those found in ERA Interim, only much reduced in amplitude (close to about 50% in the zonal the ACC, which are typical baroclinic growth regions associated with large meridional SST gradients [Sampe and Xie, 2007] [ Booth et al, 2017]. We note that model wind variability is overall defective in the zonal and meridional components at midlatitudes (red colors in bottom panel of Fig.6), with locally enhanced biases (defect) along the WBCs (i.e., Agulhas Return 30 Current, Brazil Current, Gulf Stream and Kuroshio Extension) and the Antarctic Circumpolar Current (ACC), and particularly biased (defect) meridional variability along the ITCZ in the tropics (coinciding with the maximum mean wind divergence).…”

Section: Ocean Currentsmentioning

confidence: 72%

Characterizing ERA-interim and ERA5 surface wind biases using ASCAT

Rivas¹,

Stoffelen²

2019

Preprint

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Abstract. This paper analyses the differences between ERA-Interim and ERA5 surface winds fields relative to ASCAT ocean vector wind observations, after adjustment for the effects of atmospheric stability and density, using stress equivalent winds (U10S), and air-sea relative motion using ocean current velocities. In terms of instantaneous RMS wind speed agreement, ERA5 winds show a 20 % improvement relative to ERA interim, and a performance similar to that of currently operational ECMWF forecasts. ERA5 also performs better than ERA-interim in terms of mean and transient wind errors, wind divergence and wind stress curl biases. Yet, both ERA products show systematic errors in the partition of the wind kinetic energy into zonal and meridional, mean and transient components. ERA winds are characterized by excessive mean zonal winds (westerlies) with defective mean poleward flows at mid-latitudes, and defective mean meridional winds (trades) in the tropics. ERA stress curl is too cyclonic at mid and high latitudes, with implications for Ekman upwelling estimates, and lack detail in the representation of SST gradient effects (along the equatorial cold tongues and WBC jets) and mesoscale convective airflows (along the ITCZ and the warm flanks for the WBC jets). It is conjectured that large-scale mean wind biases in ERA are related to their lack of high frequency (transient wind) variability, which should be promoting residual meridional circulations in the Ferrell and Hadley cells.

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Spatial Patterns and Intensity of the Surface Storm Tracks in CMIP5 Models

Cited by 28 publications

References 55 publications

Linking midlatitudes eddy heat flux trends and polar amplification

Linking midlatitudes eddy heat flux trends and polar amplification

Reductions in daily continental-scale atmospheric circulation biases between generations of global climate models: CMIP5 to CMIP6

Characterizing ERA-interim and ERA5 surface wind biases using ASCAT

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