Abstract
The future evolution of storm tracks, their intensity, shape, and location, is an important driver of regional precipitation changes, cyclone-associated weather extremes, and regional climate patterns. For the North Atlantic storm track, Coupled Model Intercomparison Project (CMIP) data indicate a tripole pattern of change under the RCP 8.5 scenario. In this study, the tripole pattern is reproduced by simulating the change of a storm track generated downstream of an idealized sea surface temperature (SST) front under uniform warming on an aquaplanet. The simulated tripole pattern consists of reduced eddy kinetic energy (EKE) upstream and equatorward of the SST front, extended and poleward shifted enhanced EKE downstream of the SST front, and a regionally reduced EKE increase at polar latitudes. In the absence of the idealized SST front, in contrast, the storm track exhibits a poleward shift but no tripole pattern. A detailed analysis of the EKE and eddy available potential energy (EAPE) sources and sinks reveals that the changes are locally driven by changes in baroclinic conversion rather than diabatic processes. However, globally the change in baroclinic conversion averages to zero, thus the observed global EAPE increase results from diabatic generation. In particular, resolved-scale condensation plus parameterized cloud physics dominate the global EAPE increase followed by longwave radiation. Feature-based tracking provides further insight into cyclone life-cycle changes downstream of the SST front. Moderately deepening cyclones deepen less in a warmer climate, while strongly deepening cyclones deepen more. Similarly, the average cyclone becomes less intense in a warmer climate, while the extremely intense cyclones become more intense. Both results hold true for cyclones with genesis in the vicinity of the SST front and elsewhere. The mean cyclone lifetime decreases, while it increases for those cyclones downstream of the SST front. The mean poleward displacement between genesis and maximum intensity increases for the most intense cyclones, while averaged over all cyclones there is a mild reduction and the result depends on the definition of the displacement. Finally, the number of cyclones decreases by approximately 15 %. Aquaplanet simulations with a localized SST front thus provide an enriched picture of storm track dynamics and associated changes with warming.
Highlights
The variability of storm tracks is of paramount importance in understanding regional climate patterns and their change (Shepherd, 2014)
This study examines the response of the storm track downstream of an idealized sea surface tem5 perature (SST) front to uniform global warming by +4 K
The hemisphere on the aquaplanet that includes the idealized SST front successfully reproduces the tripole pattern, which consists of an eddy kinetic energy (EKE) decrease upstream and equatorward of the front, an EKE increase downstream and northeast of the front, and a regional local minimum in the EKE increase at polar latitudes
Summary
The variability of storm tracks is of paramount importance in understanding regional climate patterns and their change (Shepherd, 2014). Individual factors contributing to projected storm track changes have received enhanced consideration in recent years in particular lower and upper-level baroclinicity and increased diabatic processes. The enhanced poleward propagation of extratropical cyclones has been pinpointed as another crucial factor for the poleward shift of the storm tracks (Tamarin-Brodsky and Kaspi, 2017). This is motivated by the fact that increased deepening rates are inherently connected to enhanced poleward motion (Gilet et al, 2009; Coronel et al, 2015; Tamarin and Kaspi, 2016; Besson et al, 2021). Simulations with idealized warming or positive SST anomalies, which are both key ingredients known to intensify cyclone deepening rates, all display an enhanced poleward deflection and shift of the storm tracks, at least for the very intense storms (Palmer and Zhaobo, 1985; Brayshaw et al, 2008; Kodama and Iwasaki, 2009; Graff and LaCasce, 2012; Tamarin and Kaspi, 2017)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
