Equator-to-pole temperature differences and the extra-tropical storm track responses of the CMIP5 climate models

• Published in: Climate dynamics Vol. 43; no. 5-6; pp. 1171 - 1182
• Main Authors: Harvey, B. J, Shaffrey, L. C, Woollings, T. J
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.09.2014; Springer Berlin Heidelberg; Springer; Springer Nature B.V
• Subjects: Atmospheric temperature; Climate change; Climate models; Climatology; Climatology. Bioclimatology. Climate change; correlated responses; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Environmental aspects; Exact sciences and technology; External geophysics; General circulation models; Geophysics/Geodesy; linear models; Marine; Meteorology; Oceanography; regression analysis; sea level; Storms; Storms, hurricanes, tornadoes, thunderstorms; summer; Temperature; Tropical cyclones; Troposphere; variance; winter; CMIP5; Climate change; Baroclinicity; Storm tracks; Multimodel; Coupled model; Extratropical cyclone; Southern Hemisphere; General circulation models; Latitudinal variation; climate warming; Climate models; digital simulation; trajectory; Climate prediction; Temperature difference; Northern Hemisphere; Severe weather; global change; storms; climate change
• DOI: 10.1007/s00382-013-1883-9
• ISSN: 0930-7575

This paper aims to understand the physical processes causing the large spread in the storm track projections of the CMIP5 climate models. In particular, the relationship between the climate change responses of the storm tracks, as measured by the 2–6 day mean sea level pressure variance, and the equator-to-pole temperature differences at upper- and lower-tropospheric levels is investigated. In the southern hemisphere the responses of the upper- and lower-tropospheric temperature differences are correlated across the models and as a result they share similar associations with the storm track responses. There are large regions in which the storm track responses are correlated with the temperature difference responses, and a simple linear regression model based on the temperature differences at either level captures the spatial pattern of the mean storm track response as well explaining between 30 and 60 % of the inter-model variance of the storm track responses. In the northern hemisphere the responses of the two temperature differences are not significantly correlated and their associations with the storm track responses are more complicated. In summer, the responses of the lower-tropospheric temperature differences dominate the inter-model spread of the storm track responses. In winter, the responses of the upper- and lower-temperature differences both play a role. The results suggest that there is potential to reduce the spread in storm track responses by constraining the relative magnitudes of the warming in the tropical and polar regions.