Extreme cold events in South America analyzed from a GFDL model perspective: comparison between CMIP3 and CMIP5 climate scenarios

ARANEO, DIEGO C.; ARANEO, DIEGO C.; MÜLLER, GABRIELA V.; MÜLLER, GABRIELA V.; REPINALDO, CINTIA R. R.; REPINALDO, CINTIA R. R.

THEORY & APPLICATION CLIMATOLOGY

SPRINGER WIEN

Año: 2017 p. 1 - 14

0177-798X

This paper deals with the future change projections ofextreme cold events in relation to historical climate simulations, based on thecomparison between two versions of the GFDL model, CMIP3 and CMIP5, in threeregions of southeastern South America where these events are frequent. To this end,the compositions of up to five extreme events below zero degrees at 850 hPawere considered. They were derived from daily data collected from May toSeptember of the NCEP/NCAR reanalysis and GFDL Coupled Atmospheric and OceanicGlobal Circulation Model. The study periods run from 1961 to 1990 and from 2081to 2100 for the most critical scenarios: A2 (GFDL-CM2) and RCP8.5 (GFDL-CM3).Sea level pressure, temperature and wind were analyzed at 850 hPa, and windalso at 250 hPa, for each of the areas under study, representing tropical (Area1) and subtropical (Area 2 and Area 3) latitudes.The ability of the model to simulate the historicalclimate, represented by the reanalysis, increased as latitude decreased, CM3version being better for subtropical latitudes than CM2. Depending on GFDLmodel version, temperature were higher or lower than those shown by thereanalysis in the tropical latitudes. In contrast, at subtropical latitudes, bothversions of the model present lower values.An increase in mean temperature is expected in thefuture in the three areas, mainly at tropical latitudes (Area 1) according toboth versions of the model, which is in line with the results reported by otherglobal models. In Area 2, a further increase in temperature is projected in CM3version, while, for Area 3, the greatest projection is in CM2 version.Changes are expected for the future climate, primarilyexplained by the configuration of the circulation fields, such as in the caseof the subtropical areas in CM2, whose pattern is more related to thattypically associated with radiative cooling, rather than the advective coolingshown in the historical climate. This result is in contrast with the results ofthe CM3 version, which displays a pattern associated with cold air advection fromthe south for both the historical and future climate. As regards the tropicalarea, both versions of the model reveal a considerable reduction in the numberof extreme cold events.