Daily cycle of the urban-rural contrast in South America derived from the FPS-SESA multi-model, convection-permitting RCM ensemble

MILOVAC J.; SOLMAN, S.; FERNANDEZ, JESUS; DA ROCHA, R.P.; COPPOLA, E.; RAFFAELE, F; BLAZQUEZ, J; PREIN, A; BETTOLLI MARIA LAURA

Bergen

Workshop; VII Convection Permitting Climate Modelling Workshop; 2023

NCAR-Universidad de Bergen

We demonstrate the poten+al of conven+on-permiEng regional climate models (CPRCMs) tocapture urban-rural contrasts in different variables over large ci+es in South America. We used themul+-model ensemble developed as part of the CORDEX Flagship Pilot Study on ExtremePrecipita+on Events in Southeastern South America (FPS-SESA). It comprises three-year-longcoordinated CPRCM simula+ons centered over subtropical South America at a resolu+on of 4 km.We also included the 4-km-resolu+on simula+on from the NCAR South America Affinity Group,which covers the en+re South American con+nent. Together, these simula+ons form a five-memberensemble consis+ng of two models in different configura+ons (two WRF and three RegCM5members).We assess the ability of this ensemble to capture city footprints in three major South Americanci+es: Buenos Aires, Córdoba, and Porto Alegre. Differences between urban and rural environmentswere computed to iden+fy the urban signal on temperature, referred to as the urban heat island(UHI), rela+ve humidity and wind intensity. The analysis also includes the response of the urbanenvironment to extreme condi+ons such as heat waves. Simulated data have been compared againstobserved hourly sta+on data.CPRCMs successfully captured the UHI signal for the three South American ci+es. The UHI effect wasmost pronounced during nighEme hours with a magnitude of approximately 2ºC. The magnitude ofthis effect was found to be greater in the summer than in the winter. The models also captured thedrier nighEme condi+ons over the ci+es, which may be associated with the UHI effect, althoughthey tended to overes+mate (by up to 10%) the ci+es' drying effect. Addi+onally, the modelsreproduced the observed weaker intensity of the wind over the ci+es, although the magnitude ofthe difference was overes+mated. During heat waves, the CPRCMs were also able to capture theexacerbated warming and