GC33A-0492:
Downscaling of South America present climate forced by three global models
Wednesday, 17 December 2014
Sin Chan Chou1, André A Lyra1, Gustavo Sueiro1, Caroline F Mourao1, Adan Silva1, Gracielle Chagas1, Jorge L Gomes1, Daniela C Rodrigues1, Isabel Pilotto1, Priscila S Tavares1, Diego A Campos1, Claudine P Dereczynski2, Josiane F Bustamante1 and Diego Chagas3, (1)INPE National Institute for Space Research, Sao Jose dos Campos, Brazil, (2)UFRJ Federal University of Rio de Janeiro, Meteorology, Rio De Janeiro, Brazil, (3)CEMADEN, Cachoeira Paulista, Brazil
Abstract:
The objective of this work is to evaluate the downscaling of three global coupled ocean-atmosphere models by setting up the Regional Climate Model at 20-km resolution over the domain that encompasses South America, Central America and parts of the adjacent oceans. The RCM is the Eta model used at CPTEC since 1997 for weather forecasts, since 2000 for seasonal forecasts and since 2012 for climate change studies. The model has suffered some upgrades and has turn into a finite volume model. Some examples of upgrades are the vertical coordinate refinement, the vertical advection scheme, some physics parameters, etc. To run for the time range of several decades and to synchronize with the global models, the calendar of this version of this model was modified. The global models are: the Hadley Centre model, HadGEM2-ES, the Japanese MIROC5 model, and the Brazilian BESM2.3.1 model. Their resolutions range from about 250 km to about 150 km. The present period simulations started from about 1960 until 2005. This step is the preparation for the future climate change scenarios runs driven by the same global models. Evaluations were based on CRU data. The mean spatial distribution of precipitation and temperature showed agreement against the observations. The simulated precipitation and temperature fields from the Eta showed correct seasonality along the year. The regional model simulations driven by BESM showed the least amount of precipitation over the tropical Pacific and Atlantic oceans, whereas the simulations driven by MIROC5 showed the largest amount in those oceans. The mean seasonal cycle of precipitation for three major regions in Brazil showed underestimate in the Amazon region, but overestimate in Central-South Brazilian region. The mean seasonal cycle of temperature were underestimated along all the year. The frequency distribution of precipitation showed that the regional model reach more intense precipitation rates than the global models, and similarly for temperature extremes. Trends of extreme indicators such as consecutive dry days, total annual precipitation were also calculated and compared against some previous works.
