Downscaling of South America present climate driven by 4-member HadCM3 runs
Abstract
皇冠体育app objective of this work is to evaluate climate simulations over South America using the regional Eta Model driven by four members of an ensemble of the UK Met Office Hadley Centre HadCM3 global model. 皇冠体育app Eta Model has been modified with the purpose of performing long-term decadal integrations and has shown to reproduce 鈥減resent climate鈥� - the period 1961鈥�1990 - reasonably well when forced by HadCM3. 皇冠体育app global model lateral conditions with a resolution of 2.5掳 latitude 脳 3.75掳 longitude were provided at a frequency of 6 h. Each member of the global model ensemble has a different climate sensitivity, and the four members were selected to span the range of uncertainty encompassed by the ensemble. 皇冠体育app Eta Model nested in the HadCM3 global model was configured with 40-km horizontal resolution and 38 layers in the vertical. No large-scale internal nudging was applied. Results are shown for austral summer and winter at present climate defined as 1961鈥�90. 皇冠体育app upper and low-level circulation patterns produced by the Eta-CPTEC/HadCM3 experiment set-up show good agreement with reanalysis data and the mean precipitation and temperature with CRU observation data. 皇冠体育app spread in the downscaled mean precipitation and temperature is small when compared against model errors. On the other hand, the benefits in using an ensemble is clear in the improved representation of the seasonal cycle by the ensemble mean over any one realization. El Ni帽o and La Ni帽a years were identified in the HadCM3 member runs based on the NOAA Climate Prediction Center criterion of sea surface temperature anomalies in the Ni帽o 3.4 area. 皇冠体育app frequency of the El Ni帽o and La Ni帽a events in the studied period is underestimated by HadCM3. 皇冠体育app precipitation and temperature anomalies typical of these events are reproduced by most of the Eta-CPTEC/HadCM3 ensemble, although small displacements of the positions of the anomalies occur. This experiment configuration is the first step on the implementation of Eta-CPTEC/HadCM3 upcoming experiments on climate change studies that are discussed in a companion paper.
Citation
Chou, S.C.; Marengo, J.A.; Lyra, A.A.; Sueiro, G.; Pesquero, J.F.; Alves, L.M.; Kay, G.; Betts, R.; Chagas, D.J.; Gomes, J.L.; Bustamante, J.F.; Tavares, P. Downscaling of South America present climate driven by 4-member HadCM3 runs. Climate Dynamics (2012) 38 (3-4) 635-653. [DOI: 10.1007/s00382-011-1002-8]