author = "Liebmann, Brant and Camargo, Suzana J. and Seth, Anji and Marengo, 
                         Jos{\'e} Antonio and Carvalho, Leila M. V. and Allured, Dave and 
                         Fu, Rong and Vera, Carolina S.",
          affiliation = "{} and {} and {} and {Instituto Nacional de Pesquisas Espaciais 
                title = "Onset and end of the rainy season in South America in observations 
                         and the ECHAM 4.5 atmospheric general circulation model",
              journal = "Journal of Climate",
                 year = "2007",
               volume = "20",
               number = "10",
                pages = "2037--2050",
                month = "may",
             keywords = "Amazon Basin, tropical atmosphere, preciptiation, rainfall, 
                         climate, variability, convection, monsoon.",
             abstract = "Rainfall in South America as simulated by a 24-ensemble member of 
                         the ECHAM 4.5 atmospheric general circulation model is compared 
                         and contrasted with observations (in areas in which data are 
                         available) for the period 1976-2001. Emphasis is placed on 
                         determining the onset and end of the rainy season, from which its 
                         length and rain rate are determined. It is shown that over large 
                         parts of the domain the onset and ending dates are well simulated 
                         by the model, with biases of less than 10 days. There is a 
                         tendency for model onset to occur early and ending to occur late, 
                         resulting in a simulated rainy season that is on average too long 
                         in many areas. The model wet season rain rate also tends to be 
                         larger than observed. To estimate the relative importance of 
                         errors in wet season length and rain rate in determining biases in 
                         the annual total, adjusted totals are computed by substituting 
                         both the observed climatological wet season length and rate for 
                         those of the model. Problems in the rain rate generally are more 
                         important than problems in the length. The wet season length and 
                         rain rate also contribute substantially to interannual variations 
                         in the annual total. These quantities are almost independent, and 
                         it is argued that they are each associated with different 
                         mechanisms. The observed onset dates almost always lie within the 
                         range of onset of the ensemble members, even in the areas with a 
                         large model onset bias. In some areas, though, the model does not 
                         perform well. In southern Brazil the model ensemble average onset 
                         always occurs in summer, whereas the observations show that winter 
                         is often the wettest period. Individual members, however, do 
                         occasionally show a winter rainfall peak. In southern Northeast 
                         Brazil the model has a more distinct rainy season than is 
                         observed. In the northwest Amazon the model annual cycle is 
                         shifted relative to that observed, resulting in a model bias. No 
                         interannual relationship between model and observed onset dates is 
                         expected unless onset in the model and observations has a mutual 
                         relationship with SST anomalies. In part of the near- equatorial 
                         Amazon, there does exist an interannual relationship between onset 
                         dates. Previous studies have shown that in this area there is a 
                         relationship between SST anomalies and variations in seasonal 
                         total rainfall.",
           copyholder = "SID/SCD",
                 issn = "0894-8755",
             language = "en",
           targetfile = "JournalClimi1520-0442-20-10-2037.pdf",
        urlaccessdate = "25 jan. 2021"