@Article{LiebmannCSMCAFV:2007:OnEnRa,
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
(INPE/CPTEC)}",
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 = "24 abr. 2024"
}