HR: 0800h
AN: A51C-02    [Abstracts]
TI: Assessment of RegCM3 over South America: Summer climatology and precipitation diurnal cycle
AU: Rosmeri, R
EM: rosmerir@model.iag.usp.br
AF: Department of Atmospheric Sciences - USP, Rua do Matao, 1226, Sao Paulo, SP 05508- 090, Brazil
AU: Morales, C
EM: morales@model.iag.usp.br
AF: Department of Atmospheric Sciences - USP, Rua do Matao, 1226, Sao Paulo, SP 05508- 090, Brazil
AU: Cuadra, S
EM: santiago@model.iag.usp.br
AF: Department of Atmospheric Sciences - USP, Rua do Matao, 1226, Sao Paulo, SP 05508- 090, Brazil
AU: * Ambrizzi, T
EM: ambrizzi@model.iag.usp.br
AF: Department of Atmospheric Sciences - USP, Rua do Matao, 1226, Sao Paulo, SP 05508- 090, Brazil
AB: The RegCM3 (Regional Climate Model version 3) results over South America were evaluated during 14 summers, from 1989 to 2002 where the National Centers for Environmental Prediction (NCEP) reanalysis was used as initial and boundary conditions The model horizontal resolution is 50 km with 18 sigma-pressure levels. Due to availability of the observational data set the model climatology was constructed for the period 1989-2000 (12 summers) and the precipitation diurnal cycle from 1998 to 2002 (5 summers). The 12 summers climatology shows that the main climate systems associated to the precipitation (such as the South Atlantic Convergence Zone- ZCAS) and air temperature over South America were well reproduced by the model. Over the entire simulation domain, the seasonal errors were -5 percent for precipitation and a systematic cold bias of -0.9oC was obtained. The interannual variability of the precipitation relative bias was low and the relative bias at each summer was lower than 21 percent, which is within the expected error interval (5-30 percent) for the seasonal precipitation simulated by regional climate models. The temperature seasonal bias also presented low interannual variability and in each summer it does not overcome -1.3 K. The precipitation diurnal cycle observed by TRMM/satellite shows pronounced differences between tropical and extra-tropical parts of South America Some interesting features of the precipitation diurnal cycle were well-simulated by the RegCM3. The best agreement between the simulations and observations, especially the phase, were found over the continental area in the tropics and sub-tropics, which presented afternoon maximum (15:00 to 18:00 UTC) and morning minimum (08:00 to 12:00 UTC) precipitation. The large differences were obtained near the Atlantic and Pacific Oceans and in the northern Argentine. In this last region, the observations indicate a night maximum (03:00 UTC) and a morning (09:00 UTC) precipitation peak, which are probably associated to the presence of mesoscale convective systems in this area. The RegCM3 was not able to simulate neither event.
DE: 3300 ATMOSPHERIC PROCESSES
DE: 3309 Climatology (1616, 1620, 3305, 4215, 8408)
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly