Interannual variability of January precipitation over southern South America simulated by a regional climate model

MENÉNDEZ C., CABRÉ M.F., NÚÑEZ M

Baltimore, Maryland, USA

Conferencia; 1 st International CLIVAR Science Conference "Understanding and Predicting our Climate System"; 2004

The performance of a regional model to represent the interannual variability and the diurnal cycle of January precipitation over southern South America, with emphasis on the low-level jet (LLJ) region is assessed. For this end, an ensemble of month-long simulations (Januaryof the 6 years 1996-2001) driven by assimilated lateral boundary conditions and sea surface temperatures from the NCEP reanalysis were conducted. This period is large enough to represent a broad range of climatic conditions including normal, La Niña and El Niño years.We use the Fifth-generation Penn State/NCAR Mesoscale Model (MM5), version 3.5, coupled with the Oregon State University/NCEP Eta Land-Surface Model (Chen andDudhia, 2001). The following main physical parameterisations are employed: Kain-Fritsch (1993) cumulus convection, explicit moisture scheme including simple ice physics (Dudhia, 1989), cloud-radiation (Benjamin and Carlson, 1986) and NCEP Medium-RangeForecast Model planetary boundary layer (Hong and Pan, 1996). Domain extension, horizontal resolution (60 km) and length of the experiment were limited by the computational resources available.