Validation of GCM, and the need of High resolution atmospheric and hydrological model Vicente Barros and Mariano Re San José de Costa Rica 28 May 2003

Forcings of the Plata River level Tributarios Vientos Onda de marea

Tributaries: -The Plata basin covers 3. 2 M Tributaries: -The Plata basin covers 3.2 M. Km² - Runoff depends on Precipitation and evaporation (Temperature) - How good are precipitation and temperature scenarios?

Precipitation Climate minus simulated precipitation scenarios

Validation of climate models: precipitation Difference in annual precipitation between HADCM3 experiment and observed data (mm/day) ~ 30% less than observed

Precipitation features (PFs) for 5 x 5 degree boxes Seasonal distribution of during Dec.1997 to Nov.2000 observed by the TRMM Precipitation Radar (E. Zipser, G. Mota, and S. Nesbitt, 2002) For more details about PF definition see Nesbitt et al., 2000, J. Climate, 13, 4087-4106. The results presented by Ed Zipser show us the importance of the Mesoscales Convective system activity in producing precipitation over la Plata Basin. These figures are showing the seasonal distribution of PFs for 5 x 5 degree boxes of lat/lon during Dec.1997 to Nov.2000 observed by the TRMM Precipitation Radar (PR) associated with all types of MCS showing that they are very active over northwestern South America an la Plata Basin area. However , when only the more intense MCS are considered, their activity is maximum over the la Plata Basin all year around but with more activity during the transition seasons MCSs appear to be maintained by the advection of warm moist tropical air via the low-level jets. Evidence was presented showing that the SALLJ was present prior to the onset of convection, with 80% of the MCSs occurring during periods with intense northerly low-level flow. The observed diurnal cycle of MCS activity includes an onset period between 1500-2100 LT, a mature phase at night and a dissipation phase in the morning. The diurnal cycle as identified with observed rainfall and TRMM products in southern South America (south of 15S) shows a nocturnal maximum consistent with that of the MCS activity. In contrast, over most of the Amazon rainfall shows a maximum in early afternoon. There is a need for more observations of rainfall in order to validate TRMM and other satellite-derived precipitation products.

This figures shows that precipitation associated with MCS explain over the la Plata Basin more than 70% of total seasonal precipitation. This conclusion is not too encouraging as models are doing relatively bad predicting those systems. However there is some hope for improvements as Ed also showed that South American LLJ has a key role organizing the Convection. MCSs appear to be maintained by the advection of warm moist tropical air via the low-level jets. Evidence was presented showing that the SALLJ was present prior to the onset of convection, with 80% of the MCSs occurring during periods with intense northerly low-level flow.

850 hPa Circulation Composites - January Warm Events Cold Events

Precipitation is too understimated by GCM: Some physical processes are misrepresented Difficulties with downscaling and Perturbation techniques Hope: CRM models

GCM runned with low resolution Do not resolve Meso Convective Systems Do not represent topography correctly Parameterization of convective activity? Remote ocean forcing? Frequency and intensity of synoptic perturbations?

SST at Niño 3.4 from NCEP-NCAR reanalysis

SST at Niño 3.4 from HadCm3 SRES A2 experiment SST at Niño 3.4 from GFDL SRES A2 experiment

ETA MODEL EXPERIMENT: Domain and features Workstation ETA Adapted by M. Pyle (NOAA) Horizontal resolution: Grid of 1°lat.X 1°long Vertical: 60 levels Time step: 360 s Running in a System CRAY, Origin 2000. 40 processors Experiment: 10 years with NCEP/NCAR Reanalysis

Mean sea level: IPCC Scenarios

Climate Change 2001: Working Group I: The Scientific Basis                                                                                                    Get Javascript   Other reports in this collection Figure 11.12: Global average sea level rise 1990 to 2100 for the SRES scenarios. Table of contents Other reports in this collection                                             

Climate Change 2001: Working Group I: The Scientific Basis                                                                                                    Get Javascript Other reports in this collection Figure 11.13: Sea level change in metres over the 21st century resulting from thermal expansion and ocean circulation changes calculated from AOGCM experiments following the IS92a scenario Table of contents Other reports in this collection                                             

Wind effect on water level is not linear Thus: The mean water level has to be calculated by running the hydrodinamic model forced by instantaneous winds