1. 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

2. Forcings of the Plata River level
Tributarios
Vientos
Onda de marea

3. 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?

4. Precipitation
Climate minus
simulated
precipitation
scenarios

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

6. 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,
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 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.

7. 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.

8. 850 hPa Circulation Composites - January
Warm Events
Cold Events

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

10. 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?

11. SST at Niño 3.4 from NCEP-NCAR reanalysis

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

13. 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

14. Mean sea level: IPCC Scenarios

15. Climate Change 2001: Working Group I: The Scientific Basis
      
    
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Figure 11.12: Global average sea level rise 1990 to 2100 for the SRES scenarios.
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16. Climate Change 2001: Working Group I: The Scientific Basis
      
    
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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
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17. 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