Centro de Previsão de Tempo e Estudos Climáticos (CPTEC/INPE) São Paulo, Brazil ( Integrated observed and modeled atmospheric water budget in the Amazon Basin: How much more can we ask from it? Jose A. Marengo, Carlos Nobre, Helio Camargo, Luiz Candido, Christopher Castro CPTEC/INPE Sao Paulo, Brazil

Moisture transport from the tropical Atlantic Evapotranspiration Rainfall Runoff to Atlantic Ocean Water balance in the Amazon Basin (perfect!)

Water-Balance Approach (1) Terrestrial water balance: Atmospheric water balance: Combined water balance: measured streamflow (R s +R g )

Water-Balance Approach (2) Assumptions: –The contributions of the liquid and solid phases of atmospheric water are negligible –The measured streamflow includes both the contributions of surface and groundwater runoff Limitations: –Atmospheric water balance estimations are accurate only for domains > km2 (Rasmusson 1968, Yeh et al. 1998

Water-Balance Approach (3) Changes in terrestrial water storage (dS/dt) in a given river basin can be estimated as the sum of three terms: : Convergence of the vertically integrated water vapour flux : Change in column storage of water vapour : Evaporation (Latent Heat flux) Reanalysis Data (NCEP) E : Measured rainfall and streamflowObservations P, R

A DJF-CMAP B DJF-CRU C DJF-NCEP D MAM-CMAP E MAM-CRU FR MAM-NCEP Precipitation (mm/day)

E JJA C MAM B NDJ A SON Evaporation (mm/day)

A SON B DJF E JJA C MAM Moisture convergence (mm/day)

Centro de Previsão de Tempo e Estudos Climáticos (CPTEC/INPE) São Paulo, Brazil ( Northeast Trades ET Amazonia Energy balance MCS La Plata Basin wind Ta Td LLJ N hPa Altiplano Moisture flux from Amazonia The Low Level Jet east of the Andes (LLJ) Transports moisture from Amazonia to the Parana La Plata Basin (Marengo et al. 2004)

Water budget the entire Amazon basin (using various rainfall data sets) ComponentGHCNCMAPGPCPNCEPLWCRU Marengo (2004) P E4.3 R2.9 C1.4 P-E P-E-C

Climatological water budget Component MeanEl Niño 1982/83 El Nino 1997/98 La Niña 1988/89 P E R C P-E P-E-C Imbalance=[((C/R)- 1)] 51%38%52%6% Compo nent N. Amazon 1982/ / /89S. Amazon 1982/831997/ /8 9 P E C P-E P-E-C

MediumPredictability Low Predictability Higher predictability LBA PLATIN Seasonal climate predictability in South America MONSOON Medium predictability

Water balance (mm/day) in the Amazon River Basin CPTEC COLA AGCMNCEP Rean+Obsv

Energy balance (W/m2) in the Amazon River Basin CPTEC-COLA AGCM NCEP Rean+OBSV

CPTECNCEP Runoff Precipitation

Evaporation (Latent heat) Sensible Heat

NCEP-CPTEC NCEP-CRU Observed vs modelled precipitation

Conclusions- Imbalances in the water balance (1) Major differences in the behavior of the water balance between the northern and southern parts of the basin (seasonal to interannual variability) In present climates the entire basin behaves as a sink of moisture, while apparently northern Amazonia can act as a net source for moisture under extreme dry conditions (e.g. the strong 1983 El Niño event)  In the future it will become source of moisture (HadCM3) Uncertainties in P in Amazonia, especially in the southern section can reach up to +1.0 mm/day. Some differences among rainfall data sets can reach up to 30% in rainfall and 15% in runoff. Estimates show a basin-wide imbalance of 51%, exhibiting an interannual variability. The choice of rainfall data set also has an impact in the imbalance in the water budget. Thus, significant uncertainties exist in these results and they are sensitive to the data used, in particular the atmospheric can hydrological data. CPTC AGCM underestimates P, R, E, overestimates H

Conclusions- Imbalances in the water balance (2) The accuracy of the computed water balances depends critically on the domain size and on regional characteristics (climate, density of radiosonde data, topography?). The combined water-balance approach is a promising tool for estimating large-scale changes in terrestrial water storage Some limitations: –Domain size needs to be at least > 2*10 5 km2 –Additional validation data would be needed (E from Observations LBA Reference sites?) Aerological estimates of evaporation might be a useful proxy of reality and, when confronted with model evaporation, expose physical parametrization problems (we should take advantage of LBA reference site evaporation data). Nonetheless, the possible applications and uses are numerous given the dearth of observations of terrestrial water storage and its components