Characteristics and spatio-temporal variability of the Amazon River Basin Water Budget

The spatio-temporal variations of the water budget components in the Amazon region are investigated by using a combination of hydrometeorological observations and moisture fluxes derived from the NCEP/NCAR reanalyses, for the period 1970–1999. The key new finding of this study identifies the major differences in the water balance characteristics and variability between the northern and southern parts of the basin. Our results show that there is a seasonality and interannual variability of the water balance that varies across the basin. At interannual time scales, anomalies in the water balance components in the northern Amazon region show relatively stronger links with tropical Pacific interannual variability. Over the entire region, precipitation exceeds evaporation and the basin acts as a sink of moisture (P>E). However, on some occasions the basin can act as a source for moisture (P<E) under extreme conditions, such as those related to deficient rainfall in northern Amazonia during the strong El Niño of 1983. Our estimates of the Amazon region’s water balance do not show a closure of the budget, with an average imbalance of almost 50%, suggesting that some of the moisture that converges in the Amazon region is not accounted for. The imbalance is larger over the southern Amazon region than over the northern region, and it also exhibits interannual variability. Large uncertainties are detected in the evaporation and moisture-convergence fields derived from the reanalyses, and in the case of evaporation it can be as large as 10–20% when compared with the few field observations across the basin. Observed precipitation fields derived from station data and from grid-box products also show some discrepancies due to sampling problems and interpolation techniques. The streamflow observed at the mouth of the river is obtained after corrections on the series observed taken at a gauging site almost 200 km inland. However, variability in the evaporation, moisture convergence, and observed rainfall and runoff matches quite well.

[1]  V. B. Rao,et al.  Annual variation of rainfall over Brazil and water vapor characteristics over South America , 1996 .

[2]  H. Matsuyama.  The water budget in the Amazon river basin during the FGGE period , 1992 .

[3]  J. Foley,et al.  Trends in the hydrologic cycle of the Amazon basin , 1999 .

[4]  R. Dickinson,et al.  The Geophysiology of Amazonia: Vegetation and Climate Interactions. , 1990 .

[5]  L. Molion.  a Climatonomic Study of the Energy and Moisture Fluxes of the Amazonas Basin with Considerations of Deforestation Effects. , 1975 .

[6]  P. Jones,et al.  Representing Twentieth-Century Space-Time Climate Variability. Part II: Development of 1901-96 Monthly Grids of Terrestrial Surface Climate , 2000 .

[7]  Rafael L. Bras,et al.  Precipitation recycling in the Amazon basin , 1994 .

[8]  Sin Chan Chou,et al.  Model characterization of the South American low-level flow during the 1997–1998 spring–summer season , 2000 .

[9]  Yale Mintz,et al.  Climatology of the terrestrial seasonal water cycle , 1985 .

[10]  J. Marengo.  Interdecadal variability and trends of rainfall across the Amazon basin , 2004 .

[11]  E. Takle,et al.  Suppressing Impacts of the Amazonian Deforestation by the Global Circulation Change , 2001 .

[12]  Ning Zeng,et al.  Seasonal cycle and interannual variability in the Amazon hydrologic cycle , 1999 .

[13]  J. Roads,et al.  Large-Scale Aspects of the United States Hydrologic Cycle , 1994 .

[14]  J. Marengo,et al.  Tropical-midlatitude exchange of air masses during summer and winter in South America: climatic aspects and examples of intense events , 2000 .

[15]  J. D. C. Marques,et al.  Cálculo da evapotranspiração real na Bacia Amazônica através do método aerológico , 1980 .

[16]  C. Rosenzweig,et al.  Calculations of river-runoff in the GISS GGM: impact of a new land-surface parameterization and runoff routing model on the hydrology of the Amazon River , 1994 .

[17]  Michael W. Douglas,et al.  The South American low‐level jet east of the Andes during the 1999 LBA‐TRMM and LBA‐WET AMC campaign , 2002 .

[18]  Taikan Oki,et al.  Global atmospheric water balance and runoff from large river basins , 1995 .

[19]  F. Molteni,et al.  Sensitivity of the ECMWF model northern winter climate to model formulation , 1996 .

[20]  Kevin E. Trenberth,et al.  Estimates of Freshwater Discharge from Continents: Latitudinal and Seasonal Variations , 2002 .

[21]  Carlos A. Nobre,et al.  Precipitation distribution over central and western tropical South America , 1990 .

[22]  J. Marengo,et al.  Validation of model improvements for the GISS GCM , 1994 .

[23]  P. Jones,et al.  REPRESENTING TWENTIETH CENTURY SPACE-TIME CLIMATE VARIABILITY. , 1998 .

[24]  V. Barros,et al.  The Hydrologic Cycle of the La Plata Basin in South America , 2002 .

[25]  James J. Hack,et al.  The Dynamical Simulation of the NCAR Community Climate Model Version 3 (CCM3) , 1998 .

[26]  Kevin E. Trenberth,et al.  Evaluation of the atmospheric moisture and hydrological cycle in the NCEP/NCAR reanalyses , 1998 .

[27]  R. Betts,et al.  Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model , 2000, Nature.

[28]  S. Hastenrath,et al.  Trends of upper‐air circulation and water vapour over equatorial South America and adjacent oceans , 1999 .

[29]  J. Marengo,et al.  Interannual Variability of the Rainy Season and Rainfall in the Brazilian Amazon Basin , 2001 .

[30]  W. J. Shuttleworth,et al.  Evaporation from Amazonian rainforest , 1988, Proceedings of the Royal Society of London. Series B. Biological Sciences.

[31]  A. Baumgartner.  The world water balance , 1975 .

[32]  P. Xie,et al.  Global Precipitation: A 17-Year Monthly Analysis Based on Gauge Observations, Satellite Estimates, and Numerical Model Outputs , 1997 .

[33]  Kevin E. Trenberth,et al.  Evaluation of the Global Atmospheric Moisture Budget as Seen from Analyses , 1995 .

[34]  K. Miyakoda,et al.  Feasibility of Seasonal Forecasts Inferred from Multiple GCM Simulations , 1995 .

[35]  Antonio O. Manzi,et al.  Global climatological features in a simulation using the CPTEC-COLA AGCM , 2002 .

[36]  Scott D. Miller,et al.  SEASONALITY OF WATER AND HEAT FLUXES OVER A TROPICAL FOREST IN EASTERN AMAZONIA , 2004 .

[37]  Marcos Heil Costa,et al.  A comparison of precipitation datasets for the Amazon Basin , 1998 .

[38]  K. Mo,et al.  Large-Scale Atmospheric Moisture Transport as Evaluated in the NCEP/NCAR and the NASA/DAO Reanalyses , 1996 .

[39]  M. Kanamitsu,et al.  CSE Water and Energy Budgets in the NCEP–DOE Reanalysis II , 2002 .

[40]  O. Frumento,et al.  The Atmospheric water vapor cycle in South America and the tropospheric circulation , 2000 .

[41]  R. Reynolds,et al.  The NCEP/NCAR 40-Year Reanalysis Project , 1996, Renewable Energy.

[42]  J. Janowiak,et al.  The Global Precipitation Climatology Project (GPCP) combined precipitation dataset , 1997 .

[43]  C. Nobre,et al.  Assessment of regional seasonal rainfall predictability using the CPTEC/COLA atmospheric GCM , 2003 .

[44]  Roy Edwin Oltman,et al.  Reconnaissance investigations of the discharge and water quality of the Amazon River , 1968 .

[45]  B. Choudhury,et al.  Analyzing the discharge regime of a large tropical river through remote sensing, ground-based climatic data, and modeling , 1996, IGARSS '96. 1996 International Geoscience and Remote Sensing Symposium.

[46]  N. Nova,et al.  Estimativa da evapotranspiração na Bacia Amazônica () , 1976 .