Seasonal cycle and interannual variability in the Amazon hydrologic cycle

An analysis of the Amazon basin hydrologic cycle has been carried out using the NASA/Goddard Earth Observing System (GEOS-1) atmospheric reanalysis, observed rainfall of Xie and Arkin (1996), and historical Amazon River discharge. Over a seasonal cycle the precipitation is found to vary by 5 mm d 21 , and the runoff is found to vary by 2 mm d 21 , while the evaporation largely remains constant. On interannual timescales the hydrologic variability both in the atmosphere and at the land surface is found to be closely related to El Nino-Southern Oscillation (ENSO). The correlation between the Southern Oscillation Index and Xie and Arkin precipitation is 0.8 for the period 1985-1993 and 0.56 for the period 1979 -1996. The precipitation lags behind the Southern Oscillation Index by 3- 4 months while the Amazon River discharge lags behind the precipitation by another 3 months. The lagged relationship suggests interesting dynamic mechanisms. The reanalysis moisture convergence and observed discharge are used to diagnose basin average soil water storage. The year to year variation in the annual mean soil water storage is ;200 mm, comparable to the change within a climatological seasonal cycle. In one case, the basin soil water storage increases by 462 mm from September 1987 to March 1989, suggesting the remarkable ability of the tropical rain forest environment to store and take up water.

[1]  C. Ropelewski,et al.  Global and Regional Scale Precipitation Patterns Associated with the El Niño/Southern Oscillation , 1987 .

[2]  D. Enfield,et al.  Tropical Atlantic sea surface temperature variability and its relation to El Niño‐Southern Oscillation , 1997 .

[3]  E. Davidson,et al.  The role of deep roots in the hydrological and carbon cycles of Amazonian forests and pastures , 1994, Nature.

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

[5]  Dara Entekhabi,et al.  Estimation of Continental Precipitation Recycling. , 1993 .

[6]  Muyin Wang.  Impact of Analysis Uncertainty upon Regional Atmospheric Moisture Flux Budgets: Diagnostic Study and Model Simulation , 1996 .

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

[8]  D. Enfield,et al.  Relationships of inter‐american rainfall to tropical Atlantic and Pacific SST variability , 1996 .

[9]  Andrea Molod,et al.  The climatology of parameterized physical processes in the GEOS-1 GCM and their impact on the GEOS-1 data assimilation system , 1996 .

[10]  C. Justice,et al.  A revised land surface parameterization (SiB2) for GCMs. Part III: The greening of the Colorado State University general circulation model , 1996 .

[11]  Phillip A. Arkin,et al.  Analyses of Global Monthly Precipitation Using Gauge Observations, Satellite Estimates, and Numerical Model Predictions , 1996 .

[12]  N. Zeng,et al.  A Land–Atmosphere Interaction Theory for the Tropical Deforestation Problem , 1999 .

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

[14]  Richard B. Rood,et al.  An assimilated dataset for Earth science applications , 1993 .

[15]  Germán Poveda,et al.  Feedbacks between Hydrological Processes in Tropical South America and Large-Scale Ocean–Atmospheric Phenomena , 1997 .

[16]  E. Rasmusson,et al.  Atmospheric Water Vapor Transport and the Water Balance of North America , 1968 .

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

[18]  J. Marengo,et al.  Observational and modelling studies of Amazonia interannual climate variability , 1993 .

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

[20]  C. Deser,et al.  Amazon River Discharge and Climate Variability: 1903 to 1985 , 1989, Science.

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

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