Editorial Type:
Article
Article Type:
Research Article

Application of a GCM to Study the Surface Hydrological Budget of Amazonia

Loren D. White Center for Ocean–Atmospheric Prediction Studies, The Florida State University, Tallahassee, Florida

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Mukul Tewari Department of Meteorology, The Florida State University, Tallahassee, Florida

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T. N. Krishnamurti Department of Meteorology, The Florida State University, Tallahassee, Florida

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Print Publication:
01 Oct 1998
DOI:
https://doi.org/10.1175/1520-0450(1998)037<1321:AOAGTS>2.0.CO;2
Page(s):
1321–1331
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Abstract

Using The Florida State University Global Spectral Model, hydrological budgets are calculated over the Amazon River basin for the boreal summer of 1979 with and without a complex biosphere model (BATS) coupled to the atmospheric model. Substantially increased precipitation and latent heat fluxes over the Amazon are noted for the BATS case, along with better maintenance of low-level flow patterns. Partitioning of the rainfall and latent heat flux into detailed component terms from BATS reveals evidence of “moisture recycling,” particularly in relation to the intercepted rainfall. Monthly variations in the component terms for precipitation, latent heat flux, and upper soil moisture are described. A total runoff efficiency of 75% is simulated by the model, while the surface runoff efficiency is about 30%. Model performance in the locality of two intensive field study areas (Pará and Rondônia) of the Large-Scale Biosphere–Atmosphere Experiment in Amazonia has been examined via time series from the two models and observed data. The 850-hPa temperatures and wind speeds are both overestimated by the models. However, use of BATS has reduced the temperature bias by about 30%. Most significantly, the phase of the wind speed variations over Rondônia is maintained in agreement with the observations throughout the seasonal forecast.

Corresponding author address: Dr. Loren D. White, COAPS, Florida State University, Tallahassee, FL 32306-3041.

Abstract

Using The Florida State University Global Spectral Model, hydrological budgets are calculated over the Amazon River basin for the boreal summer of 1979 with and without a complex biosphere model (BATS) coupled to the atmospheric model. Substantially increased precipitation and latent heat fluxes over the Amazon are noted for the BATS case, along with better maintenance of low-level flow patterns. Partitioning of the rainfall and latent heat flux into detailed component terms from BATS reveals evidence of “moisture recycling,” particularly in relation to the intercepted rainfall. Monthly variations in the component terms for precipitation, latent heat flux, and upper soil moisture are described. A total runoff efficiency of 75% is simulated by the model, while the surface runoff efficiency is about 30%. Model performance in the locality of two intensive field study areas (Pará and Rondônia) of the Large-Scale Biosphere–Atmosphere Experiment in Amazonia has been examined via time series from the two models and observed data. The 850-hPa temperatures and wind speeds are both overestimated by the models. However, use of BATS has reduced the temperature bias by about 30%. Most significantly, the phase of the wind speed variations over Rondônia is maintained in agreement with the observations throughout the seasonal forecast.

Corresponding author address: Dr. Loren D. White, COAPS, Florida State University, Tallahassee, FL 32306-3041.

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Journal of Applied Meteorology and Climatology

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