The Impact of Agricultural Practices in China on Land-Atmosphere Interactions |
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| Authors: | XU Xingkui and Jason K LEVY |
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| Institution: | State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, Institute of Atmospheric Physics, Chinese Academy of Science, Beijing 100029,L. Douglas Wilder School of Government and Public Affairs, Virginia Commonwealth University Richmond, VA 23284 USA |
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| Abstract: | Human-induced land use changes and the resulting alterations in vegetation
features are major but poorly recognized drivers of regional climatic
patterns. In order to investigate the impacts of anthropogenically-induced
seasonal vegetation cover changes on regional climate in China, harmonic
analysis is applied to 1982--2000 National Oceanic and Atmospheric
Administration (NOAA) Advanced Very High Resolution Radiometer
(AVVHRR)-derived normalized difference vegetation index (NDVI) time series
(ten day interval data). For two climatic divisions of South China, it is
shown that the first harmonic term is in phase with air temperature, while
the second and third harmonics are in phase with agricultural cultivation.
The Penman-Monteith Equation and the Complementary Relationship Areal
Evapotranspiration (CRAE) model suggest that monthly mean evapotranspiration
is out of phase with temperature and precipitation in regions with
significant second or third harmonics. Finally, seasonal vegetation cover
changes associated with agricultural cultivation are identified: for cropped
areas, the temperature and precipitation time series have a single maximum
value, while the monthly evapotranspiration time series has a bimodal
distribution. It is hypothesized that multi-cropping causes the land surface
albedo to sharply increase during harvesting, thereby altering the energy
distribution ratio and contributing to observed seasonal vegetation cover
changes. |
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| Keywords: | NDVI land surface cover phenologies multi-crop latent heat discrete Fourier transform |
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