HR: 17:00h
AN: H24B-05    [Abstracts]
TI: On the Transient Correlation Structure of Water Vapor and Carbon Dioxide Time Series Over Low-Profile Vegetation
AU: * Scanlon, T M
EM: tms2v@virginia.edu
AF: University of Virginia, Department of Environmental Sciences Clark Hall, Charlottesville, VA 22904, United States
AU: Sahu, P
EM: ps7uc@virginia.edu
AF: University of Virginia, Department of Environmental Sciences Clark Hall, Charlottesville, VA 22904, United States
AB: Much work has previously centered on temperature and water vapor similarity as a result of its application to the flux-variance method. Less attention, however, has been paid to similarity between carbon dioxide and water vapor. In this study, we analyze water vapor and carbon dioxide time series to infer causes of departure from correlation coefficients of +/-1. Photosynthesis and transpiration, both stomatal processes, have identical sources and sinks. Therefore, under hypothetical conditions in which carbon and water fluxes are comprised of only these two components, the effects of entrainment (which operates at a large scale) and differences in molecular diffusivities between water vapor and carbon dioxide (which operates at a small scale) can cause degradation in the correlation between the two time series. Under more realistic conditions in which the non- stomatal processes of respiration and bare evaporation are active, additional degradation is imparted upon the correlation. The correlation structure between water vapor and carbon dioxide time series is analyzed using high- frequency data collected over an early-growth corn field on the Eastern Shore of Virginia. We contrast the correlations observed following a long dry-down period with those observed shortly after a significant rainfall, when both bare soil evaporation and respiration fluxes became enhanced. Wavelet analysis is applied to the time series to distinguish between the effects of small-scale vs. large-scale process on the degradation of the correlation.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 1813 Eco-hydrology
DE: 1818 Evapotranspiration
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
SC: Hydrology [H]
MN: 2007 Fall Meeting