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Estimation of area‐averaged moisture flux
Author(s) -
Mahrt L.,
Kotwica K.,
Sun Jielun,
Macpherson J. I.,
Desjardins R. L.
Publication year - 1998
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49712455213
Subject(s) - environmental science , evapotranspiration , zenith , albedo (alchemy) , atmospheric sciences , vegetation (pathology) , leaf area index , flux (metallurgy) , solar zenith angle , atmosphere (unit) , remote sensing , meteorology , geology , geography , medicine , art , ecology , materials science , pathology , performance art , biology , art history , metallurgy
Abstract Toward the goal of predicting area‐averaged evapotranspiration, the evaporative fraction is modelled in terms of surface radiation temperature, air temperature, solar zenith angle, Normalized Difference of the Vegetation Index and albedo. Previous relationships break down when applied simultaneously to a variety of surfaces. The zenith angle is required to account for the influence of shaded ground on the remotely sensed surface radiation temperatures. The model of evaporative fraction is developed from Canadian Twin Otter aircraft data from the BOReal Ecosystem‐Atmosphere Study and the California Ozone Deposition Experiment. The model consists of separate submodels for active agriculture, forested surfaces, bare soil/senescent vegetation and water surfaces. These broad land‐use groups are effectively determined from remotely sensed red and near‐infrared reflectances. The area‐averaged moisture flux predicted by the model compares favourably with that computed from independent data over forested surfaces. However, the model performs poorly over bare soil/senescent surfaces, and data for a wider variety of surface conditions are required before the generality of the model can be evaluated.