Dy. Chen et W. Brutsaert, DIAGNOSTICS OF LAND-SURFACE SPATIAL VARIABILITY AND WATER-VAPOR FLUX, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 100(D12), 1995, pp. 25595-25606
To assess the spatial variability of the water vapor (i.e., latent hea
t) flux LE, it is convenient to scale it with its equilibrium analog L
E(e). From an analysis of the data from the First International Satell
ite Land Surface Climatology Project (ISLSCP) Field Experiment, or FIF
E, the spatial distribution of daily values of this dimensionless evap
oration, alpha = LE/LE(e), was found to be strongly related to the dis
tributions of soil moisture and of the state of the vegetation. Howeve
r, the relative strengths of these relationships depended on the soil
moisture content and on its distribution. When the mean soil moisture
content SM was high, in excess of about 27%, the distribution of evapo
ration was quite uniform regardless of the vegetation uniformity. In t
he intermediate range, with 20 < SM < 27%, both soil moisture and vege
tation contributed to the spatial distribution of alpha. This distribu
tion was controlled by the vegetation, when the soil moisture was unif
orm; under nonuniform soil moisture conditions, however, soil moisture
exerted the major control. For SM < 20%, soil moisture normally was n
onuniform, and it was found to hold the primary control of the spatial
variation of alpha. The daily distribution of soil moisture content w
as largely independent from that of the state of the vegetation, due t
o the different timescales involved.