Fig. 3.

Probability distribution of soil moisture. The histograms show the soil moisture distribution estimated from the data of the Illinois soil moisture network (25, 26). Depth-average (top 50 cm) soil moisture values are taken from Peoria for the May–September seasons in the years 1980–2002. Similar behavior is found for soil moisture at different depths in at least two-thirds of the stations. The figure shows also the probability distribution of regional soil moisture calculated by the model with λ expressed as a linear function of s (solid line) and as a constant (λ = 0.35, dashed line). The λ = λ(s) function was the same as determined from data fitting (Fig. 1 A).