Liu et al., 2001
Liu, Suxia, Xingguo Mo, Haibin Li, Gongbing Peng, and Alan Robock, 2001:
Spatial variation of soil moisture in China: Geostatistical characterization.
J. Meteorol. Soc. Japan, 79, 555-574.
We analyze the large-scale spatial variation of soil moisture in eastern China
using geostatistical techniques with observations at 99 stations for the top
0.1 m and top 1 m from 1987 to 1989. Sample variograms are found to have a
clear sill and a nugget in many cases. A spherical variogram model, including a
nugget in some cases, fits the sample variograms closely. Using a quantitative
method to select the separation interval for variogram analysis, we find that
the average range is 200-400 km for the top 0.1 m and 400-700 km for the top 1
m. The averaged coefficient of variation of soil moisture in the top 0.1 m is
larger than for the top 1 m, showing that the range for the top 0.1 m is less
than for the top 1 m. The range in summer is less than in winter. By
calculating the ratio of the nugget effect to the spatial variance, we find
that the ratios for the top 0.1 m data are smaller than that for the top 1 m
data, showing that in most cases the spatial variation of the top 0.1 m is more
strongly autocorrelated than of the top 1 m, and that the measurement errors
are much larger in the top 1 m data than in the top 0.1 m. For more than half
of the measured dates, the ratio of the nugget effect to the variance is less
than 20 percent, indicating that the spatially correlated variation on those
dates can explain more than 80 percent of the total variance.
Prepared by Alan Robock (email@example.com ) - Last
updated on October 23, 2001