Characteristics and Controlling Factors of Regional-scale Variability in Surface Soil Moisture within Semi-arid Grassland in Mongolia(<Special Issue>Coordinated Enhanced Observing Period(CEOP))

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In this study, we monitored the surface soil moisture at 15 locations within an area of 100 km×100 km in the Mongolian steppe region. A principal component analysis was used to deter-mine the characteristics and dominant patterns of spatiotemporal variations in the measured surface soil moisture. The results reveal that the predominant pattern of temporal variation is related to large-scale rainfall and that this was spatially uniform over the entire study area. In terms of both temporal and spatial patterns, the spatial heterogeneity of rainfall activity was a minor factor, accounting for less than 33% of the total observed variance. The most dominant pattern in the spatial distribution of surface soil moisture showed a correlation with the spatial distribution of the mean or minimum water content, and the minimum water content was largely equivalent to the wilting point, which is a soil-hydraulic index. Thus, we conclude that the most dominant pattern of surface soil moisture distribution over the study region is regulated by soil-hydraulic properties. Rainfall events acted to disturb or reset this pat-tern, but the pattern was re-established during drying of the soil.
社団法人日本気象学会の論文
2007-02-28