Abstract: Based on soil moisture data of three observations in Shanghai,the characteristics of temporal variability of soil moisture were analyzed using trend analysis method with VBA tools for programming and Surfer 8 for map expression.The results showed that monthly variability of 10cm depth of soil moisture fluctuated violently with the lowest soil water content,while 50cm depth of soil moisture fluctuated steadily with the highest soil water content.The monthly fluctuation of different soil depths was basically identical.The highest soil water content of sunny and cloudy day appeared in spring and the lowest in autumn,the highest of overcast day appeared in summer and the lowest in autumn,the highest of rainy day appeared in summer and the lowest in winter.The minimum differences of soil water content among seasons appeared in sunny day while the maximum one in overcast day.The highest soil moisture of each season all appeared in rainy day and the distributions of soil water content under different weather types were basically identical in spring and winter.

Key words: Shanghai, Soil moisture, Monthly and seasonal variation