Subseasonal variabilities of surface soil moisture in reanalysis datasets and CESM simulations

Using surface soil moisture (SM) from ERA-Interim reanalysis and Climate Forecast System Reanalysis (CFSR) data together with simulated results from CESM, the authors evaluated the subseasonal variability of SM and explored its basic features. Evident subseasonal variability of SM was detected in all seasons and with different datasets. However, the subseasonal variability of SM showed significant regional differences and varied with seasons. It was found that SM has large subseasonal variances in eastern China, North America, South Africa, and Australia in the summer hemisphere. The variances of the low-frequency SM variations given by ERA-Interim and CFSR are different. Overall, CFSR shows stronger variability than ERA-Interim. Through spectral analysis, it was noticed that low-frequency variations of surface SM mainly happen with periods of 10?30 days and 30?50 days. Subseasonal variations with a period of 10?30 days are dominant in eastern China and South Africa. However, subseasonal variations with periods of both 10?30 days and 30?50 days were detected in North America and Australia. Generally, CESM captures the main features of SM subseasonal variation. However, the model overestimates the subseasonal variability in all seasons in most regions, especially in the high latitudes of the Northern Hemisphere.