ADVANCES IN ATMOSPHERIC SCIENCES, VOL. 27, NO. 2, 2010, 303–314 Comparisons of Soil Moisture Datasets over the Tibetan Plateau and Application to the Simulation of Asia Summer Monsoon Onset BAO Qing ∗ 1 ( ), LIU Yimin 1 ( ), SHI Jiancheng 2 ( ), and WU Guoxiong 1 ( ) 1 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 2 Institute for Computational Earth System Science, University of California, Santa Barbara, USA (Received 30 August 2008, revised 8 June 2009) ABSTRACT The influence of soil moisture on Asian monsoon simulation/prediction was less studied, partly due to a lack of available and reliable soil moisture datasets. In this study, we firstly compare several soil moisture datasets over the Tibetan Plateau, and find that the remote sensing products from the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) can capture realistic temporal variations of soil moisture better than the two reanalyses (NCEP and ECMWF) during the pre-monsoon seasons. Using the AMSR-E soil moisture product, we investigate the impacts of soil moisture over the Tibetan Plateau on Asian summer monsoon onset based on a Spectral Atmospheric Model developed at IAP/LASG (SAMIL). Comparison between results with and without the assimilation of remotely sensed soil moisture data demonstrates that with soil moisture assimilated into SAMIL, the land-sea thermal contrast during pre-monsoon seasons is more realistic. Accordingly, the simulation of summer monsoon onset dates over both the Bay of Bengal and South China Sea regions are more accurate with AMSR-E soil moisture assimilated. This study reveals that the application of the soil moisture remote sensing products in a numerical model could potentially improve prediction of the Asian summer monsoon onset. Key words: soil moisture, remote sensing, AMSR-E and ASM onset Citation: Bao, Q., Y. M. Liu, J. C. Shi, and G. X. Wu, 2010: Comparisons of soil moisture datasets over the Tibetan Plateau and application to the simulation of Asia summer monsoon onset. Adv. Atmos. Sci., 27(2), 303–314, doi: 10.1007/s00376-009-8132-5. 1. Introduction Soil moisture plays an important role in land- atmosphere interactions. Numerical results derived from both a simple general circulation model (Yeh et al., 1984) and Global Land Atmosphere Coupling Experiments (Koster et al., 2004) suggest that strong land-atmosphere coupling can be modified by soil moisture, and its anomalies can persist for months. Currently, the shortage of reliable soil moisture datasets has become a major obstacle to studying the impact of soil moisture on weather/climate variabil- ity. The Project for Inter-comparison of Land-surface Parameterization Schemes and Global Soil Wetness Project has suggested that no model is able to give a perfect simulation for the temporal and spatial vari- ations of soil moisture (Ma et al., 2001). Since the brightness temperature can vary noticeably with the presence of soil moisture, remote sensing has been an state-of-the-art technique to obtain a large-scale temporal and spatial characterization of soil mois- ture fields. But current satellite remote sensing data products have uncertainties due to imperfect instru- ment calibration and inversion algorithms, geophysi- cal noise, representation error, communication break- downs, and other sources. Therefore, it is essential to ∗ Corresponding author: BAO Qing, baoqing@mail.iap.ac.cn