•RESEARCH PAPER• https://doi.org/10.1007/s11430-019-9554-8 ........................................................................................................... Method development for estimating soil organic carbon content in an alpine region using soil moisture data Qi LUO 1,2 , Kun YANG 1,3,4* , Yingying CHEN 1,4 & Xu ZHOU 1 1 Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; 2 University of Chinese Academy of Sciences, Beijing 100049, China; 3 Department of Earth System Science, Tsinghua University, Beijing 100084, China; 4 CAS Center for Excellence in Tibetan Plateau Earth System, Beijing 100101 China, China Received January 24, 2019; revised November 19, 2019; accepted November 22, 2019 Abstract The high soil organic carbon (SOC) content in alpine meadow can significantly change soil hydrothermal properties and further affect the soil temperature and moisture as well as the surface water and energy budget. Therefore, this study first introduces a parameterization scheme to describe the effect of SOC content on soil hydraulic and thermal parameters in a land surface model (LSM), and then the SOC content is estimated by minimizing the difference between observed and simulated surface-layer soil moisture. The accuracy of the estimated SOC content was evaluated using in situ observation data at a soil moisture and temperature-measuring network in Naqu, central Tibetan Plateau. Sensitivity experiments show that the optimum time window for stabilizing the estimation results cannot be shorter than three years. In the experimental area, the estimated SOC content can generally reflect the spatial distribution of the measurements, with a root mean square error of 0.099 m 3 m −3 , a mean bias of 0.043 m 3 m −3 , and a correlation coefficient of 0.695. The estimated SOC content is not sensitive to the temporal frequency of the soil moisture data input. Even if the temporal frequency is as low as that of current soil moisture products derived from passive microwave satellites, the estimation result is still stable. Therefore, by combining a high-quality satellite soil moisture product and a parameter optimization method, it is possible to obtain grid-scale effective parameter values, such as SOC content, for an LSM and improve the simulation ability of the LSM. Keywords Land surface model, Soil organic carbon content, Soil porosity, Soil parameter estimation Citation: Luo Q, Yang K, Chen Y, Zhou X. 2019. Method development for estimating soil organiccarbon content in an alpine region using soil moisture data. Science China Earth Sciences, 62, https://doi.org/10.1007/s11430-019-9554-8 1. Introduction In earth system models and climate system models, a land surface process model (LSM) is an important component that determines the water, energy, and carbon flux between land and atmosphere. Soil hydrothermal parameters are important inputs for land surface simulations (Henderson-Sellers et al., 1993; Shi et al., 2005), and their uncertainties may lead to large errors in simulation results (Gutmann and Small, 2005; Liu et al., 2005; Guo and Wang, 2013). With the develop- ment of LSMs, it is noted that soil organic carbon (SOC) has distinct hydrothermal properties from mineralized soils and has a great impact on soil water and heat transfer and surface fluxes (Yang et al., 2005; Lawrence and Slater, 2008; Chen et al., 2012). In addition to the large amount of SOC stored in the soil of the Pan-Arctic region, the Tibetan Plateau accu- mulates abundant SOC in its central and eastern regions dominated by alpine meadows due to slow decomposition of organic matter in the cold climate. This phenomenon has attracted much attention in recent years (Gao et al., 2015; Luo et al., 2017). Some LSMs have considered the effect of SOC content on simulation results, but there is a lack of © Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature 2019 earth.scichina.com link.springer.com SCIENCE CHINA Earth Sciences * Corresponding author (email: yangk@itpcas.ac.cn)