SCIENTIFIC BACKGROUND AND OBJECTIVES. As the highest plateau in the world, the Tibetan Plateau (TP) directly impacts its surrounding climate and environment through atmospheric and hydrological processes. Meanwhile, the TP climate changed significantly (such as rapid warming, moistening, solar dimming, and wind stilling) over the past 30 years , which further altered its environment (e.g., glacier retreat, lake expansion, and permafrost degradation, etc.) and brought environmental risks and disasters to the plateau's surrounding regions. The "third pole" was proposed as a geographic element to cover the TP and its adjacent mountains (Qiu 2008), and the "Third Pole Environment" (TPE) was then launched as an international program in 2009, with intension to pool international efforts to reveal and quantify the "water-ice-air-ecosystem-human" interactions in this region (Yao et al. 2012). Among the multisphere interactions on the TP, soil moisture (SM) plays a fundamental role in controlling land surface energy partition, adjusting surface runoff and soil drainage, regulating canopy transpiration and carbon AFFILIATIONS: yang, Qin, y. Chen, anD Tang-key laboratory of tibetan environment changes and land surface Processes, institute of tibetan Plateau research, chinese Academy of sciences, Beijing, china; Zhao, han, LaZhu, Ding, Wu, anD Lin-key laboratory of tibetan environment changes and land surface Processes, institute of tibetan Plateau research, chinese Academy of sciences, and university of chinese Academy of sciences, Beijing, china; Z. Chencollege of global change and earth system science, Beijing normal university, Beijing, china; Lv-state key laboratory of resources and environmental information system, institute of geographic sciences and natural resources research, chinese Academy of sciences, Beijing, china CORRESPONDING AUTHOR: kun Yang, institute of tibetan Plateau research, chinese Academy of sciences, Bldg. 3, courtyard 16, lincui rd., chaoyang district,

Two soil moisture and temperature monitoring networks were established in the Tibetan Plateau (TP) during recent years. One is located in a semihumid area (Naqu) of central TP and consists of 56 soil moisture and temperature measurement (SMTM) stations, the other is located in a semiarid area (Pali) of southern TP and consists of 21 SMTM stations. In this study, the station data are used to evaluate soil moisture retrievals from three microwave satellites, i.e., the Soil Moisture Active Passive (SMAP) of NASA, the Soil Moisture and Ocean Salinity (SMOS) of European Space Agency, and the Advanced Microwave Scanning Radiometer 2 (AMSR2) of Japan Aerospace Exploration Agency. It is found that the SMAP retrievals tend to underestimate soil moisture in the two TP networks, mainly due to the negative biases in the effective soil temperature that is derived from a climate model. However, the SMAP product well captures the amplitude and temporal variation of the soil moisture. The SMOS product performs well in Naqu network with acceptable error metrics but fails to capture the temporal variation of soil moisture in Pali network. The AMSR2 products evidently exaggerate the temporal variation of soil moisture in Naqu network but dampen it in Pali network, suggesting its retrieval algorithm needs further improvements for the TP.

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The ability of FLake, WRF‐Lake, and CoLM‐Lake models in simulating the thermal features of Lake Nam Co in Central Tibetan Plateau has been evaluated in this study. All the three models with default settings exhibited distinct errors in the simulated vertical temperature profile. Then model calibration was conducted by adjusting three (four) key parameters within FLake and CoLM‐Lake (WRF‐Lake) in a series of sensitive experiments. Results showed that each model's performance is sensitive to the key parameters and becomes much better when adjusting all the key parameters relative to tuning single parameter. Overall, setting the temperature of maximum water density to 1.1 °C instead of 4 °C in the three models consistently leads to improved vertical thermal structure simulation during cold seasons; reducing the light extinction coefficient in FLake results in much deeper mixed layer and warmer thermocline during warm seasons in better agreement with the observation. The vertical thermal structure can be clearly improved by decreasing the light extinction coefficient and increasing the turbulent mixing in WRF‐Lake and CoLM‐Lake during warm seasons. Meanwhile, the modeled water temperature profile in warm seasons can be significantly improved by further replacing the constant surface roughness lengths by a parameterized scheme in WRF‐Lake. Further intercomparison indicates that among the three calibrated models, FLake (WRF‐Lake) performs the best to simulate the temporal evolution and intensity of temperature in the layers shallower (deeper) than 10 m, while WRF‐Lake is the best at simulating the amplitude and pattern of the temperature variability at all depths.

The recent growth and deepening of inland lakes in the Tibetan Plateau (TP) may be a salient indicator of the consequences of climate change. The seasonal dynamics of these lakes is poorly understood despite this being potentially crucial for disentangling contributions from glacier melt and precipitation, which are all sensitive to climate, to lake water budget. Using in situ observations, satellite altimetry and gravimetry data, we identified two patterns of lake level seasonality. In the central, northern, and northeastern TP, lake levels are characterized by considerable increases during warm seasons and decreases during cold seasons, which is consistent with regional mass changes related to monsoon precipitation and evaporation. In the northwestern TP, however, lake levels exhibit dramatic increases during both warm and cold seasons, which deviate from regional mass changes. This appears to be more connected with high spring snowfall and large summer glacier melt. The variable lake level response to different drivers indicates heterogeneous sensitivity to climate change between the northwestern TP and other regions.

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The weather research and forecasting model including a one-dimensional thermal diffusion lake model is adopted to investigate the summer climatic effect of the lake clusters over Tibetan Plateau (TP) during 2008-2014 based on two experiments with and without the lakes. Overall, the model can reasonably reproduce the daily variations of lake surface temperature and the spatial patterns of 2 m air temperature (T 2m) and precipitation over TP during summer. Sensitivity results show that the effects of TP lakes on the over-lake T 2m and precipitation exhibit distinctive seasonal and diurnal features and strong space dependence. Generally, the TP lakes tend to cool the local T 2m and enhance the precipitation over the lake and surrounding areas. With the summer advances, the cooling effect of TP lakes weakens while the lake-induced enhancement of precipitation becomes more evident. During daytime, the TP lakes decrease the T 2m and suppress the short-duration (≤ 6 h) rainfall in afternoon. However, the TP lakes increase the T 2m and strengthen the convective rainfall over the lake and surrounding areas by simultaneously enhancing both short and long-duration (> 6 h) precipitation during nighttime. The lakes over the southeastern central TP (CTP) lead to slight warming and pronounced precipitation increases, while the other lakes in CTP mainly cause significant cooling and suppressed precipitation. Such opposite effects are mainly because the lakes over the western and northeastern CTP hardly produce nighttime warming and the associated circulation changes favorable for the convective precipitation as found over the southeastern CTP, suggesting that the climate effects of TP lakes may be modulated by the lake intrinsic features, local terrain distributions, and background atmospheric circulations.