青藏高原土壤水分变化对近地面气温的影响

青藏高原为全球气候变化最为敏感的区域之一,探讨该地区土壤水分变化对近地面气温的影响将为青藏高原水汽循环研究及该地区对周边气候与环境的影响研究提供重要理论支撑。利用NCEP-CFSR数据集,基于土壤水分对近地面气温的影响机理,揭示了青藏高原不同季节、不同植被分区下土壤水分时空分异规律、土壤水分与蒸发率的响应与耦合状态及土壤水分通过蒸散发过程对近地面气温的影响。结果表明：① 不同季节下青藏高原土壤水分空间分布基本一致,除西北地区和喜马拉雅山脉外,整体呈现由东南向西北递减趋势,青藏高原地区存在干旱区变湿,湿润区变干的空间特征;② 青藏高原大部分区域土壤水分处于干湿过渡状态,其中青藏高原南部和东南部地区全年处于干湿过渡状态,而柴达木盆地几乎全年处于干旱状态;③ 近地面气温对土壤水分的响应在冬季最弱,在夏季最强且空间差异较小,其中在冬、春、夏季为负反馈,另外不同植被覆盖区近地面气温对土壤水分的敏感性差异很大。此项研究对于进一步探讨青藏高原地区陆气耦合状态及变化环境下的区域水汽循环及其效应具有重要理论意义。

Effect of soil moisture variation on near-surface air temperature over the Tibetan Plateau

The Tibetan Plateau is one of the most sensitive regions to global climate change. It is of important theoretical significance to explore the effect of soil moisture changes on near-surfaceair temperature for the study of the water cycle of the Tibetan Plateau and its impact on the surrounding climate and environment. Based on the NCEP-CFSR dataset, this paper reveals the spatial-temporal pattern of soil moisture content in different seasons and different vegetation zones on the Tibetan Plateau, the response and coupling of soil moisture and evaporation rate, and the impact of soil moisture on near-surface air temperature through evapotranspiration. The results show that: (1) The spatial pattern of soil water on the Tibetan Plateau is basically similar in different seasons, showing a decreasing trend from southeast to northwest and the spatial characteristics of drying in humid regions and wetting in arid regions; (2) The soil moisture in most parts of the Tibetan Plateau is in a transitional state, in which the southern and southeastern parts of the plateau are in a state of transition throughout the year, while the soil moisture in the Qaidam Basin is almost in a dry state all the year round; (3) The sensitivity of the near-surface air temperature to soil moisture is the weakest in winter, but the strongest in summer with weak spatial difference, which is negative feedback in winter, spring and summer. Moreover, the sensitivity of air temperature to soil moisture varies greatly in different vegetation coverage areas. This study has important theoretical significance for further exploring the regional water cycle and its effects under the coupled land-atmosphere state and the changing environment of the Tibetan Plateau.