A comparative study of the land–atmosphere energy and water exchanges over the Tibetan Plateau and the Yangtze River Region

Abstract

A comprehensive understanding of energy and water cycle characteristics in different regions is crucial for studying local land–atmosphere interactions and predicting regional weather and climate change. To explore similarities and differences in land–atmosphere energy and water exchanges between two regions—the Tibetan Plateau (TP), characterized by higher elevation and a drier climate, and the Yangtze River Region (YRR), with lower elevation and a wetter climate—this study analyzed and compared the radiation components and the turbulent heat fluxes at eight sites covering various land-cover types, including alpine desert and alpine grassland on the TP, as well as urban and grassland on the YRR. The following results were obtained: (1) Over the TP, the annual mean incoming and outgoing shortwave radiation are 251.3 and 59.6 W m⁻², which are 1.70 and 2.87 times the values in the YRR, respectively. The incoming and outgoing longwave radiation are 231.5 and 338.0 W m⁻², which are 0.64 and 0.83 times those in the YRR, respectively. However, the difference in net radiation is relatively small. (2) In grassland over both the TP and YRR, the latent heat fluxes have higher values of 35.0 and 38.8 W m⁻², respectively, leading to a higher heating efficiency. Alpine desert has the highest sensible heat flux (SH) value of 42.1 W m⁻², due to sparse vegetation and lower soil moisture, followed closely by urban land cover with an average SH value of 38.2 W m⁻². These results highlight the different characteristics of land–atmosphere interaction across different land covers in different climatic contexts, laying the groundwork for future investigations of additional land–atmosphere coupling processes.

摘要

正确认识不同区域能量和水分循环特征是研究局地地气相互作用及准确预测区域天气, 气候变化的关键. 为了研究属于干旱/半干旱气候的青藏高原 (TP) 和湿润/半湿润气候的长江流域 (YRR) 之间地表能量和水分交换的异同, 本文对比分析了两个区域8个不同地表类型 (包括高山荒漠, 高山草地, (平原) 城市和 (平原) 草地等) 观测站点的地表辐射和能量通量数据. 结果显示: (1) TP由于高原大气层稀薄且空气洁净, 年平均入射短波辐射为251.3 W m⁻², 是YRR的1.7倍. 加之高原地表反照率高导致反射辐射 (59.6 W m⁻²⁾ 是YRR的2.87倍. 入射及出射的长波辐射为231.5和338.0 W m⁻², 分别为YRR的0.64和0.83. 而两个区域的净辐射差异不大; (2) 草地站更多的潜热释放使得地表总加热效率高于城市和高山荒漠, TP和YRR的草地站的年平均潜热分别为35.0 和 38.8 W m⁻², 而植被稀疏且土壤干燥的高山荒漠地区感热最大, 年平均感热为42.1 W m⁻²; 其次是城市下垫面, 其年平均感热为37.7 W m⁻². 研究结果揭示了不同气候背景下典型下垫面地气相互作用特征, 为地气相互作用过程深入分析奠定了基础.