黄河源高寒湿地-大气间暖季水热交换特征及关键影响参数研究

湿地是由陆地和水体形成的自然综合体，具有重要的生态、水文和生物地球化学功能，黄河源高寒湿地作为黄河重要的水源涵养区，对其下垫面水热交换特征及关键影响参数的研究具有非常重要的意义。本文利用中国科学院西北生态环境资源研究院麻多黄河源气候与环境变化观测站2014年6~8月观测资料，分析了黄河源区高寒湿地-大气间暖季水热交换特征，并利用公用陆面模式（Community Land Model，简称CLM）模拟了热通量变化，提出针对高寒湿地的粗糙度优化方案。主要结果如下:（1）暖季向上、向下短波与净辐射的平均日变化规律一致，向上、向下长波平均日变化平缓，地表温度升高相对于向下短波具有滞后性，潜热通量始终为正值并大于感热通量；（2）温度变化显著层结为20 cm以上土壤浅层，存在明显的日循环规律，土壤中热量09:00（北京时，下同）下传至5 cm深度，温度升高，11:00至10 cm深度，13:00至20 cm深度，18:00后开始上传，温度降低，40 cm及以下深度受此影响较小，热量在土壤中整体由浅层向深层输送；（3）土壤湿度平均日变化小，5 cm深度为土壤湿度最小层，10 cm深度为最大层；（4）麻多高寒湿地动力学粗糙度Z_0m在暖季变化稳定，可作为常数，Z_0m=0.0143 m；（5）提出更加适合高寒湿地下垫面暖季附加阻尼kB-1参数化方案，使得热通量模拟效果较CLM原始方案有所提高。以上结果对于研究湿地下垫面陆面过程具有重要意义。

Characteristics of Water and Heat Exchanges and Their Crucial Influencing Factors on the Alpine Wetland during the Warm Season in the Source Region of the Yellow River

Wetland is a natural complex of land and water, which has important functions in ecology, hydrology and biogeochemistry. The alpine wetland in the source region of the Yellow River (SRYR) is a key water conservation area of the Yellow River, and it is important to understand the characteristics of water and heat exchanges and their crucial influencing factors in this region. In this paper, the characteristics of water and heat exchanges are analyzed using the field observation data provided by Maduo Climate and Environment Monitoring Labotory of Nothwest Institute of Eco-Environment and Resources, CAS (Chinese Academy of Sciences) for June-August 2014 over the alpine wetland in the SRYR. The Community Land Model (CLM) is applied to simulate heat flux. A roughness length scheme, which aims at the alpine wetland, is designed based on the simulation results. The main results are as follows:(1) The upward and downward short-wave radiation and net radiation fluxes in the warm season have similar diurnal variation patterns, and the diurnal fluctuations of the upward and downward long-wave radiation fluxes are small. The increase in surface temperature lags the increases in downward shortwave radiation flux, and the latent heat flux is always positive and greater than the sensible heat flux. (2) The soil layer in which temperature has significant changes is the top shallow layer in 0-20 cm depth, where there exists an obvious diurnal cycle of temperature variation. The soil temperature starts increasing when heat is transferred down to 5 cm depth at 0900 BJT (Beijing time), and the heat reaches 10 cm depth at 1100 BJT and 20 cm depth at 1300 BJT. Soil temperature starts decreasing because of the upward transfer of heat after 1800 BJT. The soil layer below 40 cm is hardly influenced by the radiation flux, and the general characteristics of heat transfer is from the shallow top layer to deep layers. (3) The diurnal variation of soil moisture is small, and the soil at 5 cm and 10 cm depths have the minimum and maximum moisture content, respectively. (4) The roughness length for momentum (Z_0m) over the alpine wetland in Maduo during the warm season is stable, which can be set to be a constant Z_0m=0.0143 m. (5) The newly added damping kB^-1 schemes are designed for local alpine wetland, which have a better performance in simulating the surface heat flux than the original scheme of CLM. All these results have significant contributions to the research of land surface process over the wetland.