盘锦芦苇湿地参数化方案研究

【作者】 甄晓杰；

【导师】 周广胜；

【作者基本信息】 中国气象科学研究院 ， 大气物理学与大气环境， 2009， 硕士

【摘要】 湿地与森林、海洋并称为全球三大生态系统。长期以来,生态系统长期通量观测大都集中在草地,农田和森林生态系统,关于湿地的相关研究,特别是基于长期观测资料的研究甚少,制约着对湿地陆-气通量输送的准确估算。我国通量观测研究与网络建设起步较晚,涡度相关观测只有7年多的时间,且涡度相关系统仪器较为昂贵,难以普及。而风速、温度和湿度的梯度观测开始时间早,资料较易获取。因此,基于梯度观测资料获取陆-气通量成为人们关注的焦点。已有研究表明,目前基于梯度观测资料计算陆气通量的方法中,变分法(variational technique, VT)充分利用了边界层观测资料、Monin-Obukhov相似性理论和地表能量平衡方程,使算法更加稳定可靠,是目前除涡度相关技术外的最优计算方法。本研究利用盘锦芦苇湿地2005年和2006年的开路式涡度相关系统和微气象梯度系统观测资料定量描述了盘锦芦苇湿地下垫面的空气动力学特征及其统计不稳定性,分析了其主导影响因子。在此基础上,验证了B-D稳定度函数参数化方案的适用性。同时反演了盘锦芦苇湿地的变分法权重系数,探讨了其主导影响因子,提出了变分法权重系数的估算方法。主要结论如下:1)盘锦芦苇湿地非生长季的零平面位移(d)可按照Garratt建议的2/3植被高度(h)计算;生长季的d值和植被群落高度呈很好的线性相关关系,( d = 0.77h),略大于(2/3)h,可能与生长季湿地芦苇群落稠密有关;芦苇湿地粗糙度(z0)与叶面积指数(LAI)呈二次曲线关系,z0/h随LAI增大迅速减小并逐渐趋于稳定。2)盘锦芦苇湿地近地面层一般不存在极稳定或极不稳定的层结,经常维持弱稳定和弱不稳定层结。3)基于观测资料拟合的盘锦芦苇湿地近地面层不稳定层结(-0.4<z/L<-0.01)下的动量和感热稳定度函数与B-D参数化方案较为一致,B-D方案适用于盘锦芦苇湿地近地面层湍流通量计算。需要指出的是,在此稳定度范围之外B-D方案的适用性还需进一步验证。4)初步建立了估算变分法权重系数的统计学方法,指出变分法权重系数在不同月份并不相同,变分法权重系数不仅与仪器误差有关,还受下垫面植被生长的动态影响,包括植被高度和零平面位移等。5)与涡度相关方法相比较,变分法受能量平衡方程的限制,能量闭合度更高,水热通量之和更加集中在有效能附近,与已有的研究结果相吻合。更多还原

【Abstract】 Wetland, forest and ocean ecosystems are the three most important ecosystems in the world. At present, the long-term studies on ecosystem flux exchanges are concentrated in the forest and grassland ecosystems. There are few studies about wetland ecosystems. It restricts the understanding and the accurate estimation of the land-atmosphere flux exchanges in wetland ecosystems.The observations and researches on the land-atmosphere flux exchanges and the construction of the flux network in our country started relatively late. There are only 7 years about eddy correlation observations, and the eddy covariance system is too expensive to popularize. But two height layers’wind speed, temperature and humidity gradient observations started more early and the data were easier to access. Therefore, the estimation of land-atmosphere flux exchanges based on the micrometeorological gradient observation database has become the hot focus. Variational method is often taken as the better method calculating land-atmosphere flux exchanges based on the micrometeorological gradient observation database, which made full use of the boundary layer observational data, Monin-Obukhov similarity theory and the surface energy balance equation.Based on the data from the open eddy correlation system and micrometeorological gradient system in Panjin reed wetland in the years of both 2005 and 2006, a quantitative description of the surface aerodynamic characteristics and their statistical instabilities and their main controlling factors have been analyzed. On this basis, the applicability of B-D stability function was analyzed at this site. Based on the surface aerodynamic parameters and the data from those two systems, the weighting coefficients of variational method and their controls were studied. A method to estimate the weighting coefficients of variational method was proposed. The main conclusions were listed as follows:1) In non-growing season, the zero plane displacement (d) of reed ecosystem can be calculated according to 2/3h at this site as the formula suggested by Garrett. In growing season, d and the height of the plant (h) has a very good linear correlation: d=0.77h. The zero plane displacement is bigger than 2/3h, it’s probably caused by a dense reed community in the growing season. z0/h has a quadratic curve correlation with LAI. z0/h firstly decreases rapidly with increasing LAI, then changes very little.2) The atmospheric stability in the atmospheric surface layer of Panjin reed wetland often maintains weak stability and unstability.3) Businger-Dyer stability function parameter schemes could be used in Panjin reed wetland under the atmospheric stability (-0.4< z/L<-0.1). The parameterization scheme in the atmospheric surface layer of Panjin reed wetland needs further study, when the stability function is beyond the range of the atmospheric stability (-0.4< z/L<-0.1).4) This study developed the preliminary statistical method for estimating weighting coefficients of the variational method. The weighting coefficients are various among different months, and they are not only related with the observation error of the instrument, but also related with the height of plant, zero-plane displacement et al.5) Compared with the eddy correlation method, the variational method subjects to the restrictions on energy balance equation, the sum of sensible heat flux and latent heat flux is more concentrated in the vicinity of the effective energy.更多还原