Mesoscale Eddies Affect Near-Surface Turbulent Exchange: Evidence from Lidar and Tower Measurements
Mesoscale Eddies Affect Near-Surface Turbulent Exchange: Evidence from Lidar and Tower Measurements
复制标题
DOI：
10.1175/jamc-d-14-0140.1
复制
发表时间：
2015-01-01
影响因子：
3
通讯作者：
Mauder, Matthias
中科院分区：
文献类型：
--
作者：
Eder, Fabian;Schmidt, Marius;Mauder, Matthias
涡度相关技术往往低估湍流热通量，这将导致地表能量平衡的不闭合。这项研究表明，实验证据表明，中尺度湍流有组织的结构，这是固有的不捕获的标准涡协方差技术，可以影响近地面湍流交换。在德国农田为主的地区，通过使用三台多普勒测风激光雷达的组合装置，在地面几米以上的表层探测到低频湍流结构。此外，从两个微气象站在研究区域的数据进行了分析，就能量平衡关闭。根据以前的几项研究，数据证实了强烈的摩擦速度依赖的能量平衡残留。在这两个站，能量平衡残差被认为是正相关的垂直湿度梯度在低层大气边界层，但只有一个站是它与温度梯度。这一结果表明，中尺度输送对潜热通量的贡献可能大于对感热通量的贡献，但这一结论在很大程度上取决于测量地点。此外，由于塔架安装和测量装置造成的气流畸变对某些风向的能量平衡闭合有很大影响。
The eddy-covariance technique tends to underestimate turbulent heat fluxes, which results in nonclosure of the surface energy balance. This study shows experimental evidence that mesoscale turbulent organized structures, which are inherently not captured by the standard eddy-covariance technique, can affect near-surface turbulent exchange. By using a combined setup of three Doppler wind lidars above a cropland-dominated area in Germany, low-frequency turbulent structures were detected in the surface layer down to a few meters above ground. In addition, data from two micrometeorological stations in the study area were analyzed with respect to energy balance closure. In accordance with several previous studies, the data confirm a strong friction velocity dependence of the energy balance residual. At both stations, the energy balance residual was found to be positively correlated with the vertical moisture gradient in the lower atmospheric boundary layer, but at only one station was it correlated with the temperature gradient. This result indicates that mesoscale transport probably contributes more to the latent heat flux than to the sensible heat flux, but this conclusion depends largely on the measurement site. Moreover, flow distortion due to tower mountings and measurement devices affects the energy balance closure considerably for certain wind directions.