Generation of free convection in a valley due to changes of the local circulation system
Generation of free convection in a valley due to changes of the local circulation system
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由于局部循环系统的变化而在山谷中产生自由对流
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发表时间：
2008
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通讯作者：
R. Eigenmann
中科院分区：
文献类型：
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作者：
R. Eigenmann
2007年6月1日至8月31日期间，在黑森林低山脉Kinzig山谷进行COPS（对流和地形诱发降水研究）野外活动期间安装了两个能量平衡站的表面能量交换测量，用于调查由当地环流系统变化引发的自由对流事件（FCE）的产生。这些 FCE 被认为对 ABL 热力学和结构具有重要影响。最近，梅耶尔等人。 (2008) 观察到 FCE，它起源于山谷，导致早晨山顶 (Hohenpeissenberg) 的臭氧发生强烈而突然的减少。在他们的研究中，发现 FCE 是由同时发生的最小风速触发的，有利于自由对流的条件。在大约一半的日子里，这些风速最小值可归因于高山前陆的高山泵送（Winkler et al., 2006; Lugauer and Winkler, 2005），与风向变化导致水平风速下降有关。因此，由复杂地形引发的其他中尺度或局部环流系统预计会触发 FCE。在 Kinzig 山谷中，观察到了清晰的昼夜热诱发山谷风系统（例如 Meißner 等人，2007 年），从而提供了检查这种剧烈的垂直输送机制是否被常见通量测量技术充分捕获的机会（Mayer 等人，2008 年），例如涡度协方差（EC）方法。总而言之，这项研究证明了适应能量交换测量的深刻的质量保证和控制工作及其对自由对流事件（FCE）的选择和描述的适用性。
Surface energy exchange measurements of two energy balance stations installed from June 1 to August 31, 2007 during the COPS (Convective and Orographically-induced Precipitation Study) field campaign in the Kinzig valley within the low mountain range of the Black Forest are used to investigate the generation of free convection events (FCEs) initiated by a change of the local circulation system. These FCEs are assumed to have an essential impact on ABL thermodynamics and structure. Recently, Mayer et al. (2008) observed FCEs, which originated from a valley and led to a strong and sudden ozone decrease at a mountain summit (Hohenpeissenberg) in the morning hours. In their study, the FCEs were found to be triggered by a simultaneously occurring wind speed minimum facilitating the conditions for free convection. On about half of the days these wind speed minima could be attributed to the onset of Alpine Pumping in the alpine foreland (Winkler et al., 2006; Lugauer and Winkler, 2005) associated with a change of wind direction causing a drop of the horizontal wind speed. Hence, other meso-scale or local circulation systems initiated by complex terrain are expected to trigger FCEs. In the Kinzig valley, a clear diurnal thermally-induced valley wind system was observed (e.g. Meißner et al., 2007), thus providing the opportunity to check whether or not such vigorous vertical transport mechanisms are sufficiently captured by common flux measurement techniques (Mayer et al., 2008), e.g. the eddy-covariance (EC) method. To sum up, this study demonstrates the profound quality assurance and control effort adapted to the energy exchange measurements and its applicability to the selection and description of free convection events (FCEs).