Characterisation of valley flows within two confluent valleys under stable conditions: observations from the KASCADE field experiment
Characterisation of valley flows within two confluent valleys under stable conditions: observations from the KASCADE field experiment
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稳定条件下两个汇合山谷内山谷流的特征：KASCADE 现场实验的观察结果
DOI：
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
M. Fourmentin
中科院分区：
文献类型：
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作者：
G. Duine;T. Hedde;P. Roubin;P. Durand;M. Lothon;F. Lohou;P. Augustin;M. Fourmentin
主要和支流流域系统的风型经历了日变化，这种变化非常依赖于山谷的大小。确定河谷下游风的特征对于污染物扩散研究是重要的，也是数值模拟的一个挑战。本文利用KASCADE(卡达拉奇风速和稳定性)观测资料，描述了法国东南部前阿尔卑斯山地区两个大小不同的相交浅山谷中向下流动的发展和特征。杜兰斯山谷和它的支流卡达拉奇山谷在深度(200米比100米)、坡度(0.2米比1.2米)、宽度(5到8米比1到2公里)和长度(50比6公里)上都不同。在测量期间，这两种向下流动都是主要特征。不同的河谷尺度导致了不同的特征：较小的卡达拉奇下谷风主要是热驱动的，风速可达1-4m S-1，喷流鼻子高度约为30m。在该高度的流动开始于感热通量翻转后2小时，这一时间尺度与沿谷风的线性波解有关。Durance下谷风涉及更大的尺度--无论是地形特征还是大尺度环流--与山区到平原的环流有关，因此它的发生在日落后延迟6小时。它的速度为4-8m S-1，深度为175-225m a.g.l。它的最高出现时间是在日出后。在两个谷风之间，观察到一个切变层，其起源可能是由地形改变方向的卡达拉奇谷流回流和杜兰斯谷下风流的组合。
The wind patterns in main and tributary valley systems undergo diurnal variation that are very dependent on the valleys dimensions. Characterising the down-valley winds is important for pollutant dispersion studies and a challenge for numerical simulations. This paper uses the KASCADE (KAtabatic winds and Stability over CAdarache for Dispersion of Effluents) observations to describe down-valley flow development and characteristics in two intersecting, shallow valleys of different size located in the prealpine region of southeastern France. The Durance Valley and its tributary valley, the Cadarache Valley, are different in depth (200 vs. 100 m depth, respectively), slope (0.2 vs. 1.2 ), width (5 to 8 vs. 1 to 2 km) and length ( > 50 vs. 6 km). Both down-valley flows were dominant features for the period of measurements. The distinct valley scales lead to different characteristics: the smaller Cadarache down-valley wind is primarily thermally driven and attains wind speeds up to 1 - 4 m s -1 with its jet nose at around 30 m height a.g.l. The flow at that height initiates 2 hours after sensible heat flux turnover, a timescale that relates to linear wave solution for along-valley winds. The Durance down-valley wind involves larger scales - for both terrain features and large-scale circulation -, is related to a mountain-to-plain circulation and therefore its onset occurs with a delay of 6 hours after sunset. It reaches speeds of 4 - 8 m s -1 and a depth of 175 - 225 m a.g.l. Its highest occurrence is just after sunrise. In between the two valley winds, a shear layer is observed whose origin could be a combination of a Cadarache valley flow return current and a Durance down-valley wind stream re-directed by orography.