Characteristics of the early-morning shallow convective boundary layer from Helipod Flights during STINHO-2
Characteristics of the early-morning shallow convective boundary layer from Helipod Flights during STINHO-2
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STINHO-2期间直升机飞行的清晨浅对流边界层特征
DOI：
10.1007/s00704-006-0272-2
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发表时间：
2007
影响因子：
3.4
通讯作者：
A. J. van den Kroonenberg
中科院分区：
文献类型：
--
作者：
J. Bange;T. Spiess;A. J. van den Kroonenberg
摘要 使用直升机探测器 Helipod 进行了早晨过渡期间浅对流边界层 (SCBL) 的空气湍流测量。该实验是在 STINHO-2 夏季运动期间在异质陆地表面进行的。当早上 SCBL 的最高点迅速上升时，直升机进行直线和水平飞行。通过这种飞行策略，获得了相对于 zi 的水平平均边界层特性的垂直剖面。 5 公里的直线水平飞行时间足够短，足以提供低层大气的快照。在逆温层烧毁期间，残余夜间逆温层的位温保持不变。 SCBL深度、表面温度和表面热通量随时间的增加可以通过线性近似很好地描述。由于涡旋翻转时间短，预计 SCBL 会产生良好的垂直混合。然而，地表上方约 100 米处的热通量表现出较大的线性时间行为偏差。应用迪尔多夫缩放方案，发现经典白天对流边界层 (CBL) 热通量分布周围存在大的分散。无量纲热通量在约 0.6 zi 处过零，得出平均夹带参数为 0.83。夹带被认为是 SCBL 生长最重要的机制。无量纲统计离散度与白天 CBL 存在显着差异。
SummaryAirborne turbulence measurements in the shallow convective boundary layer (SCBL) during the morning transition were performed using the helicopter probe Helipod. The experiment was carried out during the STINHO-2 summer campaign over heterogeneous land surface. While the top zi of the morning SCBL was rapidly rising, the Helipod performed straight and level flights. With this flight strategy, vertical profiles of horizontally averaged boundary-layer properties with respect to zi were obtained. The time to fly the 5 km straight and level legs was short enough to provide snapshots of the lower atmosphere. During the burning-off of the inversion layer the potential temperature in the residual nocturnal inversion layer remained unchanged. The increase of the SCBL depth, the surface temperature and the surface heat flux in time could be well described by a linear approximation. Due to a short eddy-overturning time a good vertical mixing of the SCBL was expected. However, the heat flux at about 100 m above the surface exhibited larger deviation from linear temporal behaviour. Applying the Deardorff scaling scheme, large scatter around the classic daytime convective boundary layer (CBL) heat flux profile was found. The dimensionless heat flux crossed zero at about 0.6 zi and a mean entrainment parameter of 0.83 was derived. Entrainment was rated to be the most important mechanism for SCBL growth. Significant difference to the daytime CBL was found regarding the dimensionless statistical dispersions.