Aircraft Observations Of The Mean And Turbulent Structure Of A Shallow Boundary Layer Over The Persian Gulf
Aircraft Observations Of The Mean And Turbulent Structure Of A Shallow Boundary Layer Over The Persian Gulf
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飞机对波斯湾浅边界层平均和湍流结构的观测
DOI：
10.1023/a:1002623712237
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发表时间：
2000
影响因子：
4.3
通讯作者：
D. Rogers
中科院分区：
文献类型：
--
作者：
I. Brooks;D. Rogers
稳定的内部边界层形成时，温暖的空气平流在较冷的表面，一个常见的发生在沿海地区。内边界层随顺风向距离的增加而加深，最终与表面达到平衡，成为一个充分发展的海洋边界层。我们介绍了英国对内边界层演化后期的观测结果。1996年4月，气象局的C-130大力神研究飞机飞越波斯湾。西北风将温暖的干燥空气从周围的沙漠陆地带到墨西哥湾的生态沃茨。热量流失到表面导致在海岸顺风处形成了一个浅而稳定的内部边界层。飞机测量是在下风向几百公里处进行的，此时原来的深对流边界层已经被侵蚀掉，内部边界层发展得很好，实际上是一个新的海洋大气边界层。在边界层的大部分深度上，边界层是静态稳定的，向下的热通量约为15 W m-2;然而，一个异常强潜热通量，在近表面超过250 W m-2，足以克服向下的热通量，并在边界层下部30 -50%的区域维持弱的浮力对流。层湍流统计使用局部相似理论产生的结果与以前的研究。然而，由于湿度对浮力通量的贡献很大，所以在相似尺度的定义上需要注意。通常在温度和长度尺度的定义中使用感热或浮力通量;后者用于湿度在确定稳定性方面起重要作用的水域。在目前的情况下，我们发现，虽然浮力通量是适当的定义的长度尺度，温度scalemust定义的感热通量。
Stable internal boundary layers form when warm air isadvected over a cooler surface, a common occurrence incoastal areas. The internal boundary layer deepenswith distance along-wind, eventually reachingequilibrium with the surface and becoming a fullydeveloped marine boundary layer. We presentobservations of the late stages of internalboundary-layer evolution made bythe U.K. Meteorological Office'sC-130 Hercules research aircraft over the Persian Gulfin April 1996. Northwesterly winds brought warm dryair from the surrounding desert landmass across thecooler waters of the Gulf. Loss of heat to the surfaceresulted in the formation of a shallow, stableinternal boundary layer downwind of the coast. The aircraftmeasurements were made several hundred kilometresdownwind, by which point the original deep convectiveboundary layer had been eroded away and the internalboundary layer was well developed, effectively a newmarine atmospheric boundary layer. Throughout most ofits depth the boundary layer was statically stable anda downward heat flux of approximately 15 W m-2was observed; however, an exceptionally strong latentheat flux, in excess of 250 W m-2 near thesurface, was sufficient to overcome the downwards heatflux and maintain weak buoyant convection in the lower30–50% of the boundary layer.Scaling of boundary-layer turbulence statistics usinglocal similarity theory produces results in agreementwith previous studies. Because of the strong humiditycontribution to the buoyancy flux, however, care isrequired with the definition of the similarity scales.It is usual for either the sensible heat or buoyancyflux to be used in the definitions of both thetemperature and length scales; the latter being usedover water where humidity plays a significant role indetermining stability. In the present case we findthat while the buoyancy flux is appropriate in thedefinition of the length scale, the temperature scalemust be defined in terms of the sensible heat flux.