Can Mountain Waves Contribute to Damaging Winds Far Away from the Lee Slope?
Can Mountain Waves Contribute to Damaging Winds Far Away from the Lee Slope?
复制标题
远离李坡的山浪会带来破坏性的风吗？
DOI：
10.1175/waf-d-18-0207.1
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发表时间：
2019
影响因子：
2.9
通讯作者：
Durran, Dale R.
中科院分区：
文献类型：
--
作者：
Kelley, Jeffrey D.;Schultz, David M.;Schumacher, Russ S.;Durran, Dale R.
2016年12月25日，一个984百帕的气旋离开科罗拉多并进入北方平原，附近的北极锋被卷入环流，并以气旋方式环绕气旋的赤道方向。一条宽130公里、长850公里、风速超过25 m s− 1的地面风带起源于背风气旋的逗点下方，沿着北极锋的路径从科罗拉多到明尼苏达州。这些强风与科罗拉多和怀俄明州上空的下坡风暴和山浪共同形成，产生了高空急流。在这种情况下，风的分布的中心是北极气团，它既保护了升高的风免受锋面后面的表面摩擦，又促进了升高的急流混合到北极锋面后面的表面，这是由于与冷空气平流相关的陡峭的直减率。气旋中心以南的强烈环流将北极锋和高空急流带离山脉，穿越大平原。2012年2月28日至29日，一场类似的气旋发生了下坡风暴，但由于缺乏明确的北极锋和锋后稳定层，没有形成表面中尺度风最大值。尽管这种表面风最大值与刺式喷流（例如，起源于对流层中部气旋的逗点头内，下降蒸发逗点头，加速到边界层顶部，并与冷传送带分开存在），这条风不是由刺痛射流引起的。
On 25 December 2016, a 984-hPa cyclone departed Colorado and moved onto the northern plains, drawing a nearby Arctic front into the circulation and wrapping it cyclonically around the equatorward side of the cyclone. A 130-km-wide and 850-km-long swath of surface winds exceeding 25 m s−1originated underneath the comma head of the lee cyclone and followed the track of the Arctic front from Colorado to Minnesota. These strong winds formed in association with a downslope windstorm and mountain wave over Colorado and Wyoming, producing an elevated jet of strong winds. Central to the distribution of winds in this case is the Arctic air mass, which both shielded the elevated winds from surface friction behind the front and facilitated the mixing of the elevated jet down to the surface just behind the Arctic front, due to steep lapse rates associated with cold-air advection. The intense circulation south of the cyclone center transported the Arctic front and the elevated jet away from the mountains and out across Great Plains. This case is compared to an otherwise similar cyclone that occurred on 28–29 February 2012 in which a downslope windstorm occurred, but no surface mesoscale wind maximum formed due to the absence of a well-defined Arctic front and postfrontal stable layer. Despite the superficial similarities of this surface wind maximum to a sting jet (e.g., origin in the midtroposphere within the comma head of the cyclone, descent evaporating the comma head, acceleration to the top of the boundary layer, and an existence separate from the cold conveyor belt), this swath of winds was not caused by a sting jet.