Structure of a shear-line polar low
Structure of a shear-line polar low
复制标题
切变线极地低压的结构
DOI：
10.1002/qj.2911
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发表时间：
2016
影响因子：
8.9
通讯作者：
Sergeev D
中科院分区：
文献类型：
--
作者：
Sergeev D
2013年3月期间，一系列极地低压起源于一个高涡度（>10−3s−1）切变带，这与挪威海上空一场持续的海洋冷空气爆发有关。使用来自仪器齐全的飞机，下投式探空仪，散射仪和CloudSat数据的综合观测，以及Met Office统一模型对流解析配置的数值模拟输出，对爆发前沿的一个切变线极地低压进行了详细分析。穿过切变线的最大低空风梯度为50公里范围内的25 m s− 1。北面和西面的强风位于冷空气团内，并伴随着大量的地表湍流热通量和对流云。切变线以南和以东的低风速与低热量通量和极地低压中的清晰“眼睛”有关。剪切线中伽马尺度不稳定性合并到极低似乎对其结构和发展很重要。模式很好地捕捉到了切变线和极低层结构，特别是水平切变和中尺度热力场的强度。极地低气压周围对流云带的空间结构模拟得相当好，但与观测结果相比，模型明显低估了云层的液态水含量和高度。切变线极低是相对常见的，然而这种情况可以说是第一次被广泛的原位和远程观测与数值模式输出相结合。
During March 2013 a series of polar lows originated in a high‐vorticity (>10−3s−1) shear zone that was associated with a prolonged marine cold‐air outbreak over the Norwegian Sea. A detailed analysis of one shear‐line polar low at the leading edge of the outbreak is presented using comprehensive observations from a well‐instrumented aircraft, dropsondes, scatterometer and CloudSat data, and numerical modelling output from a convection‐resolving configuration of the Met Office Unified Model. The maximum low‐level wind gradient across the shear line was 25 m s−1over 50 km. High winds to the north and west were within the cold air mass and were associated with large surface turbulent heat fluxes and convective clouds. Low wind speeds to the south and east of the shear line were associated with low heat fluxes and a clear ‘eye’ in the polar low. Shear‐line meso‐gamma‐scale instabilities merging into the polar low appeared important to its structure and development. The model captured the shear line and the polar low structure very well–in particular the strength of the horizontal shear and the mesoscale thermodynamic fields. The spatial structure of convective cloud bands around the polar low was simulated reasonably well, but the model significantly underestimated the liquid water content and height of the cloud layers compared to the observations. Shear‐line polar lows are relatively common, however this case is arguably the first to be examined with a wide range ofin situand remote observations allied with numerical model output.