Structure of a shear-line polar low

Sergeev, D. E., Renfrew, I. A., Spengler, T. and Dorling, S. R. (2017) Structure of a shear-line polar low. Quarterly Journal of the Royal Meteorological Society, 143 (702). 12–26. ISSN 0035-9009

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Abstract

During March 2013 a series of polar lows originated in a high-vorticity (>10−3 s−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−1 over 50 km. High windsto the north and west were within the cold-air mass and were associated with large surface turbulent heat fluxes and convective clouds. Low wind speed to the south and east of the shear line were associated with low heat fluxes and a clear ‘eye’ in the polarlow. Shear-line meso-γ-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 spatialstructure of convective cloud bands around the polar low wassimulated reasonably well, but the modelsignificantly 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 of in-situ and remote observations allied with numerical model output.

Item Type: Article
Additional Information: © 2016 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Uncontrolled Keywords: polar low,shear line,norwegian sea,aircraft observations,cloudsat,met office unified model
Faculty \ School: Faculty of Science
Faculty of Science > School of Environmental Sciences
Depositing User: Pure Connector
Date Deposited: 23 Sep 2016 11:44
Last Modified: 24 Nov 2020 00:59
URI: https://ueaeprints.uea.ac.uk/id/eprint/59685
DOI: 10.1002/qj.2911

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