Modelling and parametrization of the convective flow over leads in sea ice and comparison with airborne observations

A non‐eddy‐resolving microscale model is applied to simulate convection over three different leads (elongated channels in sea ice), which were observed by aircraft over the Arctic Marginal Ice Zone in 2013. The study aims to evaluate the quality of a local and a non‐local turbulence parametrization....

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Main Authors: Michaelis, Janosch, Lüpkes, Christof, Schmitt, Amelie U., Hartmann, Jörg
Format: Text
Language:English
Published: John Wiley & Sons, Ltd 2021
Subjects:
Online Access:https://dx.doi.org/10.23689/fidgeo-4402
https://e-docs.geo-leo.de/handle/11858/8748
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spelling ftdatacite:10.23689/fidgeo-4402 2023-05-15T15:06:51+02:00 Modelling and parametrization of the convective flow over leads in sea ice and comparison with airborne observations Michaelis, Janosch Lüpkes, Christof Schmitt, Amelie U. Hartmann, Jörg 2021 https://dx.doi.org/10.23689/fidgeo-4402 https://e-docs.geo-leo.de/handle/11858/8748 en eng John Wiley & Sons, Ltd Text Article article-journal ScholarlyArticle 2021 ftdatacite https://doi.org/10.23689/fidgeo-4402 2021-11-05T12:55:41Z A non‐eddy‐resolving microscale model is applied to simulate convection over three different leads (elongated channels in sea ice), which were observed by aircraft over the Arctic Marginal Ice Zone in 2013. The study aims to evaluate the quality of a local and a non‐local turbulence parametrization. The latter represents a lead‐width‐dependent approach for the turbulent fluxes designed for idealised conditions of a lead‐perpendicular, near‐neutral inflow in an atmospheric boundary layer (ABL) capped by a strong inversion at around 250 to 350 m height. The observed cases considered here are also characterised by an almost lead‐perpendicular flow but, in comparison to the idealised conditions, our analysis covers effects in stable inflow conditions and a much shallower ABL. The model simulations are initialised with observed surface parameters and upwind profiles, and the results are compared with measurements obtained above and downwind of the leads. The basic observed features related to the lead‐generated convection can be reproduced with both closures, but the observed plume inclination and vertical entrainment near the inversion layer by the penetrating plume are underestimated. The advantage of the non‐local closure becomes obvious by the more realistic representation of regions with observed vertical entrainment or where the observations hint at counter‐gradient transport. It is shown by comparison with the observations that results obtained with the non‐local closure can be further improved by including the determination of a fetch‐dependent inversion height and by specifying a parameter determining the plume inclination as a function of the upwind ABL stratification. Both effects improve the representation of fluxes, boundary‐layer warming, and vertical entrainment. The model is also able to reproduce the observed vanishing of a weak low‐level jet over the lead, but its downwind regeneration and related momentum transport are not always well captured, irrespective of the closure used. : In typical springtime conditions of a cold atmospheric flow over the warm surfaces of leads, which are open‐water channels in sea ice, strong convective plumes are generated which have a large impact on atmospheric boundary‐layer characteristics. Here, a small‐scale model is applied to simulate such situations and model results obtained with different turbulence parametrizations are evaluated using airborne measurements. Based on the observations, a non‐local parametrization developed for the small‐scale modelling of the inhomogeneous convection over leads is further improved. : Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) via the Transregional Collaborative Research Center ArctiC Amplification (AC)3 (project number 268020496 TRR 172) and via the priority program SPP 1158 (grant LU 818/5‐1) Text Arctic Sea ice DataCite Metadata Store (German National Library of Science and Technology) Arctic
institution Open Polar
collection DataCite Metadata Store (German National Library of Science and Technology)
op_collection_id ftdatacite
language English
description A non‐eddy‐resolving microscale model is applied to simulate convection over three different leads (elongated channels in sea ice), which were observed by aircraft over the Arctic Marginal Ice Zone in 2013. The study aims to evaluate the quality of a local and a non‐local turbulence parametrization. The latter represents a lead‐width‐dependent approach for the turbulent fluxes designed for idealised conditions of a lead‐perpendicular, near‐neutral inflow in an atmospheric boundary layer (ABL) capped by a strong inversion at around 250 to 350 m height. The observed cases considered here are also characterised by an almost lead‐perpendicular flow but, in comparison to the idealised conditions, our analysis covers effects in stable inflow conditions and a much shallower ABL. The model simulations are initialised with observed surface parameters and upwind profiles, and the results are compared with measurements obtained above and downwind of the leads. The basic observed features related to the lead‐generated convection can be reproduced with both closures, but the observed plume inclination and vertical entrainment near the inversion layer by the penetrating plume are underestimated. The advantage of the non‐local closure becomes obvious by the more realistic representation of regions with observed vertical entrainment or where the observations hint at counter‐gradient transport. It is shown by comparison with the observations that results obtained with the non‐local closure can be further improved by including the determination of a fetch‐dependent inversion height and by specifying a parameter determining the plume inclination as a function of the upwind ABL stratification. Both effects improve the representation of fluxes, boundary‐layer warming, and vertical entrainment. The model is also able to reproduce the observed vanishing of a weak low‐level jet over the lead, but its downwind regeneration and related momentum transport are not always well captured, irrespective of the closure used. : In typical springtime conditions of a cold atmospheric flow over the warm surfaces of leads, which are open‐water channels in sea ice, strong convective plumes are generated which have a large impact on atmospheric boundary‐layer characteristics. Here, a small‐scale model is applied to simulate such situations and model results obtained with different turbulence parametrizations are evaluated using airborne measurements. Based on the observations, a non‐local parametrization developed for the small‐scale modelling of the inhomogeneous convection over leads is further improved. : Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) via the Transregional Collaborative Research Center ArctiC Amplification (AC)3 (project number 268020496 TRR 172) and via the priority program SPP 1158 (grant LU 818/5‐1)
format Text
author Michaelis, Janosch
Lüpkes, Christof
Schmitt, Amelie U.
Hartmann, Jörg
spellingShingle Michaelis, Janosch
Lüpkes, Christof
Schmitt, Amelie U.
Hartmann, Jörg
Modelling and parametrization of the convective flow over leads in sea ice and comparison with airborne observations
author_facet Michaelis, Janosch
Lüpkes, Christof
Schmitt, Amelie U.
Hartmann, Jörg
author_sort Michaelis, Janosch
title Modelling and parametrization of the convective flow over leads in sea ice and comparison with airborne observations
title_short Modelling and parametrization of the convective flow over leads in sea ice and comparison with airborne observations
title_full Modelling and parametrization of the convective flow over leads in sea ice and comparison with airborne observations
title_fullStr Modelling and parametrization of the convective flow over leads in sea ice and comparison with airborne observations
title_full_unstemmed Modelling and parametrization of the convective flow over leads in sea ice and comparison with airborne observations
title_sort modelling and parametrization of the convective flow over leads in sea ice and comparison with airborne observations
publisher John Wiley & Sons, Ltd
publishDate 2021
url https://dx.doi.org/10.23689/fidgeo-4402
https://e-docs.geo-leo.de/handle/11858/8748
geographic Arctic
geographic_facet Arctic
genre Arctic
Sea ice
genre_facet Arctic
Sea ice
op_doi https://doi.org/10.23689/fidgeo-4402
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