Dynamical Perspectives on the Formation and Intensification of Polar Lows
This thesis consists of a collection of scientific publications addressing dynamical aspects of the formation and intensification of polar lows. Polar lows are small scale, intense, short-lived cyclones developing over ice-free oceans at high latitudes. In the first paper, environmental atmospheric...
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The University of Bergen
2014
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ftunivbergen:oai:bora.uib.no:1956/8987 2023-05-15T14:27:46+02:00 Dynamical Perspectives on the Formation and Intensification of Polar Lows Terpstra, Annick 2014-11-25 application/pdf https://hdl.handle.net/1956/8987 eng eng The University of Bergen Paper I: Annick Terpstra, Clio Michel, Thomas Spengler, Atmospheric environments associated with polar low genesis in the North-East Atlantic. Full text not available in BORA. Paper II: Annick Terpstra, Thomas Spengler, A novel method to initialize idealized channel simulations, Montly Weather Review. Full text not available in BORA. Paper III: Annick Terpstra, Thomas Spengler, Richard Moore, Idealised simulations of polar low development in an Arctic moist-baroclinic environment, Quarterly Journal of the Royal Meteorological Society. Full text not available in BORA. urn:isbn:978-82-308-2797-0 https://hdl.handle.net/1956/8987 cristin:1174566 Copyright the author. All rights reserved Doctoral thesis 2014 ftunivbergen 2023-03-14T17:44:17Z This thesis consists of a collection of scientific publications addressing dynamical aspects of the formation and intensification of polar lows. Polar lows are small scale, intense, short-lived cyclones developing over ice-free oceans at high latitudes. In the first paper, environmental atmospheric conditions during polar low genesis are identified. These environmental conditions are classified based on the direction between the thermal wind and the mean flow in the lower troposphere. If the thermal wind and mean flow are in opposite direction the environment is classified as reverse shear, if they are in the same direction the environment is classified as forward shear. The two types of pre-polar low environments exhibit distinctly different features in terms of synoptic scale patterns, baroclinicity, configurations of sea surface temperature, depth and stratification of the troposphere, polar low propagation directions, and surface fluxes. The ambient polar low environment during forward shear conditions resembles typical mid-latitude baroclinic cyclogenesis, whereas the reverse shear conditions are characterized by the presence of a synoptic scale, occluded low over the genesis location, and a strong low-level jet. In the second paper, a method to initialize baroclinic channel models is devised. The initial conditions are hydrostatically and geostrophically balanced, which makes them particularly suitable for studying rapid cyclogenesis. Furthermore, the method allows the definition of an arbitrary windfield, hence the initialization method exhibits a large degree of freedom in defining the initial conditions. We performed an unperturbed simulation which features minimal gravity wave activity, illustrating the balanced initial conditions. We also performed a perturbed simulation to examplify the utility of the setup. In this simulation baroclinic instability is triggered resulting in perturbation growth with time- and length-scales in agreement with observed polar low development. In the third paper, an ... Doctoral or Postdoctoral Thesis Arctic University of Bergen: Bergen Open Research Archive (BORA-UiB) |
institution |
Open Polar |
collection |
University of Bergen: Bergen Open Research Archive (BORA-UiB) |
op_collection_id |
ftunivbergen |
language |
English |
description |
This thesis consists of a collection of scientific publications addressing dynamical aspects of the formation and intensification of polar lows. Polar lows are small scale, intense, short-lived cyclones developing over ice-free oceans at high latitudes. In the first paper, environmental atmospheric conditions during polar low genesis are identified. These environmental conditions are classified based on the direction between the thermal wind and the mean flow in the lower troposphere. If the thermal wind and mean flow are in opposite direction the environment is classified as reverse shear, if they are in the same direction the environment is classified as forward shear. The two types of pre-polar low environments exhibit distinctly different features in terms of synoptic scale patterns, baroclinicity, configurations of sea surface temperature, depth and stratification of the troposphere, polar low propagation directions, and surface fluxes. The ambient polar low environment during forward shear conditions resembles typical mid-latitude baroclinic cyclogenesis, whereas the reverse shear conditions are characterized by the presence of a synoptic scale, occluded low over the genesis location, and a strong low-level jet. In the second paper, a method to initialize baroclinic channel models is devised. The initial conditions are hydrostatically and geostrophically balanced, which makes them particularly suitable for studying rapid cyclogenesis. Furthermore, the method allows the definition of an arbitrary windfield, hence the initialization method exhibits a large degree of freedom in defining the initial conditions. We performed an unperturbed simulation which features minimal gravity wave activity, illustrating the balanced initial conditions. We also performed a perturbed simulation to examplify the utility of the setup. In this simulation baroclinic instability is triggered resulting in perturbation growth with time- and length-scales in agreement with observed polar low development. In the third paper, an ... |
format |
Doctoral or Postdoctoral Thesis |
author |
Terpstra, Annick |
spellingShingle |
Terpstra, Annick Dynamical Perspectives on the Formation and Intensification of Polar Lows |
author_facet |
Terpstra, Annick |
author_sort |
Terpstra, Annick |
title |
Dynamical Perspectives on the Formation and Intensification of Polar Lows |
title_short |
Dynamical Perspectives on the Formation and Intensification of Polar Lows |
title_full |
Dynamical Perspectives on the Formation and Intensification of Polar Lows |
title_fullStr |
Dynamical Perspectives on the Formation and Intensification of Polar Lows |
title_full_unstemmed |
Dynamical Perspectives on the Formation and Intensification of Polar Lows |
title_sort |
dynamical perspectives on the formation and intensification of polar lows |
publisher |
The University of Bergen |
publishDate |
2014 |
url |
https://hdl.handle.net/1956/8987 |
genre |
Arctic |
genre_facet |
Arctic |
op_relation |
Paper I: Annick Terpstra, Clio Michel, Thomas Spengler, Atmospheric environments associated with polar low genesis in the North-East Atlantic. Full text not available in BORA. Paper II: Annick Terpstra, Thomas Spengler, A novel method to initialize idealized channel simulations, Montly Weather Review. Full text not available in BORA. Paper III: Annick Terpstra, Thomas Spengler, Richard Moore, Idealised simulations of polar low development in an Arctic moist-baroclinic environment, Quarterly Journal of the Royal Meteorological Society. Full text not available in BORA. urn:isbn:978-82-308-2797-0 https://hdl.handle.net/1956/8987 cristin:1174566 |
op_rights |
Copyright the author. All rights reserved |
_version_ |
1766301678742536192 |