Dynamical Processes in the Arctic Atmosphere

Jonassen, Marius O.; Chechin, Dmitry; Karpechko, Alexey Yu.; Lüpkes, Christof; Spengler, Thomas; Tepstra, Annick; Vihma, Timo; Zhang, Xiangdong

doi:10.1007/978-3-030-33566-3_1

Cited by 6 publications

(6 citation statements)

References 231 publications

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“…The patterns, also referred to as nodes, are ordered in a two-dimensional array with neighbouring nodes being more similar to each other than nodes further apart in the array. Kohonen (2001) originally developed the method for artificial neural networks, but in recent years it has been extensively applied in many fields of science, including climate data analysis (e.g. Nygård et al, 2019).…”

Section: Self-organising Maps (Soms)mentioning

confidence: 99%

“…Rasmussen, 1979;Emanuel and Rotunno, 1989). The multitude of paradigms demonstrates that our dynamical interpretation of these systems is still deficient (Jonassen et al, 2020). To further alleviate this shortcoming, we present a classification of PLs by their structure and sub-synoptic environment to identify the relevance of the proposed paradigms.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, hurricane-like PLs rarely resemble the structure of hurricanes; instead they feature asymmetric updrafts typical of baroclinic development with latent heating not playing the dominant role (Føre et al, 2012;Kolstad et al, 2016;Kolstad and Bracegirdle, 2017). The PLs that appear hurricane-like in their mature stage appear to be initiated by baroclinic instability (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Polar lows – moist-baroclinic cyclones developing in four different vertical wind shear environments

Stoll

Spengler

Terpstra

et al. 2021

Weather Clim. Dynam.

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Abstract. Polar lows are intense mesoscale cyclones that develop in polar marine air masses. Motivated by the large variety of their proposed intensification mechanisms, cloud structure, and ambient sub-synoptic environment, we use self-organising maps to classify polar lows. The method is applied to 370 polar lows in the north-eastern Atlantic, which were obtained by matching mesoscale cyclones from the ERA-5 reanalysis to polar lows registered in the STARS dataset by the Norwegian Meteorological Institute. ERA-5 reproduces most of the STARS polar lows. We identify five different polar-low configurations which are characterised by the vertical wind shear vector, the change in the horizontal-wind vector with height, relative to the propagation direction. Four categories feature a strong shear with different orientations of the shear vector, whereas the fifth category contains conditions with weak shear. This confirms the relevance of a previously identified categorisation into forward- and reverse-shear polar lows. We expand the categorisation with right- and left-shear polar lows that propagate towards colder and warmer environments, respectively. For the strong-shear categories, the shear vector organises the moist-baroclinic dynamics of the systems. This is apparent in the low-pressure anomaly tilting with height against the shear vector and the main updrafts occurring along the warm front located in the forward-left direction relative to the shear vector. These main updrafts contribute to the intensification through latent heat release and are typically associated with comma-shaped clouds. Polar-low situations with a weak shear, which often feature spirali-form clouds, occur mainly at decaying stages of the development. We thus find no evidence for hurricane-like intensification of polar lows and propose instead that spirali-form clouds are associated with a warm seclusion process.

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Section: Self-organising Maps (Soms)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Polar lows – moist-baroclinic cyclones developing in four different vertical wind shear environments

Stoll

Spengler

Terpstra

et al. 2021

Weather Clim. Dynam.

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“…Such strong wind is known to be enhanced at the mesoscale when stably stratified flow impinges on and is forced to flow along mountains, forming a phenomenon known as barrier flow (e.g. Jonassen et al., 2020). The wind field along the slopes in the region (Figure 3) does resemble barrier flow during strong synoptic flow induced by mechanism 2 under the situations with the strongest winds (see also Figures and ).…”

Section: Resultsmentioning

confidence: 99%

Evaluation of Three Numerical Weather Prediction Models for the Weddell Sea Region for the Austral Winter 2013

2021

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The performance of numerical weather prediction (NWP) systems is generally poorer at higher latitudes compared to other regions (e.g. Jung et al., 2016). This is due to various reasons, including scarcity of in situ observations and challenges related to utilization of satellite remote sensing observations, such as the polar night, lack of data from geostationary satellites, and difficulties in interpreting microwave signals originating from snow, ice, and clouds (Scarlat et al., 2018). Other reasons are complexity of surface boundary conditions due to rapidly changing sea ice concentration (Valkonen et al., 2014), rapidly developing mesoscale systems, such as polar lows and explosive cyclones (Pezza et al., 2016), and complexity of subgrid-scale physical processes related, among others, to stable boundary layer (Nigro et al., 2017), mixed-phase clouds

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“…Previous studies have shown that the formation of PLs is associated with favorable environmental conditions, including reduced static stability and enhanced low‐level baroclinicity (e.g., Jonassen et al., 2020; Kolstad, 2011; Rasmussen and Turner, 2003; Stoll et al., 2021). The former is associated with marine cold air outbreaks (MCAOs; Kolstad et al., 2009), while the latter is closely tied to coastlines and sea‐ice margins and is modulated by the thermodynamic properties of local air masses (e.g., Serreze et al., 2001).…”

Section: Introductionmentioning

confidence: 99%

Modulation of Polar Low Activity by the Madden‐Julian Oscillation

Wang

Boyd

Walsh

2023

Geophysical Research Letters

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Polar lows (PLs) are intense mesoscale cyclones that form over high-latitude oceans (Rasmussen and Turner, 2003). They are characterized by intense surface winds and can produce heavy precipitation, strong icing, low visibility, and large ocean waves (Harrold & Browning, 1969;Orimolade et al., 2016;Samuelsen et al., 2015), posing hazards to high-latitude coastal communities and marine operations. However, it is challenging for global models to realistically represent or skillfully predict PLs due to their small scale (with a typical diameter of 200-500 km), short lifetime (typically <48 hr), and convective nature (e.g.

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Dynamical Processes in the Arctic Atmosphere

Cited by 6 publications

References 231 publications

Polar lows – moist-baroclinic cyclones developing in four different vertical wind shear environments

Polar lows – moist-baroclinic cyclones developing in four different vertical wind shear environments

Evaluation of Three Numerical Weather Prediction Models for the Weddell Sea Region for the Austral Winter 2013

Modulation of Polar Low Activity by the Madden‐Julian Oscillation

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