The full life cycle of a polar low over the Norwegian Sea observed by three research aircraft flights

Føre, Ivan; Kristjánsson, Jón Egill; Sætra, Øyvind; Breivik, Øyvind; Røsting, Bjørn; Shapiro, M. A.

doi:10.1002/qj.825

Cited by 34 publications

(54 citation statements)

References 33 publications

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“…In an observational study of a mesoscale cyclone southeast of Greenland, McInnes et al (2009) found by carrying out PV inversion that a similar dry slot was a strong indication of upper-level forcing. An analysis performed by Føre et al (2011) indicates that both low-level baroclinic instability and upper-level forcing contributed to the development of the polar low. However, in order to explain why we get a better simulation of this cyclone when we run the model at 4 and 1 km grid spacing instead of 12 km, it would be useful to pay attention to convection and latent heating.…”

Section: Discussionmentioning

confidence: 99%

The role of horizontal resolution for polar low simulations

McInnes

Kristiansen

Kristjánsson

et al. 2011

Quart J Royal Meteoro Soc

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Polar lows are intense mesoscale cyclones that mainly occur during the winter over the sea in polar regions. Owing to their small spatial scale with a diameter between 200 and 1000 km, simulating polar lows is a challenging task. In this study we investigated how increased resolution of a numerical weather prediction model impacts its ability to simulate polar lows. We focused on a polar low that was successfully captured by three different flights during the IPY-THORPEX field campaign in 2008. Verifying model results against campaign data showed that decreasing the horizontal grid spacing from 12 to 4 km significantly improved the simulation of the developing polar low, and a further decrease to 1 km gave further improvement. A model run with latent heating reduced to 10% indicated an extensive influence of diabatic heating in this polar low case, and we suggest that the improved model performance at higher resolution could be connected to the model's handling of convection. Additional simulations starting 24 h later showed that the initial conditions were important for the model performance, and when simulating another polar low case we found that the model failed to produce the polar low independent of the resolution. This shows that while higher resolution indeed may give improved predictions of polar lows, other factors like synoptic situation, lateral boundaries and the initial condition may also be important.

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Section: Discussionmentioning

confidence: 99%

The role of horizontal resolution for polar low simulations

McInnes

Kristiansen

Kristjánsson

et al. 2011

Quart J Royal Meteoro Soc

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“…Linders and Saetra, 2010;Føre et al, 2011;Føre and Nordeng, 2012;McInnes et al, 2011;Wagner et al, 2011;Irvine et al, 2011;Aspelien et al, 2011;Kristiansen et al, 2011). Finding, for example, that this case had critical upper-level forcing (Føre et al, 2011), and was more accurately simulated with a convection-permitting grid resolution of 4 or 1 km (McInnes et al, 2011). Operational weather forecasting systems have now reached the state where polar lows should be able to be predicted routinely.…”

Section: Mesoscale Cyclonesmentioning

confidence: 95%

“…In the latter, arguably the most comprehensive set of observations of a polar low to date were obtained for a case over the northern Norwegian Sea, enabling studies of the structure, dynamics, lifecycle, simulation accuracy, and predictability of this event (e.g. Linders and Saetra, 2010;Føre et al, 2011;Føre and Nordeng, 2012;McInnes et al, 2011;Wagner et al, 2011;Irvine et al, 2011;Aspelien et al, 2011;Kristiansen et al, 2011). Finding, for example, that this case had critical upper-level forcing (Føre et al, 2011), and was more accurately simulated with a convection-permitting grid resolution of 4 or 1 km (McInnes et al, 2011).…”

Section: Mesoscale Cyclonesmentioning

confidence: 99%

Advances in understanding and parameterization of small-scale physical processes in the marine Arctic climate system: a review

et al. 2014

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Abstract. The Arctic climate system includes numerous highly interactive small-scale physical processes in the atmosphere, sea ice, and ocean. During and since the International Polar Year 2007-2009, significant advances have been made in understanding these processes. Here, these recent advances are reviewed, synthesized, and discussed. In atmospheric physics, the primary advances have been in cloud physics, radiative transfer, mesoscale cyclones, coastal, and fjordic processes as well as in boundary layer processes and surface fluxes. In sea ice and its snow cover, advances have been made in understanding of the surface albedo and its relationships with snow properties, the internal structure of sea ice, the heat and salt transfer in ice, the formation of superimposed ice and snow ice, and the small-scale dynamics of sea ice. For the ocean, significant advances have been related to exchange processes at the ice-ocean interface, diapycnal mixing, double-diffusive convection, tidal currents and diurnal resonance. Despite this recent progress, some of these small-scale physical processes are still not sufficiently understood: these include wave-turbulence interactions in the atmosphere and ocean, the exchange of heat and salt at the ice-ocean interface, and the mechanical weakening of sea ice. Many other processes are reasonably well understood as stand-alone processes but the challenge is to understand their interactions with and impacts and feedbacks on other processes. Uncertainty in the parameterization of small-scale processes continues to be among the greatest challenges facing climate modelling, particularly in high latitudes. Further improvements in parameterization require new year-round field campaigns on the Arctic sea ice, closely combined with satellite remote sensing studies and numerical model experiments.

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“…A comprehensive study of the three-dimensional structure and underlying physics of the PL based on the dropsonde data from three flight missions, infrared National Oceanic and Atmospheric Administration (NOAA) satellite images, and products from the operational Norwegian High Resolution Limited Area Model (HIRLAM) (Undén et al, 2002) was presented by Føre et al (2011). In short, crosssections of dropsonde data showed that the horizontal gradients of potential temperature weakened as the PL matured, which suggested that baroclinic energy conversion took place.…”

Section: Introductionmentioning

confidence: 99%

“…However, it is not easy to understand either the separate roles of condensational heating (i.e. the air is heated from release of latent heat by condensation), surface energy fluxes, and baroclinic energy conversion or their interactions for the PL intensity by using only the dropsonde data and HIRLAM analyses presented in Føre et al (2011).…”

Section: Introductionmentioning

confidence: 99%

A polar low observed over the Norwegian Sea on 3–4 March 2008: high‐resolution numerical experiments

Føre

Nordeng

2012

Quart J Royal Meteoro Soc

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A polar low (PL) observed over the Norwegian Sea by the IPY-THORPEX research aircraft campaign during 3-4 March 2008 was studied by a series of fine-mesh (3 km) experiments using the state-of-the-art Weather Research and Forecasting (WRF) model. The full-physics experiment simulated the PL intensity, baroclinic nature, surface wind speed and track rather well compared to dropsonde observations and satellite images. Two types of sensitivity experiments were designed to analyse the physical properties of the PL. First, physical processes such as condensational heating and sensible and/or latent heat fluxes were switched off throughout the whole simulation. In the second type, these processes were turned off at later times, which minimized the modification of the polar low environment caused by the absence of one or all of them over a long time period, making it suitable to study the direct effect of the physical processes on the PL itself. These two types of sensitivity experiments suggested the following: low-level baroclinic energy conversion was of primary importance for the PL development, while other physical processes had a minor direct impact on the PL intensity. The surface latent heat fluxes, and to a lesser extent sensible heat fluxes, played an indirect role in the sense that they set up and supported the baroclinic environment vital for the PL development. Condensational heating, however, was essential to set up the initial baroclinic environment favourable for the PL intensification, while it had a modest indirect effect thereafter. The experiments indicated that in the late mature stage, after baroclinicity vanished, surface energy fluxes (sensible and/or latent heat) might have contributed to the PL energetics. How the variability in the simulated moist convection, the thermal structure of the PL core, and surface energy fluxes in each experiment affected the PL was difficult to answer.

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The full life cycle of a polar low over the Norwegian Sea observed by three research aircraft flights

Cited by 34 publications

References 33 publications

The role of horizontal resolution for polar low simulations

The role of horizontal resolution for polar low simulations

Advances in understanding and parameterization of small-scale physical processes in the marine Arctic climate system: a review

A polar low observed over the Norwegian Sea on 3–4 March 2008: high‐resolution numerical experiments

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