Marine cold-air outbreaks in the future: an assessment of IPCC AR4 model results for the Northern Hemisphere

Kolstad, Erik W.; Bracegirdle, Thomas J.

doi:10.1007/s00382-007-0331-0

Cited by 113 publications

(137 citation statements)

References 61 publications

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“…On the basis of reanalysis data, Kolstad et al (2009) concluded that seasonal and interannual variability of CAOs is mostly governed by the variability of the 700 hPa air temperature, T700, rather than by the sea surface temperature. Using a rough measure of CAO occurrence based, for example, on T700, Kolstad and Bracegirdle (2008) concluded that climate models broadly capture the observed climatology of CAOs, but differences from observations occur in areas where models have excessive sea ice cover. As energy fluxes are very large in CAOs and extensive ocean regions are affected, small differences in the CAO occurrence and properties may have a large effect on the regional ocean-atmosphere heat flux.…”

Section: Atmosmentioning

confidence: 99%

“…Due to their high impact, predictions of any changes in frequency or location of occurrence are important. A couple of recent studies address this: Kolstad and Bracegirdle (2008) use marine cold air outbreaks as a proxy for polar low activity; while Zahn and von Storch (2010) use dynamical downscaling to simulate polar mesoscale cyclones. In both studies a migration northwards is found, following the retreating sea ice pack, and consequently there is a decrease in the frequency of polar lows through the 21st century.…”

Section: Mesoscale Cyclonesmentioning

confidence: 99%

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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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Section: Atmosmentioning

confidence: 99%

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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“…As the SSHF can be sensitive to the T variability during fall, it is particularly interesting to explore its relation- ship with negative SATs. In model simulations, the occurrence of cold air advection (CAA) events and increased T is known to release copious amounts of ocean heat flux and trigger the seasonal recovery of sea ice (Deser et al, 2010;Kolstad and Bracegirdle, 2008). Models also project that future occurrences of CAA may spread further poleward along the retreating sea ice margin (Kolstad and Bracegirdle, 2008).…”

Section: Characteristics Of Sshf Over the Open Arcticmentioning

confidence: 99%

“…In model simulations, the occurrence of cold air advection (CAA) events and increased T is known to release copious amounts of ocean heat flux and trigger the seasonal recovery of sea ice (Deser et al, 2010;Kolstad and Bracegirdle, 2008). Models also project that future occurrences of CAA may spread further poleward along the retreating sea ice margin (Kolstad and Bracegirdle, 2008). In spite of recent observations and modeling efforts (Inoue and Hori, 2011;Klein et al, 2009), there are limited measurements of actual surface fluxes during such events.…”

Section: Characteristics Of Sshf Over the Open Arcticmentioning

confidence: 99%

The open-ocean sensible heat flux and its significance for Arctic boundary layer mixing during early fall

Ganeshan¹,

2016

Atmos. Chem. Phys.

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Abstract. The increasing ice-free area during late summer has transformed the Arctic to a climate system with more dynamic boundary layer (BL) clouds and seasonal sea ice growth. The open-ocean sensible heat flux, a crucial mechanism of excessive ocean heat loss to the atmosphere during the fall freeze season, is speculated to play an important role in the recently observed cloud cover increase and BL instability. However, lack of observations and understanding of the resilience of the proposed mechanisms, especially in relation to meteorological and interannual variability, has left a poorly constrained BL parameterization scheme in Arctic climate models. In this study, we use multiyear Japanese cruise-ship observations from R/V Mirai over the open Arctic Ocean to characterize the surface sensible heat flux (SSHF) during early fall and investigate its contribution to BL turbulence. It is found that mixing by SSHF is favored during episodes of high surface wind speed and is also influenced by the prevailing cloud regime. The deepest BLs and maximum ocean-atmosphere temperature difference are observed during cold air advection (associated with the stratocumulus regime), yet, contrary to previous speculation, the efficiency of sensible heat exchange is low. On the other hand, the SSHF contributes significantly to BL mixing during the uplift (low pressure) followed by the highly stable (stratus) regime. Overall, it can explain ∼ 10 % of the openocean BL height variability, whereas cloud-driven (moisture and radiative) mechanisms appear to be the other dominant source of convective turbulence. Nevertheless, there is strong interannual variability in the relationship between the SSHF and the BL height which can be intensified by the changing occurrence of Arctic climate patterns, such as positive surface wind speed anomalies and more frequent conditions of uplift. This study highlights the need for comprehensive BL observations like the R/V Mirai for better understanding and predicting the dynamic nature of the Arctic climate.

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“…In the Northern Hemisphere, the most favoured regions for polar low formation are over the northernmost extent of the warm ocean currents (Gulf Stream, Kuroshio) and in regions with frequent MCAOs, such as over the Labrador, Irminger, Norwegian and Barents Seas, as well as near Japan and over the Sea of Okhotsk (Kolstad, 2011). Recently, substantial changes in polar low frequency in a future warmer climate have been suggested (Kolstad and Bracegirdle, 2008;Zahn and von Storch, 2010), drawing attention to the importance of a better understanding of this intriguing phenomenon.…”

Section: Introductionmentioning

confidence: 99%

Orographic influence of east Greenland on a polar low over the Denmark Strait

Kristjánsson

Þorsteinsson

Kolstad

et al. 2011

Quart J Royal Meteoro Soc

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We present a numerical study of a polar low which hit western Iceland in January 2007, with heavy snowfall and mean wind speeds exceeding 20 m s −1 in several locations. The operational models at the time captured the polar low formation rather well, but there was a large spread in their predictions of the subsequent evolution and track of the polar low. The objective of this study is to investigate possible orographic forcing from Greenland as a trigger for the polar low development. In addition to an analysis of surface observations and satellite imagery, sensitivity studies using HIRLAM were carried out with various degradations of Greenland's orography, as well as with modifications to the sea-surface temperature (SST), surface roughness and the data assimilation scheme. Despite the presence of an upper-level trough and weak static stability in all the simulations, the polar low development was found to be very sensitive to the presence of the high mountains of eastern Greenland. Whereas the control run captured well the main features of the polar low, simulations with parts of east Greenland's orography removed gave a southward-displaced polar low which moved rapidly eastward, resulting in substantially underestimated nearsurface winds and snowfall amounts. Setting the orographic heights over all of Greenland to zero led to the complete disappearance of the polar low. On the other hand, artificially increasing the SST by 4 K in the Denmark Strait, reducing the orographic roughness or replacing the four-dimensional variational assimilation scheme (4D-Var) by 3D-Var had only a small effect on the polar low. We suggest that hitherto unreported interactions between the high mountains of east Greenland and polar low development over the Denmark Strait may be more important for polar low formation than katabatic flow from valleys in east Greenland that was highlighted in earlier studies.

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Marine cold-air outbreaks in the future: an assessment of IPCC AR4 model results for the Northern Hemisphere

Cited by 113 publications

References 61 publications

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

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

The open-ocean sensible heat flux and its significance for Arctic boundary layer mixing during early fall

Orographic influence of east Greenland on a polar low over the Denmark Strait

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