Isentropic Analysis of Polar Cold Airmass Streams in the Northern Hemispheric Winter

Abstract An analysis method is proposed for polar cold airmass streams from generation to disappearance. It designates a threshold potential temperature θT at around the turning point of the extratropical direct (ETD) meridional circulation from downward to equatorward in the mass-weighted isentropic zonal mean (MIM) and clarifies the geographical distributions of the cold air mass, the negative heat content (NHC), their horizontal fluxes, and their diabatic change rates on the basis of conservation relations of the air mass and thermodynamic energy. In the Northern Hemispheric winter, the polar cold air mass below θT = 280 K has two main streams: the East Asian stream and the North American stream. The former grows over the northern part of the Eurasian continent, flows eastward, turns down southeastward toward East Asia via Siberia, and disappears over the western North Pacific Ocean. The latter grows over the Arctic Ocean, flows toward the eastern coast of North America via Hudson Bay, and disappears over the western North Atlantic Ocean. In their exit regions, wave–mean flow interactions are considered to transfer the angular momentum from the cold airstreams to the upward Eliassen–Palm flux and convert the available potential energy to wave energy.

Download Full-text

Charge and discharge of polar cold air mass in northern hemispheric winter

Geophysical Research Letters ◽

10.1002/2015gl065626 ◽

2015 ◽

Vol 42 (17) ◽

pp. 7187-7193 ◽

Cited By ~ 16

Author(s):

Yuki Kanno ◽

Muhammad Rais Abdillah ◽

Toshiki Iwasaki

Keyword(s):

Air Mass ◽

Cold Air ◽

Northern Hemispheric

Download Full-text

A Match-based approach to the estimation of polar stratospheric ozone loss using Aura Microwave Limb Sounder observations

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-9945-2015 ◽

2015 ◽

Vol 15 (17) ◽

pp. 9945-9963 ◽

Cited By ~ 21

Author(s):

N. J. Livesey ◽

M. L. Santee ◽

G. L. Manney

Keyword(s):

Stratospheric Ozone ◽

Potential Temperature ◽

Polar Vortex ◽

Rate Of Change ◽

The Arctic ◽

Air Mass ◽

Ozone Loss ◽

Chemical Destruction ◽

Induced Changes ◽

The Impact

Abstract. The well-established "Match" approach to quantifying chemical destruction of ozone in the polar lower stratosphere is applied to ozone observations from the Microwave Limb Sounder (MLS) on NASA's Aura spacecraft. Quantification of ozone loss requires distinguishing transport- and chemically induced changes in ozone abundance. This is accomplished in the Match approach by examining cases where trajectories indicate that the same air mass has been observed on multiple occasions. The method was pioneered using ozonesonde observations, for which hundreds of matched ozone observations per winter are typically available. The dense coverage of the MLS measurements, particularly at polar latitudes, allows matches to be made to thousands of observations each day. This study is enabled by recently developed MLS Lagrangian trajectory diagnostic (LTD) support products. Sensitivity studies indicate that the largest influence on the ozone loss estimates are the value of potential vorticity (PV) used to define the edge of the polar vortex (within which matched observations must lie) and the degree to which the PV of an air mass is allowed to vary between matched observations. Applying Match calculations to MLS observations of nitrous oxide, a long-lived tracer whose expected rate of change is negligible on the weekly to monthly timescales considered here, enables quantification of the impact of transport errors on the Match-based ozone loss estimates. Our loss estimates are generally in agreement with previous estimates for selected Arctic winters, though indicating smaller losses than many other studies. Arctic ozone losses are greatest during the 2010/11 winter, as seen in prior studies, with 2.0 ppmv (parts per million by volume) loss estimated at 450 K potential temperature (~ 18 km altitude). As expected, Antarctic winter ozone losses are consistently greater than those for the Arctic, with less interannual variability (e.g., ranging between 2.3 and 3.0 ppmv at 450 K). This study exemplifies the insights into atmospheric processes that can be obtained by applying the Match methodology to a densely sampled observation record such as that from Aura MLS.

Download Full-text

Two new species of Suberitida (Porifera, Heteroscleromorpha) from the Bering Sea

Zootaxa ◽

10.11646/zootaxa.4338.3.9 ◽

2017 ◽

Vol 4338 (3) ◽

pp. 546

Author(s):

HELMUT LEHNERT

Keyword(s):

New Species ◽

Bering Sea ◽

North Atlantic Ocean ◽

North Pacific Ocean ◽

First Record ◽

The Arctic ◽

Valid Species ◽

The North ◽

Two New Species ◽

The Bering Sea

Two new species, Plicatellopsis borealis and Spongosorites beringensis, from the Bering Sea are described; both belong to genera previously not reported from the area. The genus Plicatellopsis, Burton, 1932 (Porifera, Suberitida, Suberitidae) contains five valid species, all recorded from the southern hemisphere. The record of P. borealis n. sp. from the Bering Sea is consequently the first record of the genus from the northern hemisphere. The genus Spongosorites Topsent, 1896 (Porifera, Suberitida, Halichondriidae) contains 22 valid species but none reported from the North Pacific Ocean, Bering Sea or the Arctic Ocean. The geographically closest records are six species occurring in the North Atlantic Ocean. So the description of Spongosorites beringensis n.sp. is the first record of the genus in the region.

Download Full-text

Searching for the Elusive Cold-Type Occluded Front

Monthly Weather Review ◽

10.1175/mwr-d-14-00003.1 ◽

2014 ◽

Vol 142 (8) ◽

pp. 2565-2570 ◽

Cited By ~ 4

Author(s):

David M. Schultz ◽

Bogdan Antonescu ◽

Alessandro Chiariello

Keyword(s):

Temperature Difference ◽

Cross Sections ◽

Frontal Zone ◽

North Atlantic Ocean ◽

Air Mass ◽

Cold Air ◽

Weather Forecasts ◽

The North ◽

Medium Range ◽

Frontal Zones

Abstract According to the Norwegian cyclone model, whether a warm-type or cold-type occluded front forms depends upon which cold air mass is colder: the prewarm-frontal air mass or the postcold-frontal air mass. For example, a cold-type occlusion is said to occur when the occluded front slopes rearward with height because the prewarm-frontal air mass is warmer than the postcold-frontal air mass. This temperature difference and the resulting occluded-frontal structure in the Norwegian cyclone model is part of what is called the temperature rule. Paradoxically, no clear example of a rearward-sloping, cold-type occluded front has been found in the literature, even though the required temperature difference has been documented in several cases. This article presents the first documented, rearward-sloping, cold-type occluded front. This occluded front forms in a cyclone over the North Atlantic Ocean on 3–5 January 2003 and is documented in model output from the European Centre for Medium-Range Weather Forecasts. Cross sections through the evolving cyclone show the occluded front forms as the less statically stable warm-frontal zone ascends over the more stable cold-frontal zone. Such a stability difference between the cold- and warm-frontal zones is consistent with a previously published hypothesis that the less stable air is lifted by the more stable air to form occluded fronts, in disagreement with the temperature rule. Because warm-frontal zones and the cold air underneath tend to be more stable than cold-frontal zones and the postcold-frontal air, warm-type occluded fronts are much more common than cold-type occluded fronts, explaining why well-defined, rearward-sloping, cold-type occluded fronts are not common in the meteorological literature.

Download Full-text

Mechanisms of the time-varying sea surface height and heat content trends in the eastern Nordic Seas

10.5194/os-2019-109 ◽

2019 ◽

Cited By ~ 1

Author(s):

Sara Broomé ◽

Léon Chafik ◽

Johan Nilsson

Keyword(s):

North Atlantic ◽

Decadal Variability ◽

North Atlantic Ocean ◽

Heat Budget ◽

Heat Content ◽

Sea Surface Height ◽

Sea Surface ◽

The Arctic ◽

Nordic Seas ◽

Sea Surface Heights

Abstract. The Nordic Seas is the main ocean conveyor of heat between the North Atlantic Ocean and the Arctic Ocean. Although the decadal variability of the Subpolar North Atlantic has been given significant attention lately, especially regarding the cooling trend since mid-2000s, less is known about the potential connection downstream in the northern basins. Using sea surface heights from satellite altimetry over the past 25 years (1993–2017), we find significant variability on multiyear-to-decadal time scales in the Nordic Seas. In particular, the regional trends in sea surface height show signs of a slowdown since mid-2000s as compared to the rapid increase in the preceding decade since early 1990s. This change is most prominent in the Atlantic origin waters in the eastern Nordic Seas and is closely linked, as estimated from hydrography, to heat content. Furthermore, we formulate a simple heat budget for the eastern Nordic Seas to discuss the relative importance of local and remote sources of variability; advection of temperature anomalies in the Atlantic inflow is found to be the main mechanism. A conceptual model of ocean heat convergence, with only upstream temperature measurements at the inflow to the Nordic Seas as input, is able to reproduce key aspects of the decadal variability of the Nordic Seas' heat content. Based on these results, we argue that there is a strong connection with the upstream Subpolar North Atlantic. However, although the shift in trends in the mid-2000s is coincident in the Nordic Seas and the Subpolar North Atlantic, the eastern Nordic Seas has not seen a reversal of trends but instead maintain elevated sea surface heights and heat content in the recent decade considered here.

Download Full-text

Interannual Variability of the North American Cold Air Stream and Associated Synoptic Circulations

Journal of Climate ◽

10.1175/jcli-d-17-0104.1 ◽

2017 ◽

Vol 30 (23) ◽

pp. 9575-9590 ◽

Cited By ~ 8

Author(s):

Yuki Kanno ◽

John E. Walsh ◽

Toshiki Iwasaki

Keyword(s):

United States ◽

Interannual Variability ◽

Rocky Mountains ◽

Arctic Oscillation ◽

Potential Temperature ◽

The Arctic ◽

Boreal Winter ◽

Stratospheric Polar Vortex ◽

Cold Air ◽

The Arctic Oscillation

In boreal winter, the cold air mass (CAM) flux of air with a potential temperature below 280 K forms climatological mean CAM streams in East Asia and North America (NA). This study diagnoses the interannual variability of the NA stream by an analysis of the CAM flux across 60°N between Greenland and the Rocky Mountains. The first empirical orthogonal function (EOF) represents the variations in intensity of the NA stream. When the first principal component (PC1) is highly positive, the central part of the NA stream is intensified, with cold anomalies east of the Rocky Mountains. At the same time, a stratospheric polar vortex tends to split or displace toward NA. PC1 is highly correlated with the tropical Northern Hemisphere pattern, implying that this pattern is associated with the intensity of the NA stream. The second EOF shows a longitudinal shift of the NA stream toward Greenland or the Rocky Mountains. A highly negative PC2 results in a cold anomaly from western Canada to the Midwestern United States and anomalous heavy snowfall in the northeastern United States. PC2 is positively correlated with the Arctic Oscillation, which suggests that the longitudinal position of the NA stream varies with the Arctic Oscillation. These results illustrate how the intensity and location of cold air outbreaks vary with large-scale modes of atmospheric variability, with corresponding implications for the predictability of winter severity in NA.

Download Full-text

A Lagrangian Climatology of Wintertime Cold Air Outbreaks in the Irminger and Nordic Seas and Their Role in Shaping Air–Sea Heat Fluxes

Journal of Climate ◽

10.1175/jcli-d-16-0605.1 ◽

2017 ◽

Vol 30 (8) ◽

pp. 2717-2737 ◽

Cited By ~ 34

Author(s):

Lukas Papritz ◽

Thomas Spengler

Keyword(s):

Heat Fluxes ◽

The Arctic ◽

Eastern Coast ◽

Sensible Heat ◽

Transport Pathways ◽

Nordic Seas ◽

Cold Air ◽

Air Masses ◽

Irminger Sea ◽

Cold Air Outbreaks

Understanding the climatological characteristics of marine cold air outbreaks (CAOs) is of critical importance to constrain the processes determining the heat flux forcing of the high-latitude oceans. In this study, a comprehensive multidecadal climatology of wintertime CAO air masses is presented for the Irminger Sea and Nordic seas. To investigate the origin, transport pathways, and thermodynamic evolution of CAO air masses, a novel methodology based on kinematic trajectories is introduced. The major conclusions are as follows: (i) The most intense CAOs occur as a result of Arctic outflows following Greenland’s eastern coast from the Fram Strait southward and west of Novaya Zemlya. Weak CAOs also originate in flow across the SST gradient associated with the Arctic Front separating the Greenland and Iceland Seas from the Norwegian Sea. A substantial fraction of Irminger CAO air masses originate in the Canadian Arctic and overflow southern Greenland. (ii) CAOs account for 60%–80% of the wintertime oceanic heat loss associated with few intense CAOs west of Svalbard and in the Greenland, Iceland, and Barents Seas and frequent weak CAOs in the Norwegian and Irminger Seas. (iii) The amount of sensible heat extracted by CAO air masses is set by their intensity and their pathway over the underlying SST distribution, whereas the amount of latent heat is additionally capped by the SST. (iv) Among all CAO air masses, those in the Greenland and Iceland Seas extract the most sensible heat from the ocean and undergo the most intense diabatic warming. Irminger Sea CAO air masses experience only moderate diabatic warming but pick up more moisture than the other CAO air masses.

Download Full-text

Northern hemisphere cold air outbreaks are more likely to be severe during weak polar vortex conditions

Communications Earth & Environment ◽

10.1038/s43247-021-00215-6 ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Jinlong Huang ◽

Peter Hitchcock ◽

Amanda C. Maycock ◽

Christine M. McKenna ◽

Wenshou Tian

Keyword(s):

Northern Hemisphere ◽

Energy Use ◽

Climate Model ◽

Polar Vortex ◽

Anomalous Behavior ◽

The Arctic ◽

Stratospheric Polar Vortex ◽

Air Mass ◽

Cold Air ◽

Cold Air Outbreaks

AbstractSevere cold air outbreaks have significant impacts on human health, energy use, agriculture, and transportation. Anomalous behavior of the Arctic stratospheric polar vortex provides an important source of subseasonal-to-seasonal predictability of Northern Hemisphere cold air outbreaks. Here, through reanalysis data for the period 1958–2019 and climate model simulations for preindustrial conditions, we show that weak stratospheric polar vortex conditions increase the risk of severe cold air outbreaks in mid-latitude East Asia by 100%, in contrast to only 40% for moderate cold air outbreaks. Such a disproportionate increase is also found in Europe, with an elevated risk persisting more than three weeks. By analysing the stream of polar cold air mass, we show that the polar vortex affects severe cold air outbreaks by modifying the inter-hemispheric transport of cold air mass. Using a novel method to assess Granger causality, we show that the polar vortex provides predictive information regarding severe cold air outbreaks over multiple regions in the Northern Hemisphere, which may help with mitigating their impact.

Download Full-text

The unusually long cold spell and the snowstorm Filomena over Spain in January 2021

10.5194/ems2021-98 ◽

2021 ◽

Author(s):

Philipp Zschenderlein ◽

Heini Wernli

Keyword(s):

Land Surface ◽

Potential Temperature ◽

Low Pressure ◽

Cold Spell ◽

Pressure System ◽

Optimal Position ◽

Cold Temperatures ◽

Air Mass ◽

Cold Air ◽

Low Pressure System

In January 2021, large parts of Spain were affected by an unusually long cold spell and exceptional snowfall associated with the winter storm Filomena. According to the Spanish weather service AEMET, snow heights of nearly 50 cm were registered in and around Madrid. During the days after Filomena, record-breaking low temperatures were measured at many stations.Already during the days before the arrival of storm Filomena, anomalously cold temperatures at 850 hPa and night frosts at the surface prevailed over large parts of Spain. During these days in early January, the air flow towards Spain was predominantly northeasterly and advected cold air masses from Central Europe, as revealed by backward trajectories that were initialised near the surface over Spain. The land surface progressively cooled down during the days prior to the heavy snowfall, which then prevented the snow from melting when reaching the surface. Therefore, this cold spell preconditioning seems to be very important for the extreme consequences of the snowfall event.The storm Filomena affected Spain between 8 and 10 January. It developed from a precursor low-pressure system between the Azores and Madeira. The precursor low-pressure system itself developed on 2 January 2021 between the northeastern US and Nova Scotia, rapidly intensified along a potential vorticity (PV) streamer and propagated southeastwards. Between 4 and 6 January, the cyclone, now located near the Azores, was associated with a PV cut-off and eventually decayed into multiple centres. Out of this decaying low-pressure system, Filomena developed and reached Spain on 8 January.The most intense snowfall occurred on 9 January and affected large parts of Spain, except for southwestern Spain, where temperatures were too high and all precipitation fell as rain. Filomena was associated with an intense air mass boundary, with dry and cold air in the north and warm and humid air in the south. Equivalent potential temperature differences at 850 hPa across Spain exceeded 20 K. Along the warm frontal part of this air mass boundary, strong ascending airstreams, intensified by the dynamics of Filomena, led to cloud formation. Due to the unusually cold lowermost troposphere, snow was not melting before reaching the land surface, and the surface snow layer could therefore easily grow.Overall, the combination of the already cold temperatures near the surface, the optimal position of the air mass boundary, and the dynamical forcing for ascent at this intense baroclinic zone associated with Filomena were essential ingredients for this extreme snow fall event to occur.

Download Full-text

Mechanisms of decadal changes in sea surface height and heat content in the eastern Nordic Seas

Ocean Science ◽

10.5194/os-16-715-2020 ◽

2020 ◽

Vol 16 (3) ◽

pp. 715-728

Author(s):

Sara Broomé ◽

Léon Chafik ◽

Johan Nilsson

Keyword(s):

North Atlantic ◽

Decadal Variability ◽

North Atlantic Ocean ◽

Heat Budget ◽

Heat Content ◽

Sea Surface Height ◽

Sea Surface ◽

The Arctic ◽

Nordic Seas ◽

Sea Surface Heights

Abstract. The Nordic Seas constitute the main ocean conveyor of heat between the North Atlantic Ocean and the Arctic Ocean. Although the decadal variability in the subpolar North Atlantic has been given significant attention lately, especially regarding the cooling trend since the mid-2000s, less is known about the potential connection downstream in the northern basins. Using sea surface heights from satellite altimetry over the past 25 years (1993–2017), we find significant variability on multiyear to decadal timescales in the Nordic Seas. In particular, the regional trends in sea surface height show signs of a weakening since the mid-2000s, as compared to the rapid increase in the preceding decade since the early 1990s. This change is most prominent in the Atlantic origin waters in the eastern Nordic Seas and is closely linked, as estimated from hydrography, to heat content. Furthermore, we formulate a simple heat budget for the eastern Nordic Seas to discuss the relative importance of local and remote sources of variability; advection of temperature anomalies in the Atlantic inflow is found to be the main mechanism. A conceptual model of ocean heat convergence, with only upstream temperature measurements at the inflow to the Nordic Seas as input, is able to reproduce key aspects of the decadal variability in the heat content of the Nordic Seas. Based on these results, we argue that there is a strong connection with the upstream subpolar North Atlantic. However, although the shift in trends in the mid-2000s is coincident in the Nordic Seas and the subpolar North Atlantic, the eastern Nordic Seas have not seen a reversal of trends but instead maintain elevated sea surface heights and heat content in the recent decade considered here.

Download Full-text