scholarly journals The Icelandic Low as a Predictor of the Gulf Stream North Wall Position

2016 ◽  
Vol 46 (3) ◽  
pp. 817-826 ◽  
Author(s):  
Alejandra Sanchez-Franks ◽  
Sultan Hameed ◽  
Robert E. Wilson
Keyword(s):  
Gulf Stream ◽  
Southern Oscillation ◽  
Time Lags ◽  
Grand Banks ◽  
The North ◽  
Cape Hatteras ◽  
Pressure Anomaly ◽  
Icelandic Low ◽  
North Wall ◽  
Wall Position

AbstractThe Gulf Stream’s north wall east of Cape Hatteras marks the abrupt change in velocity and water properties between the slope sea to the north and the Gulf Stream itself. An index of the north wall position constructed by Taylor and Stephens, called Gulf Stream north wall (GSNW), is analyzed in terms of interannual changes in the Icelandic low (IL) pressure anomaly and longitudinal displacement. Sea surface temperature (SST) composites suggest that when IL pressure is anomalously low, there are lower temperatures in the Labrador Sea and south of the Grand Banks. Two years later, warm SST anomalies are seen over the Northern Recirculation Gyre and a northward shift in the GSNW occurs. Similar changes in SSTs occur during winters in which the IL is anomalously west, resulting in a northward displacement of the GSNW 3 years later. Although time lags of 2 and 3 years between the IL and the GSNW are used in the calculations, it is shown that lags with respect to each atmospheric variable are statistically significant at the 5% level over a range of years. Utilizing the appropriate time lags between the GSNW index and the IL pressure and longitude, as well as the Southern Oscillation index, a regression prediction scheme is developed for forecasting the GSNW with a lead time of 1 year. This scheme, which uses only prior information, was used to forecast the GSNW from 1994 to 2015. The correlation between the observed and forecasted values for 1994–2014 was 0.60, significant at the 1% level. The predicted value for 2015 indicates a small northward shift of the GSNW from its 2014 position.

scholarly journals Long-term variability of dust events in Iceland (1949–2011)

2014 ◽  
Vol 14 (24) ◽  
pp. 13411-13422 ◽  
Author(s):  
P. Dagsson-Waldhauserova ◽  
O. Arnalds ◽  
H. Olafsson
Keyword(s):  
Particulate Matter ◽  
Volcanic Eruptions ◽  
Dust Storms ◽  
The Arctic ◽  
Atmospheric Dust ◽  
The World ◽  
Icelandic Low ◽  
Dust Events ◽  
The 1960S

Abstract. The long-term frequency of atmospheric dust observations was investigated for the southern part of Iceland and interpreted together with earlier results obtained from northeastern (NE) Iceland (Dagsson-Waldhauserova et al., 2013). In total, over 34 dust days per year on average occurred in Iceland based on conventionally used synoptic codes for dust observations. However, frequent volcanic eruptions, with the re-suspension of volcanic materials and dust haze, increased the number of dust events fourfold (135 dust days annually). The position of the Icelandic Low determined whether dust events occurred in the NE (16.4 dust days annually) or in the southern (S) part of Iceland (about 18 dust days annually). The decade with the most frequent dust days in S Iceland was the 1960s, but the 2000s in NE Iceland. A total of 32 severe dust storms (visibility < 500 m) were observed in Iceland with the highest frequency of events during the 2000s in S Iceland. The Arctic dust events (NE Iceland) were typically warm, occurring during summer/autumn (May–September) and during mild southwesterly winds, while the subarctic dust events (S Iceland) were mainly cold, occurring during winter/spring (March–May) and during strong northeasterly winds. About half of the dust events in S Iceland occurred in winter or at sub-zero temperatures. A good correlation was found between particulate matter (PM10) concentrations and visibility during dust observations at the stations Vík and Stórhöfði. This study shows that Iceland is among the dustiest areas of the world and that dust is emitted year-round.

scholarly journals QUASI-STATIONARY PLANETARY WAVES IN MID-LATITUDE STRATOSPHERE–MESOSPHERE IN WINTER 2011-2020

2021 ◽  
pp. 307-311
Author(s):  
Chenning Zhang ◽  
Oleksandr Evtushevsky ◽  
Gennadi Milinevsky
Keyword(s):  
Surface Pressure ◽  
Satellite Data ◽  
Geopotential Height ◽  
Stationary Wave ◽  
Planetary Waves ◽  
Stationary Waves ◽  
Aleutian Low ◽  
The North ◽  
Pressure Anomaly ◽  
Icelandic Low

The 10-year climatology (2011–2020) of quasi-stationary planetary waves in the mid-latitude stratosphere and mesosphere (40–50N, up to 90 km) has been analyzed. Longitude–altitude sections of geopotential height and ozone have been obtained using the Aura MLS satellite data. It is found that stationary wave 1 propagates into the mesosphere from the North American High and Icelandic Low, which are adjacent surface pressure anomalies in the structure of stationary wave 2. Unexpectedly, the strongest pressure anomaly in the Aleutian Low region does not contribute to the stationary wave 1 formation in the mesosphere. The vertical phase transformations of stationary waves in geopotential height and ozone show inconsistencies that should be studied separately.

Synoptic climatological analysis on the rather abrupt seasonal transition to mid-winter situation around Germany with intermittent appearance of extremely low temperature events.

2020 ◽  
Author(s):  
Chihiro Miyake ◽  
Kuranoshin Kato
Keyword(s):  
Low Temperature ◽  
Large Scale ◽  
Reanalysis Data ◽  
Intraseasonal Variation ◽  
Easterly Wind ◽  
Seasonal Transition ◽  
The North ◽  
Mean Temperature ◽  
Icelandic Low ◽  
Appearance Frequency

&lt;p&gt;&amp;#160;&amp;#160;To know the detailed seasonal cycle in various regions, confined only to the middle and higher latitudes, is the common basis for deeper understanding of the seasonal backgrounds of (1) extreme meteorological or climatological events and (2) cultural generation through the &amp;#8220;seasonal feeling&amp;#8221; leading to cultural understanding education. For example, our previous studies (e.g., Kato et al. 2017) pointed out that the &amp;#8220;seasonal feeling&amp;#8221; on the severe winter relating to the traditional event for driving the winter away (&amp;#8220;Fasnacht&amp;#8221;) around Germany might be due to the intermittent appearance of the extremely low temperature events, although the winter mean temperature there is lower only by about 3~5&amp;#8451; than in southern Japan. Hamaki et al.(2018) suggested the appearance of such events to be controlled greatly by the&amp;#160;intraseasonal behaviors of the Icelandic low. Furthermore, Kuwana et al. (EGU2018 and 2019) pointed out the asymmetric seasonal progression of the behaviors of the Icelandic low including its intraseasonal variation from the autumn to the next spring. However, it has not been clarified yet what kind of seasonal transition of the dominant large-scale daily fields was related to the increase in appearance frequency of such extremely low temperature events after mid-December. Thus the present study will further examine the detailed features on the above processes, mainly for the 2000/2001 winter based on the NCEP/NCAR reanalysis data.&lt;/p&gt;&lt;p&gt;&amp;#160; Appearance frequency of extremely low temperature events (e.g., below -5&amp;#8451;) rapidly increased around mid-December of 2000 with the large amplitude of its intraseasonal variation although the seasonal mean the Icelandic low appeared from mid-October. It is interesting that the daily mean temperature decreased gradually with shorter-period fluctuation until mid-December, even after the seasonal formation of the Icelandic low.&lt;/p&gt;&lt;p&gt;&amp;#160;&amp;#160;As for the seasonal mean fields from mid-December to the next March, the northeastern portion of the Icelandic low area extended more closely to the northwestern Europe and the baroclinicity was enhanced especially to the south of ~55&amp;#176;N. Composite analyses suggest that the extremely low temperature events after mid-December around Germany was related not only to the weakening and westward retreat of the Icelandic low but also to the cold air advection by the low-level easterly wind along the southeastern edge of the intraseasonal-scale surface high to the north of Germany.&lt;/p&gt;

Characteristics of North European winter lightning related to a high positive North Atlantic Oscillation index

2020 ◽  
Author(s):  
Ivana Kolmašová ◽  
Kateřina Rosická ◽  
Ondřej Santolík
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Large Scale ◽  
Winter Season ◽  
Winter Climate ◽  
The North ◽  
Nao Index ◽  
The North Atlantic ◽  
Icelandic Low ◽  
Azores High

&lt;p&gt;The variability of winter climate in the North Atlantic region is predominantly driven by a large scale alternation of atmospheric masses between the Icelandic Low and Azores High pressure systems called the North Atlantic Oscillation (NAO) and characterized by the NAO index. The calculation of the NAO index is based on the difference between sea-level pressure strengths of the Azores High and the Icelandic Low. Unusually high positive values of the NAO index were observed to manifest themselves by above-average precipitation and severe winter storms over British Isles and other parts of northwestern and northern Europe.&lt;/p&gt;&lt;p&gt;In the last two decades, the winter season 2014/2015 exhibited the highest positive monthly NAO indexes. During this winter, newspapers in the UK, Germany, Poland, and Scandinavia reported extremely strong storms which caused huge power outages, damages of buildings, and collapses of traffic which paralyzed the daily life. As winter thunderstorms are also characterized by a higher production of very energetic lightning, we use the World Wide Lightning Location Network (WWLLN) data and investigate properties of lightning which occurred in the north European region from October 2014 to March 2015.&amp;#160; The dataset consists of more than 90 thousand lightning detections. We focus on spatial and temporal distribution of lightning strokes, their energies and multiplicity.&lt;/p&gt;&lt;p&gt;We have found that the diurnal distribution of lightning was random from November till February, while the afternoon peak typical for summer storms was noticeable only in October and March. The median energy of lightning strokes observed in October, November and March reached only about 10-20% of the median energy of strokes detected in December, January and February. The most energetic strokes were concentrated above the ocean close to the western coastal areas and appeared exclusively at night and in the morning hours.&lt;/p&gt;

scholarly journals Dynamic Linkage between Cold Air Outbreaks and Intensity Variations of the Meridional Mass Circulation

2015 ◽  
Vol 72 (8) ◽  
pp. 3214-3232 ◽  
Author(s):  
Yueyue Yu ◽  
Rongcai Ren ◽  
Ming Cai
Keyword(s):  
Mass Transport ◽  
Western Europe ◽  
Peak Time ◽  
Cold Air ◽  
Continental Scale ◽  
Icelandic Low ◽  
Meridional Mass Circulation ◽  
Azores High ◽  
Mass Circulation ◽  
Cold Air Outbreaks

Abstract This study investigates the dynamical linkage between the meridional mass circulation and cold air outbreaks using the ERA-Interim data covering the period 1979–2011. It is found that the onset date of continental-scale cold air outbreaks coincides well with the peak time of stronger meridional mass circulation events, when the net mass transport across 60°N in the warm or cold air branch exceeds ~88 × 109 kg s−1. During weaker mass circulation events when the net mass transport across 60°N is below ~71.6 × 109 kg s−1, most areas of the midlatitudes are generally in mild conditions except the northern part of western Europe. Composite patterns of circulation anomalies during stronger mass circulation events greatly resemble that of the winter mean, with the two main routes of anomalous cold air outbreaks being along the climatological routes of polar cold air: namely, via East Asia and North America. The Siberian high shifts westward during stronger mass circulation events, opening up a third route of cold air outbreaks through eastern Europe, where lies the poleward warm air route in the winter-mean condition. The strengthening of the Icelandic low and Azores high during stronger mass circulation events acts to close off the climatological-mean cold air route via western Europe; this is responsible for the comparatively normal temperature there. The composite pattern for weaker mass circulation events is generally reversed, where the weakening of the Icelandic low and Azores high, corresponding to the negative phase of the North Atlantic Oscillation (NAO), leads to the reopening and strengthening of the equatorward cold air route through western Europe, which is responsible for the cold anomalies there.

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