scholarly journals Characteristics of extratropical cyclones and precursors to windstorms in Northern Europe

2021 ◽  
Author(s):  
Terhi K. Laurila ◽  
Hilppa Gregow ◽  
Joona Cornér ◽  
Victoria A. Sinclair
Keyword(s):  
Potential Temperature ◽  
Storm Track ◽  
Warm Season ◽  
Cold Season ◽  
Northern Europe ◽  
Annual Number ◽  
Extratropical Cyclones ◽  
Maximum Wind ◽  
The North ◽  
Wind Gusts

Abstract. Extratropical cyclones play a major role in the atmospheric circulation, weather variability and can cause damage to society. Extratropical cyclones in Northern Europe, which is located at the end of the North Atlantic storm track, have been less studied than extratropical cyclones elsewhere. Our study investigates extratropical cyclones and windstorms in Northern Europe (which in this study covers Norway, Sweden, Finland, Estonia and parts of the Baltic, Norwegian and Barents Seas) by analysing their characteristics, spatial and temporal evolution and precursors. We examine cold and warm seasons separately to determine seasonal differences. We track all extratropical cyclones in Northern Europe, create cyclone composites and use an ensemble sensitivity method to analyse the precursors. The ensemble sensitivity analysis is a novel method in cyclone studies where linear regression is used to statistically identify what variables possibly influence the subsequent evolution of extratropical cyclones. We investigate windstorm precursors for both the minimum mean sea level pressure (MSLP) and for the maximum 10-m wind gusts. The annual number of extratropical cyclones and windstorms have a large inter-annual variability and no significant linear trends during 1980–2019. Windstorms originate and occur over the Barents and Norwegian Seas whereas weaker extratropical cyclones originate and occur over land areas in Northern Europe. During the windstorm evolution, the maximum wind gusts move from the warm sector to behind the cold front following the strongest pressure gradient. Windstorms in both seasons are located on the poleward side of the jet stream. The maximum wind gusts occur nearly at the same time than the minimum MSLP occurs. The cold season windstorms have higher sensitivities and thus are potentially better predictable than warm season windstorms, and the minimum MSLP has higher sensitivities than the maximum wind gusts. Of the four examined precursors, both the minimum MSLP and the maximum wind gusts are the most sensitive to the 850-hPa potential temperature anomaly i.e. the temperature gradient. Hence, this parameter is likely important when predicting windstorms in Northern Europe.

scholarly journals Characteristics of extratropical cyclones and precursors to windstorms in northern Europe

2021 ◽  
Vol 2 (4) ◽  
pp. 1111-1130
Author(s):  
Terhi K. Laurila ◽  
Hilppa Gregow ◽  
Joona Cornér ◽  
Victoria A. Sinclair
Keyword(s):  
Potential Temperature ◽  
Storm Track ◽  
Warm Season ◽  
Cold Season ◽  
Northern Europe ◽  
Annual Number ◽  
Extratropical Cyclones ◽  
Maximum Wind ◽  
The North ◽  
Wind Gusts

Abstract. Extratropical cyclones play a major role in the atmospheric circulation and weather variability and can cause widespread damage and destruction. Extratropical cyclones in northern Europe, which is located at the end of the North Atlantic storm track, have been less studied than extratropical cyclones elsewhere. Our study investigates extratropical cyclones and windstorms in northern Europe (which in this study covers Norway; Sweden; Finland; Estonia; and parts of the Baltic, Norwegian, and Barents seas) by analysing their characteristics, spatial and temporal evolution, and precursors. We examine cold and warm seasons separately to determine seasonal differences. We track all extratropical cyclones in northern Europe, create cyclone composites, and use an ensemble sensitivity method to analyse the precursors. The ensemble sensitivity analysis is a novel method in cyclone studies where linear regression is used to statistically identify what variables possibly influence the subsequent evolution of extratropical cyclones. We investigate windstorm precursors for both the minimum mean sea level pressure (MSLP) and for the maximum 10 m wind gusts. The annual number of extratropical cyclones and windstorms has a large inter-annual variability and no significant linear trends during 1980–2019. Windstorms originate and occur over the Barents and Norwegian seas, whereas weaker extratropical cyclones originate and occur over land areas in northern Europe. During the windstorm evolution, the maximum wind gusts move from the warm sector to behind the cold front following the strongest pressure gradient. Windstorms in both seasons are located on the poleward side of the jet stream. The maximum wind gusts occur nearly at the same time as the minimum MSLP occurs. The cold-season windstorms have higher sensitivities and thus are potentially better predictable than warm-season windstorms, and the minimum MSLP has higher sensitivities than the maximum wind gusts. Of the four examined precursors, both the minimum MSLP and the maximum wind gusts are the most sensitive to the 850 hPa potential temperature anomaly, i.e. the temperature gradient. Hence, this parameter is likely important when predicting windstorms in northern Europe.

Sources and transport pathways of precipitating waters in cold-season deep North Atlantic cyclones

2021 ◽  
Author(s):  
Lukas Papritz ◽  
Franziska Aemisegger ◽  
Heini Wernli
Keyword(s):  
North Atlantic ◽  
Gulf Stream ◽  
Water Cycle ◽  
Storm Track ◽  
Cold Season ◽  
Surface Fluxes ◽  
Extratropical Cyclones ◽  
Transport Pathways ◽  
The North ◽  
Cyclone Tracking

AbstractExtratropical cyclones are responsible for a large share of precipitation at mid-latitudes and they profoundly impact the characteristics of the water cycle. In this study, we use the ERA5 reanalysis and a cyclone tracking scheme combined with a Lagrangian diagnostic to identify the sources of moisture precipitating close to the center of 676 deep North Atlantic cyclones in winters 1979 to 2018. Moisture uptakes occur pre-dominantly in originally cold and dry air heated over the North Atlantic, in particular, over the warm waters of the Gulf Stream, whereas more remote sources from land or the subtropics are less important. Analysing the dynamical environment of moisture uptakes, we find that moisture precipitating during the cyclone intensification phase originates in the pre-cyclone environment in the cold sectors of preceding cyclones and the cyclone-anticyclone interaction zone. These moisture sources are linked to the cyclone’s ascent regions via the so-called feeder airstream, a north-easterly cyclone-relative flow that arises due to the cyclone propagation exceeding the advection by the low-level background flow. During the decay phase more and more of the moisture originates in the cyclone’s own cold sector. Consequently, the residence time of precipitating waters in cyclones is short (median of ≈ 2 days) and transport distances are typically less than the distance travelled by the cyclone itself. These findings emphasize the importance of pre-conditioning by surface fluxes in the pre-cyclone environment for the formation of precipitation in cyclones, and suggest an important role for the hand-over of moisture from one cyclone to the next within a storm track.

scholarly journals Comparing Frontal Structures of Extratropical Cyclones in the Northwestern Pacific and Northwestern Atlantic Storm Tracks

2021 ◽  
Author(s):  
Eigo Tochimoto ◽  
Hiroshi Niino
Keyword(s):  
Conceptual Models ◽  
Potential Temperature ◽  
Storm Track ◽  
Horizontal Gradient ◽  
Northwestern Pacific ◽  
Extratropical Cyclones ◽  
Reanalysis Dataset ◽  
Cold Fronts ◽  
The North ◽  
The Difference

AbstractThe frontal structures of extratropical cyclones developing in the Northwestern Pacific storm track are relatively poorly understood compared with those in Europe and the Atlantic Ocean, for which representative conceptual models have been developed. In this paper, the structures of cyclones and their associated fronts in the Northwestern Pacific (NP), as well as in the Okhotsk Sea and Sea of Japan (OJ), are examined at their developing and mature stages using Japanese 55-year reanalysis dataset. Furthermore, the frontal structures in the NP are compared with those in the Northwestern Atlantic (NA). At the time of maximum deepening rate, cyclones in the NP are accompanied by strong warm and cold fronts, whereas cyclones in the OJ are more frequently accompanied by cold fronts than by warm fronts and tend to have stronger cold fronts than warm fronts. The weaker warm fronts than cold fronts to the east and northeast of cyclones in the OJ is likely due to the cyclones developing to the north and away from the region where the horizontal gradient of environmental potential temperature is strong. A comparison between mature cyclones in the NP and NA shows that the warm fronts in the NA tend to extend northeastward, whereas those in the NP extend more southeastward. These differences in warm fronts between NP and NA are suggested to be due to the difference in the horizontal structures of the warm currents between NP and NA.

scholarly journals Diet composition and feeding habits of the eyespot skate, Atlantoraja cyclophora (Elasmobranchii: Arhynchobatidae), off Uruguay and northern Argentina

2016 ◽  
Vol 14 (3) ◽  
Author(s):  
Santiago A. Barbini ◽  
Luis O. Lucifora
Keyword(s):  
Body Size ◽  
Diet Composition ◽  
Prey Size ◽  
Prey Availability ◽  
Feeding Habits ◽  
Warm Season ◽  
Cold Season ◽  
The North ◽  
Multiple Hypothesis ◽  
Modelling Approach

ABSTRACT The eyespot skate, Atlantoraja cyclophora, is an endemic species from the southwestern Atlantic, occurring from Rio de Janeiro, Brazil, to northern Patagonia, Argentina. The feeding habits of this species, from off Uruguay and north Argentina, were evaluated using a multiple hypothesis modelling approach. In general, the diet was composed mainly of decapod crustaceans, followed by teleost fishes. Molluscs, mysidaceans, amphipods, isopods, lancelets and elasmobranchs were consumed in lower proportion. The consumption of shrimps drecreased with increasing body size of A. cyclophora. On the other hand, the consumption of teleosts increased with body size. Mature individuals preyed more heavily on crabs than immature individuals. Teleosts were consumed more in the south region (34º - 38ºS) and crabs in the north region (38º - 41ºS). Shrimps were eaten more in the warm season than in the cold season. Prey size increased with increasing body size of A. cyclophora , but large individuals also consumed small teleosts and crabs. Atlantoraja cyclophora has demersal-benthic feeding habits, shifts its diet with increasing body size and in response to seasonal and regional changes in prey availability and distribution.

scholarly journals Understanding Land-Atmosphere-Climate Coupling from the Canadian Prairie Dataset

2018 ◽  
Author(s):  
Alan K Betts ◽  
Raymond L Desjardins
Keyword(s):  
Snow Cover ◽  
Diurnal Cycle ◽  
Radiative Forcing ◽  
Potential Temperature ◽  
Warm Season ◽  
Growing Season ◽  
Cold Season ◽  
Maximum Temperature ◽  
Canadian Prairie ◽  
Cloud Forcing

Analysis of the hourly Canadian Prairie data for the past 60 years has transformed our quantitative understanding of land-atmosphere-cloud coupling. The key reason is that trained observers made hourly estimates of opaque cloud fraction that obscures the sun, moon or stars, following the same protocol for 60 years at all stations. These 24 daily estimates of opaque cloud data are of sufficient quality that they can be calibrated against Baseline Surface Radiation Network data to give the climatology of the daily short-wave, longwave and total cloud forcing (SWCF, LWCF and CF). This key radiative forcing has not been available previously for climate datasets. Net cloud radiative forcing reverses sign from negative in the warm season to positive in the cold season, when reflective snow reduces the negative SWCF below the positive LWCF. This in turn leads to a large climate discontinuity with snow cover, with a systematic cooling of 10°C or more with snow cover. In addition, snow cover transforms the coupling between cloud cover and the diurnal range of temperature. In the warm season, maximum temperature increases with decreasing cloud, while minimum temperature barely changes; while in the cold season with snow cover, maximum temperature decreases with decreasing cloud and minimum temperature decreases even more. In the warm season, the diurnal ranges of temperature, relative humidity, equivalent potential temperature and the pressure height of the lifting condensation level are all tightly coupled to opaque cloud cover. Given over 600 station-years of hourly data, we are able to extract, perhaps for the first time, the coupling between cloud forcing and the warm season imbalance of the diurnal cycle; which changes monotonically from a warming and drying under clear skies to a cooling and moistening under cloudy skies with precipitation. Because we have the daily cloud radiative forci, which is large, we are able to show that the memory of water storage anomalies, from precipitation and the snowpack, goes back many months. The spring climatology shows the memory of snowfall back through the entire winter, and the memory in summer goes back to the months of snowmelt. Lagged precipitation anomalies modify the thermodynamic coupling of the diurnal cycle to the cloud forcing, and shift the diurnal cycle of mixing ratio which has a double peak. The seasonal extraction of the surface total water storage is a large damping of the interannual variability of precipitation anomalies in the growing season. The large land-use change from summer fallow to intensive cropping, which peaked in the early 1990s, has led to a coupled climate response that has cooled and moistened the growing season, lowering cloud-base, increasing equivalent potential temperature, and increasing precipitation. We show a simplified energy balance of the Prairies during the growing season and its dependence on reflective cloud.

scholarly journals CHROMOSOME STUDIES IN WILD POPULATIONS OF DROSOPHILA MELANOGASTER. II. RELATIONSHIP OF INVERSION FREQUENCIES TO LATITUDE, SEASON, WING-LOADING AND FLIGHT ACTIVITY

Genetics ◽  
1980 ◽  
Vol 95 (1) ◽  
pp. 211-223
Author(s):  
Harrison D Stalker
Keyword(s):  
Drosophila Melanogaster ◽  
Warm Season ◽  
Cold Season ◽  
South Texas ◽  
Temperature Adaptation ◽  
Wing Loading ◽  
Ambient Temperatures ◽  
The North ◽  
Wing Load ◽  
Relationship Of

ABSTRACT In the midwestern and eastern U.S. populations of Drosophila melanogaster, the Standard gene arrangements show higher frequencies in the north than in the south. In a Missouri population, and to a lesser extent in a south Texas population, the frequencies of Standard chromosomes regularly rise during the cold season and drop during the warm season, thus paralleling the north-south frequency differences. In the Missouri population in 1976 and 1978, wild males were tested far their ability to fly to bait at different ambient temperatures. In both years, males flying in nature in the temperature range of 13° to 15° showed significantly higher frequencies of Standard chromosomes than did those flying in the 16° to 28° range. Wild males flying at 13° to 15° also have different tharax/wing proportions and significantly lower wingloading indices than do those flying at 16° to 28°. Moreover, wild flies homozygous Standard in 2R and/or 3R have significantly lower wing-loading indices than flies carrying inversions in these arms. Thus, wild flies with high frequencies of Standard chromosommes are karyotypically northern, are selectively favored during the cold season, have a relatively low wing-load and are most capable of flying at critically low ambient temperatures.—In summary, in Missouri, presence or absence of the common cosmopolitan inversions is an important factor in low temperature adaptation, and at least part of the adaptive mechanism involves control of thorax/wing proportions and thus control of wing-loading.

scholarly journals Understanding Land–Atmosphere–Climate Coupling from the Canadian Prairie Dataset

Environments ◽  
2018 ◽  
Vol 5 (12) ◽  
pp. 129 ◽  
Author(s):  
Alan Betts ◽  
Raymond Desjardins
Keyword(s):  
Snow Cover ◽  
Diurnal Cycle ◽  
Radiative Forcing ◽  
Potential Temperature ◽  
Warm Season ◽  
Growing Season ◽  
Cold Season ◽  
Maximum Temperature ◽  
Canadian Prairie ◽  
Cloud Forcing

Analysis of the hourly Canadian Prairie data for the past 60 years has transformed our quantitative understanding of land–atmosphere–cloud coupling. The key reason is that trained observers made hourly estimates of the opaque cloud fraction that obscures the sun, moon, or stars, following the same protocol for 60 years at all stations. These 24 daily estimates of opaque cloud data are of sufficient quality such that they can be calibrated against Baseline Surface Radiation Network data to yield the climatology of the daily short-wave, long-wave, and total cloud forcing (SWCF, LWCF and CF, respectively). This key radiative forcing has not been available previously for climate datasets. Net cloud radiative forcing changes sign from negative in the warm season, to positive in the cold season, when reflective snow reduces the negative SWCF below the positive LWCF. This in turn leads to a large climate discontinuity with snow cover, with a systematic cooling of 10 °C or more with snow cover. In addition, snow cover transforms the coupling between cloud cover and the diurnal range of temperature. In the warm season, maximum temperature increases with decreasing cloud, while minimum temperature barely changes; while in the cold season with snow cover, maximum temperature decreases with decreasing cloud, and minimum temperature decreases even more. In the warm season, the diurnal ranges of temperature, relative humidity, equivalent potential temperature, and the pressure height of the lifting condensation level are all tightly coupled to the opaque cloud cover. Given over 600 station-years of hourly data, we are able to extract, perhaps for the first time, the coupling between the cloud forcing and the warm season imbalance of the diurnal cycle, which changes monotonically from a warming and drying under clear skies to a cooling and moistening under cloudy skies with precipitation. Because we have the daily cloud radiative forcing, which is large, we are able to show that the memory of water storage anomalies, from precipitation and the snowpack, goes back many months. The spring climatology shows the memory of snowfall back through the entire winter, and the memory in summer, goes back to the months of snowmelt. Lagged precipitation anomalies modify the thermodynamic coupling of the diurnal cycle to the cloud forcing, and shift the diurnal cycle of the mixing ratio, which has a double peak. The seasonal extraction of the surface total water storage is a large damping of the interannual variability of precipitation anomalies in the growing season. The large land-use change from summer fallow to intensive cropping, which peaked in the early 1990s, has led to a coupled climate response that has cooled and moistened the growing season, lowering cloud-base, increasing equivalent potential temperature, and increasing precipitation. We show a simplified energy balance of the Prairies during the growing season, and its dependence on reflective cloud.

scholarly journals Forecast of Hourly Airport Visibility Based on Artificial Intelligence Methods

Atmosphere ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 75
Author(s):  
Jin Ding ◽  
Guoping Zhang ◽  
Shudong Wang ◽  
Bing Xue ◽  
Jing Yang ◽  
...  
Keyword(s):  
Artificial Intelligence ◽  
Prediction Models ◽  
Warm Season ◽  
Northwest China ◽  
Cold Season ◽  
Central China ◽  
The North ◽  
Hourly Data ◽  
Artificial Intelligence Algorithm ◽  
Good Visibility

Based on the hourly visibility data, visibility and its changes during 2010–2020 at monthly and annual time scales over 47 international airports in China are investigated, and nine artificial-intelligence-based hourly visibility prediction models are trained (hourly data in 2018–2019) and tested (hourly data in 2020) at these airports. The analyses show that the visibility of airports in eastern and central China is at a poor level all year round, and LXA (in Lhasa) has good visibility all year round. Airports in south and the northwest China have better visibility from May to October and poorer visibility from November to April. In all months, the increasing visibility mainly occurs in the central, northeast and coastal areas of China, while decreasing visibility mainly appears in the western and northern parts of China. In spring, summer and autumn, the changes difference between east and west is particularly obvious. This East–West distribution of trends is obviously different from the North–South distribution shown by the mean. For all airports, good visibility mainly occurs from 14:00–18:00 p.m. Beijing Time, while poor visibility mainly concentrates from 22:00 p.m. to 12:00 p.m. the next day, especially between 3:00–9:00 a.m. Our proposed artificial intelligence algorithm models can be reasonably used in airport visibility prediction. In particular, most algorithm models have the best results in the visibility prediction over HFE (in Hefei) and SJW (in Shijiazhuang). On the contrary, the worst forecast results appear at LXA and LHW (in Lanzhou) airports. The prediction results of airport visibility in the cold season (October–December) are better than those in the warm season (May–September). Among the algorithm models, the prediction performance of the RF-based model is the best.

scholarly journals Assessing the Efficacy of A Marine Reserve to Protect Sharks With Differential Habitat Use

2020 ◽  
Author(s):  
Cesar Peñaherrera-Palma ◽  
Alistair Hobday ◽  
Alex Hearn ◽  
Eduardo Espinoza ◽  
George Shillinger ◽  
...  
Keyword(s):  
Marine Reserve ◽  
Warm Season ◽  
Environmental Parameters ◽  
Marine Species ◽  
Cold Season ◽  
Utilization Distribution ◽  
The North ◽  
South Central ◽  
Central Regions ◽  
Hammerhead Sharks

Abstract Spatial management through the implementation of marine protected areas is one strategy to limit the extraction of sensitive marine species. Understanding the area used by marine life is thus a key step towards the evaluation of the management framework and efficacy of a protected area. To provide information of the protective coverage of the Galapagos Marine Reserve (GMR), we assessed the habitat utilization distribution (UD) of hammerhead and blacktip sharks in the GMR. Fifteen hammerhead sharks and 27 blacktip sharks were tagged with SPOT and SPLASH satellite tags in the north and south-central regions of the GMR between 2007 and 2012. Our results show nearly 90% of hammerhead shark’s UD was enclosed by the reserve boundary during the cold season (June-October), yet this decreased to only ~30% with the advent of the warm season (December-April). Conversely, blacktip sharks’ UD was 100% enclosed by the reserve boundaries in all seasons. Season and depth were the most important environmental parameters defining the UD of hammerhead sharks; whilst year and eddy kinetic energy were the most important parameters for blacktip sharks. These findings suggest the size of the GMR may be effective for blacktip sharks but seasonally effective for hammerhead sharks.

scholarly journals An anomalous atmospheric river linked to the late June 2021 western North America heatwave

2022 ◽  
Author(s):  
Ruping Mo ◽  
Hai Lin ◽  
Frédéric Vitart
Keyword(s):  
North America ◽  
Water Vapour ◽  
Warm Season ◽  
Lower Troposphere ◽  
Heavy Precipitation ◽  
Cold Season ◽  
Feedback Mechanism ◽  
Western North America ◽  
Water Vapour Flux ◽  
The North

Abstract Atmospheric rivers (ARs) are long and narrow bands of enhanced water vapour flux concentrated in the lower troposphere. Many studies have documented the important role of cold-season ARs in producing heavy precipitation and triggering extreme flooding in many parts of the world. However, relatively little research has been conducted on the warm-season ARs and their impacts on extreme heatwave development. Here we show an anomalous warm-season AR moving across the North Pacific and its interaction with the western North American heatwave in late June 2021. We call it an “oriental express’’ to highlight its capability to transport tropical moisture to the west coast of North America from sources in Southeast Asia. Its landfall over the Alaska Panhandle lasted for more than two days and resulted in significant spillover of moisture into western Canada. We provide evidence that the injected water vapour was trapped under the heat dome and may have formed a positive feedback mechanism to regulate the heatwave development in western North America.

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