scholarly journals Temporal Characteristics of Heat Waves and Cold Spells and Their Links to Atmospheric Circulation in EURO-CORDEX RCMs

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Eva Plavcová ◽  
Jan Kyselý
Keyword(s):  
Atmospheric Circulation ◽  
Heat Waves ◽  
Dominant Role ◽  
Winter Season ◽  
Zonal Flow ◽  
Substantial Improvement ◽  
Temperature Extremes ◽  
Circulation Types ◽  
The Mean ◽  
Almost All

We study summer heat waves and winter cold spells and their links to atmospheric circulation in an ensemble of EURO-CORDEX RCMs in Central Europe. Results of 19 simulations were compared against observations over 1980–2005. Atmospheric circulation was represented by circulation types and supertypes derived from daily gridded mean sea level pressure. We examined observed and simulated characteristics of hot and cold days (defined using percentiles of temperature anomalies from the mean annual cycle) and heat waves and cold spells (periods of at least three hot/cold days in summer/winter). Although the ensemble of RCMs reproduces on average the frequency and the mean length of heat waves and cold spells relatively well, individual simulations suffer from biases. Most model runs have an enhanced tendency to group hot/cold days into sequences, with several simulations leading to extremely long heat waves or cold spells (the maximum length overestimated by up to 2-3 times). All simulations also produce an extreme winter season with (often considerably) higher number of cold days than in any observed winter. The RCMs reproduce in general the observed circulation significantly conducive to heat waves and cold spells. Zonal flow reduces the probability of temperature extremes in both seasons, while advection of warm/cold air from the south-easterly/north-easterly quadrant plays a dominant role in developing heat waves/cold spells. Because of these links, the simulation of temperature extremes in RCMs is strongly affected by biases in atmospheric circulation. For almost all simulations and all circulation supertypes, the persistence of supertypes is significantly overestimated (even if the frequency of a given supertype is underestimated), which may contribute to development of too-long heat waves/cold spells. We did not identify any substantial improvement in the EURO-CORDEX RCMs in comparison to previous ENSEMBLES RCMs, but the patterns of the biases are generally less conclusive as to general RCMs’ drawbacks.

scholarly journals Relationships of surface air temperature anomalies over Europe to persistence of atmospheric circulation patterns conducive to heat waves

2008 ◽  
Vol 14 ◽  
pp. 243-249 ◽  
Author(s):  
J. Kyselý ◽  
R. Huth
Keyword(s):  
Atmospheric Circulation ◽  
Air Temperature ◽  
Heat Waves ◽  
Temperature Extremes ◽  
Human Society ◽  
Positive Temperature ◽  
Temperature Anomalies ◽  
Circulation Types ◽  
Circulation Patterns ◽  
Air Temperature Anomalies

Abstract. Heat waves are among natural hazards with the most severe consequences for human society, including pronounced mortality impacts in mid-latitudes. Recent studies have hypothesized that the enhanced persistence of atmospheric circulation may affect surface climatic extremes, mainly the frequency and severity of heat waves. In this paper we examine relationships between the persistence of the Hess-Brezowsky circulation types conducive to summer heat waves and air temperature anomalies at stations over most of the European continent. We also evaluate differences between temperature anomalies during late and early stages of warm circulation types in all seasons. Results show that more persistent circulation patterns tend to enhance the severity of heat waves and support more pronounced temperature anomalies. Recent sharply rising trends in positive temperature extremes over Europe may be related to the greater persistence of the circulation types, and if similar changes towards enhanced persistence affect other mid-latitudinal regions, analogous consequences and implications for temperature extremes may be expected.

scholarly journals Relationship between Water Temperature of Polish Rivers and Large-Scale Atmospheric Circulation

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1690 ◽  
Author(s):  
Renata Graf ◽  
Dariusz Wrzesiński
Keyword(s):  
Water Temperature ◽  
Atmospheric Circulation ◽  
Large Scale ◽  
Statistical Significance ◽  
Winter Season ◽  
Circulation Type ◽  
River Waters ◽  
Positive And Negative Coefficients ◽  
Circulation Types ◽  
Temporal And Spatial Variability

The objective of the paper consisted in determining the effect of macroscale types of NAO, AO, EA, EAWR, SCAND, and AMO atmospheric circulation on changes in water temperature in Polish rivers. The study has made use of a broad body of hydrometeorological materials covering daily water temperature values for 96 water gauge stations located on 53 rivers and air temperature values for 43 meteorological stations. Percentage shares of positive and negative coefficients of correlation of annual, seasonal, and monthly circulation type indices with air and river water temperature were determined, demonstrating the character of teleconnection. Determinations were made of water temperature deviations in positive and negative phases of the analyzed indices from average values from the years 1971–2015, and their statistical significance ascertained. Research has shown that relations between the temperature of river waters in Poland and macroscale circulation types are not strong, however they are noticeable, sometimes even statistically significant, and both temporally and spatially diverse. NAO, AO, EA, and AMO indices are characterized by a generally positive correlation with temperature, whereas SCAND and EWAR indices are characterized by a negative correlation. Research showed a varying impact of types of atmospheric circulation, with their effectiveness increasing in the winter season. The strongest impact on temperature was observed for the positive and negative NAO and AO phases, when deviations of water temperature from average values are correspondingly higher (up to 1.0 °C) and lower (by a maximum of 1.5 °C), and also for the positive and negative SCAND phases, when water temperature are correspondingly lower (by a maximum of 0.8 °C) and higher (by 1.2 °C) than average values. The strongest impact on water temperature in summer, mainly in July, was observed for AMO. The results point to the complexity of processes determining the thermal regime of rivers and to the possibility of additional factors—both regional and local—exerting an influence on their temporal and spatial variability.

scholarly journals The occurrence of hot weather in the Lublin-Felin and Czesławice in relation to atmospheric circulation (1966–2010)

2016 ◽  
Vol 48 (1) ◽  
pp. 67-77
Author(s):  
Krzysztof Bartoszek ◽  
Alicja Węgrzyn
Keyword(s):  
Atmospheric Circulation ◽  
Heat Waves ◽  
Thermal Conditions ◽  
Well Being ◽  
Health Resort ◽  
Probability Of Occurrence ◽  
Circulation Types ◽  
Hot Days ◽  
Hot Weather

Abstract The occurrence of hot weather in the Lublin-Felin and Czesławice in relation to atmospheric circulation (1966−2010). The paper describes the occurrence of hot (tmax 25.1−30.0°C) and very hot days (tmax >30°C) in Lublin-Felin and Czesławice in the years 1966−2010. The analysis covers the long-term variability of such days, and duration of heat waves. Their circulation conditions were also determined, with indication of circulation types during which the probability of occurrence of hot and very hot days was the highest. In the study area, hot days occurred from April to September, and very hot days from May to August, with the highest frequency in July in both cases. In the period from 1991 to 2010, a considerably higher number of cases of very hot days were recorded than in the 1970s and 1980s. Moreover, they occurred in increasingly long sequences, contributing to more frequent occurrence of unfavourable thermal and humid conditions during the growing season of plants. The highest probability of occurrence of hot and very hot days was determined for circulation types with airflow from the southern sector, and the lowest from the northern sector. Should the upward trend in the frequency of very hot days continue, the risk of the effect of such unfavourable thermal conditions on the health and well-being of tourists and patients of the health resort in Nałęczów will also increase

Persistence and frequency of drought-relevant circulation types during temperature extremes in southern Central Europe

2020 ◽  
Author(s):  
Selina Thanheiser ◽  
Markus Homann ◽  
Andreas Philipp ◽  
Christoph Beck ◽  
Jucundus Jacobeit
Keyword(s):  
Atmospheric Circulation ◽  
Central Europe ◽  
Circulation Type ◽  
Efficiency Coefficient ◽  
Cold Waves ◽  
Temperature Anomalies ◽  
Circulation Types ◽  
Southern Central ◽  
The Mean ◽  
The Relationship

<p>The German weather service reports a new record mean June temperature for Germany and intensive heat waves during 2018 and 2019. Between January 2018 and June 2019, three new monthly top extremes were recorded (April 2018, May 2018 and June 2019).</p><p>In this study the relationships between the persistence and frequency of atmospheric circulation patterns related to drought and surface air temperature anomalies are investigated. The study area is in southern Central Europe, including parts of Germany and Switzerland as well as Austria and Czech Republic.</p><p>Large-scale atmospheric circulation types (relevant to drought) have been derived by using the COST733 classification software. Atmospheric variables from gridded daily JRA55 reanalysis data (Japanese Meteorological Agency 2018) and gridded precipitation data for the study area (6x6km, based on timeseries of 1756 weather stations from Zentralanstalt für Meteorologie und Geodynamik 2018) were used for the classification. All input variables were specifically weighted in the classification process. Daily maximum temperature data from ECA&D (2019) for different stations within the study area are used to evaluate the relationship between a circulation type and heat (cold) waves.</p><p>The drought-relevant circulation types are determined according to relative frequencies of circulation type days under a particular percentile of precipitation: If at least 20 percent of the circulation type days are below the 20th percentile of precipitation, the circulation type is defined as drought relevant.</p><p>For the derived drought-relevant circulation types, the mean seasonal frequencies [in %] (April-September, October-March) and the mean persistence [in days] (1961-2017) are calculated. To evaluate the relationship between a circulation type and heat (cold) waves, an efficiency coefficient is calculated. The efficiency coefficient is defined as ratio between the frequency of the circulation type in heat (cold) waves and its mean seasonal frequency.</p><p>For the study area, those circulation types relevant to drought with a high proportion of seasonal temperature anomalies could be identified. The circulation type with a dominant Azores high with ridges of high-pressure towards Central/Eastern Europe has the highest proportion of positive temperature anomalies in summer.</p>

scholarly journals Influence of springtime atmospheric circulation types on the distribution of air pollutants in the Arctic

2021 ◽  
Author(s):  
Manu Anna Thomas ◽  
Abhay Devasthale ◽  
Tiina Nygård
Keyword(s):  
Atmospheric Circulation ◽  
The Arctic ◽  
Transport Models ◽  
Self Organizing Maps ◽  
Atmospheric Circulation Patterns ◽  
Circulation Types ◽  
Circulation Patterns ◽  
European Arctic ◽  
Pollutant Distribution ◽  
Almost All

Abstract. The transport and distribution of short-lived climate forcers in the Arctic is influenced by the prevailing atmospheric circulation patterns. Understanding the coupling between pollutant distribution and dominant atmospheric circulation types is therefore important, not least to understand the processes governing the local processing of pollutants in the Arctic, but also to test the fidelity of chemistry transport models to simulate the transport from the southerly latitudes. Here, we use a combination of satellite based and reanalysis datasets spanning over 12 years (2007–2018) and investigate the concentrations of NO2, O3, CO and aerosols and their co-variability during 20 different atmospheric circulation types in the spring season (March, April and May) over the Arctic. We carried out a Self-Organizing Maps analysis of MSLP to derive these circulation types. Although almost all pollutants investigated here show statistically significant sensitivity to the circulation types, NO2 exhibits the strongest sensitivity among them. The circulation types with low-pressure systems located over the northeast Atlantic show a clear enhancement of NO2 and AOD in the European Arctic. The O3 concentrations are, however, decreased. The free tropospheric CO is increased over the Arctic during such events. The circulation types with atmospheric blocking over Greenland and northern Scandinavia show the opposite signal in which the NO2 concentrations are decreased and AODs are smaller than the climatological values. The O3 concentrations are, however, increased and the free tropospheric CO decreased during such events. The study provides the most comprehensive assessment so far of the sensitivity of springtime pollutant distribution to the atmospheric circulation types in the Arctic and also provides an observational basis for the evaluation of chemistry transport models.

scholarly journals Changes in the Atmospheric Circulation Conditions and Regional Climatic Characteristics in Two Remote Regions Since the Mid-20th Century

Atmosphere ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 11 ◽  
Author(s):  
Maria G. Lebedeva ◽  
Anthony R. Lupo ◽  
Yury G. Chendev ◽  
Olga V. Krymskaya ◽  
Aleksandr B. Solovyev
Keyword(s):  
Flow Regime ◽  
Atmospheric Circulation ◽  
Classification Scheme ◽  
Zonal Flow ◽  
Positive Temperature ◽  
Vegetation Growth ◽  
Circulation Types ◽  
Temperature And Precipitation ◽  
Precipitation Regimes ◽  
Central Usa

A meridional Northern Hemisphere (NH) circulation epoch, which began in 1957, is marked by changes in the temperature and precipitation regimes over southwest Russia and central USA depending on the occurrence of NH atmospheric circulation regimes. A classification scheme proposed in 1968, and studied later put forth 13 NH circulation types, fitting more broadly into four groups, two of which are more zonal type flows and two of which are more meridional flows. Using the results of a previous study that showed four distinct sub-periods during the 1957–2017 epoch, the temperature and precipitation regimes of both regions were studied across all seasons in order to characterize modern day climate variability and their suitability for vegetation growth. Then the Hydrologic Coefficient, which combined the temperature and precipitation variables, was briefly studied. The most optimal conditions for vegetation growth, positive temperature and precipitation anomalies, were noted during the period 1970–1980 for southwest Russia, which was dominated by an increasingly more zonal flow regime in the Belgorod region and NH in general. For the central USA, the HTC showed more ideal conditions for agriculture in recent years due to favorable precipitation occurrence. In southwest Russia, variable precipitation regimes were noted during the meridional flow periods, and with the increase in temperature (since 1998), these can adversely affect the hydrothermal characteristics of the growing season. Finally, a comparison of the 13 NH circulation types with several teleconnection indexes demonstrated the robustness of the NH flow regime classification scheme used here.

scholarly journals Influence of springtime atmospheric circulation types on the distribution of air pollutants in the Arctic

2021 ◽  
Vol 21 (21) ◽  
pp. 16593-16608
Author(s):  
Manu Anna Thomas ◽  
Abhay Devasthale ◽  
Tiina Nygård
Keyword(s):  
Atmospheric Circulation ◽  
The Arctic ◽  
Self Organizing Map ◽  
Transport Models ◽  
Sea Level Pressure ◽  
Atmospheric Circulation Patterns ◽  
Circulation Types ◽  
Pollutant Distribution ◽  
Almost All ◽  
Map Analysis

Abstract. The transport and distribution of short-lived climate forcers in the Arctic are influenced by the prevailing atmospheric circulation patterns. Understanding the coupling between pollutant distribution and dominant atmospheric circulation types is therefore important, not least to understand the processes governing the local processing of pollutants in the Arctic, but also to test the fidelity of chemistry transport models to simulate the transport from the southerly latitudes. Here, we use a combination of satellite-based and reanalysis datasets spanning over 12 years (2007–2018) and investigate the concentrations of NO2, O3, CO and aerosols and their co-variability during eight different atmospheric circulation types in the spring season (March, April and May) over the Arctic. We carried out a self-organizing map analysis of mean sea level pressure to derive these circulation types. Although almost all pollutants investigated here show statistically significant sensitivity to the circulation types, NO2 exhibits the strongest sensitivity among them. The circulation types with low-pressure systems located over the northeast Atlantic show a clear enhancement of NO2 and aerosol optical depths (AODs) in the European Arctic. The O3 concentrations are, however, decreased. The free tropospheric CO is increased over the Arctic during such events. The circulation types with atmospheric blocking over Greenland and northern Scandinavia show the opposite signal in which the NO2 concentrations are decreased and AODs are smaller than the climatological values. The O3 concentrations are, however, increased, and the free tropospheric CO is decreased during such events. The study provides the most comprehensive assessment so far of the sensitivity of springtime pollutant distribution to the atmospheric circulation types in the Arctic and also provides an observational basis for the evaluation of chemistry transport models.

scholarly journals ATMOSPHERIC DROUGHT IN THE POLISH TATRAS AND THEIRFORELAND IN THE YEARS 1951–2017

2021 ◽  
Vol 20 (1) ◽  
pp. 55-67
Author(s):  
Marta Cebulska ◽  
Keyword(s):  
Atmospheric Circulation ◽  
Standardized Precipitation Index ◽  
Atmospheric Precipitation ◽  
Kendall Test ◽  
Drought Severity ◽  
Monthly Precipitation ◽  
Significance Level ◽  
Circulation Types ◽  
Almost All ◽  
The Impact

Aim of the study. The aim of this study is to assess the variability of the lowest monthly totals of precipitation, and to evaluate the impact of atmospheric circulation on the occurrence of months with a deficit of precipitation. Material and methods. Material: The monthly totals of atmospheric precipitation for the years 1951–2017 from 19 meteorological stations located in the Polish Tatra Mountains and in their foreland. and the calendar of atmospheric circulation types for southern Poland, which was developed by Niedźwiedź (1981; 2018). Methods: Standardized Precipitation Index (SPI), the Mann-Kendall test Results and conclusions. No statistically significant trend at a significance level of 0.05 was noted in the course of the lowest monthly precipitation totals at any of the meteorological stations. In the 67-year period, all the measuring stations saw a total of 499 (3.3%) dry months with varying drought severity. The largest number of extremely dry months occurred in August and April, respectively. In the case of months when the lowest totals of precipitation occurred in the same month at all or almost all of the meteorological stations, three types of anticyclonic circulation dominated, i.e. eastern, south-eastern, southern, and the anticyclonic wedge.

SEM Cold Stage Techniques for the Observation of Vegetative and Floral Apices of Oat (Avena sativa L.) Plants

1977 ◽  
Vol 35 ◽  
pp. 590-591
Author(s):  
B. K. Kirchoff ◽  
L.F. Allard ◽  
W.C. Bigelow
Keyword(s):  
Critical Point ◽  
Avena Sativa ◽  
Substantial Improvement ◽  
Fresh Tissue ◽  
Cold Stage ◽  
Critical Point Drying ◽  
Almost All ◽  
Cell Collapse ◽  
Conductive Paint ◽  
Carbon Based

In attempting to use the SEM to investigate the transition from the vegetative to the floral state in oat (Avena sativa L.) it was discovered that the procedures of fixation and critical point drying (CPD), and fresh tissue examination of the specimens gave unsatisfactory results. In most cases, by using these techniques, cells of the tissue were collapsed or otherwise visibly distorted. Figure 1 shows the results of fixation with 4.5% formaldehyde-gluteraldehyde followed by CPD. Almost all cellular detail has been obscured by the resulting shrinkage distortions. The larger cracks seen on the left of the picture may be due to dissection damage, rather than CPD. The results of observation of fresh tissue are seen in Fig. 2. Although there is a substantial improvement over CPD, some cell collapse still occurs.Due to these difficulties, it was decided to experiment with cold stage techniques. The specimens to be observed were dissected out and attached to the sample stub using a carbon based conductive paint in acetone.

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