scholarly journals African dust outbreaks over the western Mediterranean basin: 11 year characterization of atmospheric circulation patterns and dust source areas

2014 ◽  
Vol 14 (5) ◽  
pp. 5495-5533 ◽  
Author(s):  
P. Salvador ◽  
S. Alonso ◽  
J. Pey ◽  
B. Artíñano ◽  
J. J. de Bustos ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Mediterranean Basin ◽  
Circulation Pattern ◽  
Western Mediterranean ◽  
Atmospheric Circulation Patterns ◽  
African Dust ◽  
Western Mediterranean Basin ◽  
Circulation Patterns ◽  
Impact Index ◽  
The Impact

Abstract. The occurrence of African dust outbreaks over the western Mediterranean basin were identified on an 11 year period (2001–2011). PM10 daily data from nine regional background air quality monitoring sites across the study area were compiled and the net dust load transported during each event was estimated. Then, the main atmospheric circulation patterns causing the transport of African air masses, were characterized by mean of an objective classification methodology of atmospheric variables fields. Next, the potential source areas of mineral dust, associated to each circulation pattern were identified by trajectory statistical methods. Finally, an impact index was calculated to estimate the incidence of the African dust outbreaks produced during each circulation pattern, on the levels of dust load in PM10 concentrations recorded in the different regions. Our results indicate that the values of the impact index and the areas affected by African dust, strongly depended on the atmospheric circulation pattern. Four circulation types were obtained by the classification procedure. Two of them (CT-1 and CT-4) occurred predominantly during the warm season, bringing dust from areas of Algeria, Tunisia, Western Sahara, western Libya and Mauritania. African dust outbreaks produced during the CT-4 were the most frequent across the period of study, generating the highest impact index over southern, central and eastern regions of the Iberian Peninsula as well as over the Balearic Islands. Conversely, the events caused by the CT-1 encompassed the highest impact index over the western areas of the Iberian Peninsula. The two remaining circulation types (CT-2 and CT-3) were more frequently observed during the spring season. The prevailing flows generated by these two atmospheric circulation patterns, carried mineral dust from areas of Algeria, Tunisia and Western Sahara, giving rise to higher values of the impact index from eastern to western areas of the western Mediterranean basin.

scholarly journals African dust outbreaks over the western Mediterranean Basin: 11-year characterization of atmospheric circulation patterns and dust source areas

2014 ◽  
Vol 14 (13) ◽  
pp. 6759-6775 ◽  
Author(s):  
P. Salvador ◽  
S. Alonso-Pérez ◽  
J. Pey ◽  
B. Artíñano ◽  
J. J. de Bustos ◽  
...  
Keyword(s):  
Mediterranean Basin ◽  
Circulation Pattern ◽  
Circulation Type ◽  
Western Mediterranean ◽  
Western Sahara ◽  
Source Areas ◽  
Atmospheric Circulation Patterns ◽  
African Dust ◽  
Western Mediterranean Basin ◽  
Circulation Patterns

Abstract. The occurrence of African dust outbreaks over different areas of the western Mediterranean Basin were identified on an 11-year period (2001–2011). The main atmospheric circulation patterns causing the transport of African air masses were characterized by means of an objective classification methodology of atmospheric variable fields. Next, the potential source areas of mineral dust, associated to each circulation pattern were identified by trajectory statistical methods. Finally, an impact index was calculated to estimate the incidence of the African dust outbreaks produced during each circulation pattern, in the areas of study. Four circulation types were obtained (I–IV) and three main potential source areas of African dust were identified (Western Sahara and Morocco; Algeria; northeastern Algeria and Tunisia). The circulation pattern I (24% of the total number of episodic days) produced the transport of dust mainly in summer from Western Sahara, southern Morocco and Tunisia. The circulation pattern IV (33%) brings dust mainly from areas of northern and southern Algeria in summer and autumn, respectively. The circulation pattern II (31%) favored the transport of dust predominantly from northern Algeria, both in spring and summer. Finally, the circulation type III was the less frequently observed (12%). It occurred mainly in spring and with less intensity in winter, carrying dust from Western Sahara and southern Morocco. Our findings point out that the most intense episodes over the western Mediterranean Basin were produced in the summer period by the circulation type I (over the western side of the Iberian Peninsula) and the circulation type IV (over the central and eastern sides of the Iberian Peninsula and the Balearic Islands).

scholarly journals Impact of COVID-19 Lockdown and Atmospheric Circulation on the Air Quality in Wuhan During Early 2020

2021 ◽  
Vol 299 ◽  
pp. 02011
Author(s):  
Youyong Xie ◽  
Xiefei Zhi
Keyword(s):  
Air Quality ◽  
Atmospheric Circulation ◽  
Air Pollutants ◽  
General Circulation ◽  
Circulation Pattern ◽  
Atmospheric Circulation Patterns ◽  
Atmospheric General Circulation ◽  
Circulation Patterns ◽  
The Impact

Previous studies indicated that the air quality was improved in Wuhan during COVID-19 lockdown. However, the impact of atmospheric general circulation on the changes of air quality has not been taken into account. The present study aims to discuss the improvement of air quality in Wuhan and its possible reasons during COVID-19 lockdown. The results showed that all air pollutants except O3 decreased in Wuhan during early 2020. The occurrence days of A, C, W and NW types’ circulation pattern during early 2020 are more than those during the same period of 1979-2020. The occurrence days of SW type’s circulation pattern is slightly less than those during early 1979-2020. With more occurrence days of these dominant atmospheric circulation patterns, the number of polluted days could rise in Wuhan during early 2020. Nevertheless, this scenario didn’t occur. The COVID-19 lockdown did improve the air quality in Wuhan during early 2020.

scholarly journals Spring Extreme Precipitation Days in North China and Their Reliance on Atmospheric Circulation Patterns During 1979–2019

2022 ◽  
pp. 1-41
Keyword(s):  
Climate Variability ◽  
Atmospheric Circulation ◽  
Extreme Precipitation ◽  
Interannual Variation ◽  
North China ◽  
Circulation Pattern ◽  
Southerly Wind ◽  
Atmospheric Circulation Patterns ◽  
Rain Gauges ◽  
Circulation Patterns

Abstract The interannual variation of springtime extreme precipitation (SEP) days in North China (NC) and their reliance on atmospheric circulation patterns are studied by using the continuous daily record of 396 rain gauges and the fifth generation of the European Centre for Medium-Range Weather Forecasts atmospheric reanalysis during 1979–2019. The SEP days are defined as the days when at least 10% of rain gauges in NC record daily precipitation no less than 10.5 mm. Results show that the number of SEP days shows large interannual variability but no significant trend in the study period. Using the objective classification method of the obliquely rotated principal analysis in T-mode, we classify the atmospheric circulation into five different patterns based on the geopotential height at 700 hPa. Three circulation patterns all have fronts and are associated with strong southerly wind, leading to 88% of SEP days in NC. The strong southerly wind may provide moisture and dynamic forcing for the frontal precipitation. The interannual variation of SEP days is related with the number of the three above-mentioned dominant circulation patterns. Further analysis shows that the West Pacific pattern could be one of the possible climate variability modes related to SEP days. This study reveals that the daily circulation pattern may be the linkage between SEP days and climate variability modes in NC.

scholarly journals Decadal Variability in the Impact of Atmospheric Circulation Patterns on the Winter Climate of Northern Russia

2021 ◽  
Vol 34 (3) ◽  
pp. 1005-1021
Author(s):  
Gareth J. Marshall
Keyword(s):  
Atmospheric Circulation ◽  
Decadal Variability ◽  
The Arctic ◽  
Temporal Consistency ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Dominant Pattern ◽  
Circulation Patterns ◽  
Northern Russia ◽  
The Impact

AbstractThe Arctic continues to warm at a much faster rate than the global average. One process contributing to “Arctic amplification” involves changes in low-frequency macroscale atmospheric circulation patterns and their consequent influence on regional climate. Here, using ERA5 data, we examine decadal changes in the impact of seven such patterns on winter near-surface temperature (SAT) and precipitation (PPN) in northern Russia and calculate the temporal consistency of any statistically significant relationships. We demonstrate that the 40-yr climatology hides considerable decadal variability in the spatial extent of such circulation pattern–climate relationships across the region, with few areas where their temporal consistency exceeds 60%. This is primarily a response to the pronounced decadal expansion/contraction and/or mobility of the circulation patterns’ centers of action. The North Atlantic Oscillation (NAO) is the dominant pattern (having the highest temporal consistency) affecting SAT west of the Urals. Farther east, the Scandinavian (SCA), Polar/Eurasian (POL), and West Pacific patterns are successively the dominant pattern influencing SAT across the West Siberian Plains, Central Siberian Plateau, and mountains of Far East Siberia, respectively. From west to east, the SCA, POL, and Pacific–North American patterns exert the most consistent decadal influence on PPN. The only temporally invariant significant decadal relationships occur between the NAO and SAT and the SCA and PPN in small areas of the North European Plain.

scholarly journals Characterization of dynamic and thermodynamic features of African dust outbreaks over the western Mediterranean basin: trend analysis for the 1948-2020 period

2021 ◽  
Author(s):  
Pedro Salvador ◽  
Jorge Pey ◽  
Noemí Pérez ◽  
Xavier Querol ◽  
Begoña Artíñano
Keyword(s):  
Time Evolution ◽  
Mediterranean Basin ◽  
Potential Temperature ◽  
Western Mediterranean ◽  
Layer Potential ◽  
Mean Values ◽  
African Dust ◽  
Circulation Types ◽  
Western Mediterranean Basin ◽  
Synoptic Conditions

<p>All African dust outbreaks (ADO) that increased the regional-background levels of PM at the SE, SW, E, Central, NW, N and NE regions of the Iberian Peninsula and the Balearic Islands have been identified from 2001 to 2020 using a well-known procedure (https://www.miteco.gob.es/images/es/metodologiaparaepisodiosnaturales-revabril2013_tcm30-186522.pdf). However, the meteorological tools (air mass back-trajectories, satellite imagery and numerical models for prediction of dust levels) and data bases (time series of PM levels registered at air quality monitoring stations) needed to perform the identification procedure are scarce before the year 2000. For this reason the occurrence of ADO in the western Mediterranean basin during the former decades has not been well addressed so far.</p><p>In this study we have used the NCEP/NCAR global reanalysis dataset fields of meteorological parameters to characterize the main distinctive synoptic dynamic and thermodynamic features that were associated to the development of ADO and analyze their time evolution in the 1948-2020 period.</p><p>First, the main synoptic circulation types that favored the occurrence of the ADO identified in 2001-2020 were obtained. With this aim, a circulation classification methodology was applied for classifying the daily fields of geopotential height at the 850 hPa level at 12 UTC into prevalent atmospheric circulation types for SW Europe and NW Africa.</p><p>Next, the daily mean values of the 1000-500 hPa layer geopotential thickness (GT), the mean 925-700 layer potential temperature (TPOT) and the anomalies of temperature at 850 hPa (TANOM) were computed over all the regions of study. High values of these thermodynamic variables are associated with the presence of warm, stable and dry air masses. In fact, significantly higher values of GT, TPOT and TANOM were obtained in all regions during days under ADO circulation types than during other days in 2001-2020.</p><p>Finally, we analyzed the time evolution of all the days under ADO circulation types and their associated daily mean values of GT, TPOT and TANOM over the regions of study using the Theil-Sen method from 1948 to 2020.</p><p>Our results show that the monthly number of days under ADO circulation types display an upward trend of 0.06 monthly days per year at the 99.9% confidence level. Statistically significant upward trends for the monthly mean values of GT, TPOT and TANOM were also obtained over all the regions during days under prevailing ADO circulation types in summer, spring and winter.</p><p>In summary, the frequency of the dynamic and thermodynamic synoptic conditions favouring the development of ADO over the western Mediterranean basin has increased over the last 70 years. These results are in line with the exacerbation of warm conditions registered in southern Europe during the last decades.</p><p>Acknowledgements:</p><p>This study was funded by research project POSAHPI (Agencia Estatal de Investigación, PID2019-108101RB-I00).</p>

Multiplatform analysis of a large anticyclonic eddy in the Algero-Provencal basin in 2019

2020 ◽  
Author(s):  
Aida Alvera-Azcárate ◽  
Alexander Barth ◽  
Charles Troupin ◽  
Jean-Marie Beckers ◽  
Hayley Evers-King ◽  
...  
Keyword(s):  
Mediterranean Basin ◽  
Cold Water ◽  
Remote Sensing Data ◽  
Western Mediterranean ◽  
Anticyclonic Eddy ◽  
Model Data ◽  
Multiple Sources ◽  
In Situ Data ◽  
Western Mediterranean Basin ◽  
The Impact

<p>A large anticyclonic eddy formed in April 2019 in the Algero-Provencal basin between Mallorca and Sardinia, and lasted until November 2019. While mesoscale activity is usually high in this part of the Mediterranean basin, the formation of such large (about 150 km in diameter) and long-lived eddies is not common. The eddy formed from a filament originated in the Algerian coast and was visible in multiple sources of satellite data, including sea surface temperature and ocean colour from Sentinel-3, until summer. Because of the warming of the surface layer, during summer months the eddy remained as a subsurface structure, evidenced by the sea level anomaly derived from altimetry data. A surface signal developed again in November, and the eddy finally dissipated in December 2019. According to CMEMS model data, in its strongest period the eddy reached about 300 m in depth, and during its sub-surface period the center was located at about 100 m depth. While at the surface the temperature signal was very clear, model data suggest the salinity anomaly was stronger than temperature, especially at depth. Such large and long-lived eddies have an impact in the basin currents, specifically in the transport of cold water from the northern to the southern part of the western Mediterranean basin, influencing the ecosystem there. The impact of the presence of this eddy, its long duration and the additional mesoscale and submesoscale activity that originated in its surroundings are investigated using a combination of remote sensing data, in situ data and model data.</p>

scholarly journals Relationship between winter orographic precipitation with synoptic and large-scale atmospheric circulation: The case of mount Olympus, Greece

2018 ◽  
Vol 52 (1) ◽  
pp. 45 ◽  
Author(s):  
Michael Nikolaos Styllas ◽  
Dimitrios Kaskaoutis
Keyword(s):  
Atmospheric Circulation ◽  
Large Scale ◽  
Rainfall Variability ◽  
Circulation Pattern ◽  
Western Mediterranean ◽  
The Arctic ◽  
Central Mediterranean ◽  
Winter Rainfall ◽  
Atmospheric Circulation Patterns ◽  
The North

The relationship between the winter (DJFM) precipitation and the atmospheric circulation patterns is examined around Mount Olympus, Greece in order to assess the effects of orography and atmospheric dynamics over a small (less than 100 x 100 km) spatial domain. Winter accumulated rainfall datasets from 8 stations spread along the eastern (marine) and western (continental) sides of the Mount Olympus at elevations between 30 m and 1150 m are used during the period 1981 to 2000. Synoptic scale conditions of mean sea-level pressure and geopotential heights at 850 hPa and 500 hPa, were used to explain the multiyear rainfall variability. High pressure systems dominated over the central Mediterranean and most parts of central Europe during the late 1980’s and early 1990’s, are associated with minimum winter rainfall along both sides of Mount Olympus. The winter of 1996 was associated with peak in rainfall along the marine side of the mountain and was characterized by enhancement of upper level trough over the western Mediterranean and increased low tropospheric depressions over the southern Adriatic and the Ionian Seas. This atmospheric circulation pattern facilitated a southeasterly air flow that affected more (less) the marine (continental) sides of the mountain. In contrast, dominance of low pressure systems with cores over the Gulf of Genoa and the Central Mediterranean affect the study area mostly from west/southwest revealing higher correlations with the precipitation in the continental side of the mountain (r= -0.80; Elassona station) and considerably lower correlations with the marine side (r = -0.67; Katerini station). This highlights the orographic barrier of the Mount Olympus revealing large differences between the upward and leeward sides. Large scale atmospheric patterns like the North Atlantic Oscillation and the Arctic Oscillation seem to influence the winter rainfall in the lowlands along the continental side of the mountain.

scholarly journals Climatology of aerosol optical properties and black carbon mass absorption cross section at a remote high altitude site in the Western Mediterranean Basin

2014 ◽  
Vol 14 (3) ◽  
pp. 3777-3814 ◽  
Author(s):  
M. Pandolfi ◽  
A. Ripoll ◽  
X. Querol ◽  
A. Alastuey
Keyword(s):  
Black Carbon ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Mediterranean Basin ◽  
Western Mediterranean ◽  
Absorption Cross ◽  
African Dust ◽  
Mass Absorption ◽  
Western Mediterranean Basin ◽  
Carbon Mass

Abstract. Aerosol light scattering, backscattering and absorption were measured at Montsec (MSC; 42°3' N, 0°44' E, 1570 m a.s.l.), a remote high-altitude site in the Western Mediterranean Basin. Mean (± sd) scattering, hemispheric backscattering and absorption were 18.9 ± 20.8 Mm−1, 2.6 ± 2.8 Mm−1 and 1.5 ± 1.4 Mm−1, respectively at 635 nm during the period under study (June 2011–June 2013). Mean values of single scattering albedo (635 nm), scattering Ångström exponent (450–635 nm), backscatter-to-scatter ratio (635 nm), asymmetry parameter (635 nm) and black carbon mass absorption cross section (637 nm) were 0.92 ± 0.03, 1.56 ± 0.88, 0.16 ± 0.09, 0.53 ± 0.16 and 10.9 ± 3.5 m2 g−1 respectively. The scattering measurements performed at MSC locate this site in the medium/upper range of values reported for other mountaintop sites in Europe mainly due to the frequent African dust episodes and regional recirculation scenarios occurring mostly in spring/summer and causing the presence of polluted layers at the MSC altitude. Under these conditions no clear diurnal cycles were observed for the measured extensive aerosol optical properties (scattering, absorption and extinction). Conversely, the mean particle absorption at MSC was relatively lower compared with other EU remote stations thus leading to relatively higher single scattering albedo compared with most European data. A season-dependent decrease in the magnitude of aerosol extensive properties was observed when MSC was in the free troposphere with the highest free-troposphere vs. all-data difference observed in winter and the lowest in spring/summer. The slope of the scattering vs. absorption relationship (among the lowest reported for other mountain top sites worldwide) indicates that the MSC site is dominated by dust aerosols at high aerosol loading. Correspondingly, scattering Ångström exponent and asymmetry parameter respectively decreased and increased indicating the shift toward larger particles associated with African dust episodes. The black carbon mass absorption cross section showed a clear annual cycle with higher values in summer when the occurrence of African dust outbreaks and regional recirculation scenarios favour the presence of aged black carbon particles in polluted layers at the MSC altitudes. The optical measurements performed at the MSC remote site were compared with those simultaneously performed at a regional background station in the Western Mediterranean Basin.

scholarly journals The role of atmospheric circulation patterns in driving recent changes in indices of extreme seasonal precipitation across Arctic Fennoscandia

2020 ◽  
Vol 162 (2) ◽  
pp. 741-759
Author(s):  
Gareth J. Marshall ◽  
Kirsti Jylhä ◽  
Sonja Kivinen ◽  
Mikko Laapas ◽  
Anita Verpe Dyrrdal
Keyword(s):  
Atmospheric Circulation ◽  
Spatial Relationship ◽  
Circulation Pattern ◽  
Major Influence ◽  
East Atlantic ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Extreme Precipitation Events ◽  
Circulation Patterns ◽  
Daily Precipitation Data

Abstract Extreme precipitation events (EPEs) have a major impact across Arctic Fennoscandia (AF). Here we examine the spatial variability of seasonal 50-year trends in three EPEs across AF for 1968–2017, using daily precipitation data from 46 meteorological stations, and analyse how these are related to contemporaneous changes in the principal atmospheric circulation patterns that impact AF climate. Positive trends in seasonal wet-day precipitation (PRCPTOT) are widespread across AF in all seasons except autumn. Spring (autumn) has the most widespread negative (positive) trends in consecutive dry days (CDD). There is less seasonal dependence for trends in consecutive wet days (CWDs), but the majority of the stations show an increase. Clear seasonal differences in the circulation pattern that exerted most influence on these AF EPE trends exist. In spring, PRCPTOT and CDD are most affected by the Scandinavian pattern at more than half the stations while it also has a marked influence on CWD. The East Atlantic/Western Russia pattern generally has the greatest influence on the most station EPE trends in summer and autumn, yet has no effect during either spring or winter. In winter, the dominant circulation pattern across AF varies more between the different EPEs, with the North Atlantic Oscillation, Polar/Eurasia and East Atlantic patterns all exerting a major influence. There are distinct geographical distributions to the dominant pattern affecting particular EPEs in some seasons, especially winter, while in others there is no discernible spatial relationship.

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