scholarly journals On the relationship between Arctic ice clouds and polluted air masses over the north slope of Alaska in April 2008

2013 ◽  
Vol 13 (2) ◽  
pp. 4331-4389 ◽  
Author(s):  
C. Jouan ◽  
J. Pelon ◽  
E. Girard ◽  
G. Ancellet ◽  
J. P. Blanchet ◽  
...  
Keyword(s):  
Eastern China ◽  
Weather Conditions ◽  
Ice Crystals ◽  
Ice Clouds ◽  
Air Masses ◽  
Airborne Measurements ◽  
The North ◽  
Synoptic Conditions ◽  
North Slope Of Alaska ◽  
Order Of Magnitude

Abstract. Recently, two Types of Ice Clouds (TICs) properties have been characterized using ISDAC airborne measurements (Alaska, April 2008). TIC-2B were characterized by fewer (<10 L−1) and larger (>110 μm) ice crystals, a larger ice supersaturation (>15%) and a fewer ice nuclei (IN) concentration (<2 order of magnitude) when compared to TIC-1/2A. It has been hypothesized that emissions of SO2 may reduce the ice nucleating properties of IN through acidification, resulting to a smaller concentration of larger ice crystals and leading to precipitation (e.g. cloud regime TIC-2B) because of the reduced competition for the same available moisture. Here, the origin of air masses forming the ISDAC TIC-1/2A (1 April 2008) and TIC-2B (15 April 2008) is investigated using trajectory tools and satellite data. Results show that the synoptic conditions favor air masses transport from the three potentials SO2 emission areas to Alaska: eastern China and Siberia where anthropogenic and biomass burning emission respectively are produced and the volcanic region from the Kamchatka/Aleutians. Weather conditions allow the accumulation of pollutants from eastern China/Siberia over Alaska, most probably with the contribution of acid volcanic aerosol during the TIC-2B period. OMI observations reveal that SO2 concentrations in air masses forming the TIC-2B were larger than in air masses forming the TIC-1/2A. Airborne measurements show high acidity near the TIC-2B flight where humidity was low. These results strongly support the hypothesis that acidic coating on IN are at the origin of the formation of TIC-2B.

scholarly journals On the relationship between Arctic ice clouds and polluted air masses over the North Slope of Alaska in April 2008

2014 ◽  
Vol 14 (3) ◽  
pp. 1205-1224 ◽  
Author(s):  
C. Jouan ◽  
J. Pelon ◽  
E. Girard ◽  
G. Ancellet ◽  
J. P. Blanchet ◽  
...  
Keyword(s):  
Eastern China ◽  
Weather Conditions ◽  
Ice Crystals ◽  
Ice Clouds ◽  
Air Masses ◽  
Airborne Measurements ◽  
The North ◽  
Synoptic Conditions ◽  
North Slope Of Alaska ◽  
Arctic Ice

Abstract. Recently, two types of ice clouds (TICs) properties have been characterized using the Indirect and Semi-Direct Aerosol Campaign (ISDAC) airborne measurements (Alaska, April 2008). TIC-2B were characterized by fewer (< 10 L−1) and larger (> 110 μm) ice crystals, and a larger ice supersaturation (> 15%) compared to TIC-1/2A. It has been hypothesized that emissions of SO2 may reduce the ice nucleating properties of ice nuclei (IN) through acidification, resulting in a smaller concentration of larger ice crystals and leading to precipitation (e.g., cloud regime TIC-2B). Here, the origin of air masses forming the ISDAC TIC-1/2A (1 April 2008) and TIC-2B (15 April 2008) is investigated using trajectory tools and satellite data. Results show that the synoptic conditions favor air masses transport from three potential SO2 emission sources into Alaska: eastern China and Siberia where anthropogenic and biomass burning emissions, respectively, are produced, and the volcanic region of the Kamchatka/Aleutians. Weather conditions allow the accumulation of pollutants from eastern China and Siberia over Alaska, most probably with the contribution of acidic volcanic aerosol during the TIC-2B period. Observation Monitoring Instrument (OMI) satellite observations reveal that SO2 concentrations in air masses forming the TIC-2B were larger than in air masses forming the TIC-1/2A. Airborne measurements show high acidity near the TIC-2B flight where humidity was low. These results support the hypothesis that acidic coating on IN could be at the origin of the formation of TIC-2B.

scholarly journals Processes contributing to cloud dissipation and formation events on the North Slope of Alaska

2021 ◽  
Vol 21 (5) ◽  
pp. 4149-4167
Author(s):  
Joseph Sedlar ◽  
Adele Igel ◽  
Hagen Telg
Keyword(s):  
Cloud Formation ◽  
North Slope ◽  
Near Surface ◽  
Air Mass ◽  
Low Level ◽  
Clear Sky ◽  
The North ◽  
Synoptic Conditions ◽  
North Slope Of Alaska ◽  
Low Cloud

Abstract. Clear-sky periods across the high latitudes have profound impacts on the surface energy budget and lower atmospheric stratification; however an understanding of the atmospheric processes leading to low-level cloud dissipation and formation events is limited. A method to identify clear periods at Utqiaġvik (formerly Barrow), Alaska, during a 5-year period (2014–2018) is developed. A suite of remote sensing and in situ measurements from the high-latitude observatory are analyzed; we focus on comparing and contrasting atmospheric properties during low-level (below 2 km) cloud dissipation and formation events to understand the processes controlling clear-sky periods. Vertical profiles of lidar backscatter suggest that aerosol presence across the lower atmosphere is relatively invariant during the periods bookending clear conditions, which suggests that a sparsity of aerosol is not frequently a cause for cloud dissipation on the North Slope of Alaska. Further, meteorological analysis indicates two active processes ongoing that appear to support the formation of low clouds after a clear-sky period: namely, horizontal advection, which was dominant in winter and early spring, and quiescent air mass modification, which was dominant in the summer. During summer, the dominant mode of cloud formation is a low cloud or fog layer developing near the surface. This low cloud formation is driven largely by air mass modification under relatively quiescent synoptic conditions. Near-surface aerosol particles concentrations changed by a factor of 2 around summer formation events. Thermodynamic adjustment and increased aerosol presence under quiescent atmospheric conditions are hypothesized as important mechanisms for fog formation.

Ice Nucleating Particles in Southern Chile and their connection to clouds 

2021 ◽  
Author(s):  
Heike Wex ◽  
Xianda Gong ◽  
Boris Barja ◽  
Patric Seifert ◽  
Martin Radenz ◽  
...  
Keyword(s):  
Warm Season ◽  
Weather Conditions ◽  
Chem Phys ◽  
Cold Season ◽  
Southern Chile ◽  
Backscatter Coefficient ◽  
Air Masses ◽  
North West ◽  
The North ◽  
Almost All

&lt;p&gt;Concentrations of atmospheric ice nucleating particles (INP) were obtained from weekly filter samples which were collected from May 2019 until March 2020 in southern Chile. Sampling took place at an altitude of 620m above sea level, on top of Cerro Mirador, a mountain directly to the west of Punta Arenas (53&amp;#176;S, 71&amp;#176;W). Additional aerosol properties such as particle number size distributions were measured as well. In parallel, ground-based remote sensing measurements with lidar and cloud radar were made in Punta Arenas.&lt;/p&gt;&lt;p&gt;INP concentrations were obtained from washing atmospheric aerosol particles off from deployed polycarbonate filters and subsequent analysis of the samples on two different freezing arrays which were used and described by us earlier (e.g., in Gong et al., 2019 and Hartmann et al., 2020). INP concentrations could be obtained over a broad temperature range from above -5&amp;#176;C down to -25&amp;#176;C.&lt;/p&gt;&lt;p&gt;INP concentrations were clearly higher than data obtained for the Southern Ocean region as reported in McCluskey et al. (2018) and Welti et al. (2020). Indeed, they were comparable to concentrations measured at Cape Verde (Gong et al., 2020). INP concentrations obtained during the warm season were spreading over ~ 2 orders of magnitude at any temperature. Data obtained for the cold season almost all were at the upper end of the observed INP concentration range, with only one weekly sample featuring low concentrations.&lt;/p&gt;&lt;p&gt;Heating of the samples was also applied, and the heated samples had clearly lower INP concentrations across the examined temperatures, implying a biological fraction among the INP of ~ 80%. Therefore, local terrestrial sources may be the source of the observed INP.&lt;/p&gt;&lt;p&gt;The assumption of local terrestrial sources is strengthened by a case study. For that, two subsequent samples obtained during the cold season were examined in more detail. These were the one sample with low INP concentrations which was obtained during the cold season during the week from August 14 to August 22, and the subsequent sample collected from August 22 to August 29, which was amongst the highest samples. Backward trajectories together with an analysis of Lidar data showed that the low INP concentrations were obtained for a time during which air masses predominantly came in from the south with little contact to land and for calm weather conditions. Conditions were not as stable during the following week which featured air masses mostly coming in from the north-west. The aerosol backscatter coefficient at the height level of the in-situ measurements was obtained from lidar observations for both weeks and shows about 50 % lower aerosol load for the first week, when INP concentrations were low.&lt;/p&gt;&lt;p&gt;All of this hints to local terrestrial sources for the observed highly ice active biogenic INP.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Literature:&lt;/p&gt;&lt;p&gt;Gong et al. (2019), Atmos. Chem. Phys., 19, 10883-10900, doi:10.5194/acp-19-10883-2019.&lt;/p&gt;&lt;p&gt;Gong et al. (2020), Atmos. Chem. Phys., 20, 1451-1468, doi:10.5194/acp-20-1451-2020.&lt;/p&gt;&lt;p&gt;Hartmann et al. (2020), Geophys. Res. Lett., 47, doi:10.1029/2020GL087770.&lt;/p&gt;&lt;p&gt;McCluskey et al. (2018), Geophys. Res. Lett., 45, doi:10.1029/2018gl079981.&lt;/p&gt;&lt;p&gt;Welti et a. (2020), Atmos. Chem. Phys. 20, doi:10.5194/acp-2020-466.&lt;/p&gt;

Wildfires in the eastern Mediterranean as a result of lightning activity – a change in the conventional knowledge

2016 ◽  
Vol 25 (5) ◽  
pp. 592 ◽  
Author(s):  
Shlomit Paz ◽  
Moshe Inbar ◽  
Haim Kutiel ◽  
Dan Malkinson ◽  
Naama Tessler ◽  
...  
Keyword(s):  
Eastern Mediterranean ◽  
Weather Conditions ◽  
Lightning Activity ◽  
Convective Storm ◽  
Air Masses ◽  
System A ◽  
First Case ◽  
Synoptic Conditions ◽  
History Of ◽  
Possible Cause

No records exist in the scientific literature about lightning fires in the eastern Mediterranean (EM). Although thunderstorms are frequent in winter, if spontaneous fire is ignited, it will immediately be extinguished by rain. No thunderstorms occur in summer, and therefore no favourable weather conditions for natural ignitions exist. In October 2014, the synoptic conditions over the EM comprised a Red Sea Trough (RST) with an easterly axis (a less frequent version of this system). A convective storm, accompanied by thunderstorms with intense local rains developed rapidly. Simultaneously, six wildfires were reported from different locations in northern Israel (in the EM). Lightning activity documented by the Israel Electric Co. was at the same time and locations as the reported wildfires. To the best of our knowledge, this is the first case recorded in recent history of wildfires in the EM as a result of lightning. Moreover, in the literature, the RST is associated with fires only when its axis is in a western position, thus driving very hot and dry air masses. A different way of thinking is needed on the potential of lightning in autumn as a possible cause of fires under different situations of the RST.

Investigation of the photochemical activity in different MPC outflows during EMeRGe

2020 ◽  
Author(s):  
Midhun George ◽  
Maria Dolores Andrés Hernández ◽  
Yangzhuoran Liu ◽  
Vladyslav Nenakhov ◽  
John Philip Burrows ◽  
...  
Keyword(s):  
East Asia ◽  
Peroxy Radical ◽  
Photochemical Activity ◽  
Peroxy Radicals ◽  
Essential Information ◽  
Air Masses ◽  
Airborne Measurements ◽  
Mixing Ratios ◽  
Photolysis Rates ◽  
Order Of Magnitude

&lt;p&gt;Since peroxy radicals are closely involved in a number of tropospheric chemical processes like O&lt;sub&gt;3&lt;/sub&gt; budget, hydrocarbon oxidation and acid formation, the accurate measurement of these radicals can provide essential information to improve our understanding of processing and transformation of polluted outflows from megacities and Major Population Centres (MPCs).&lt;/p&gt;&lt;p&gt;Airborne measurements of the total sum of peroxy radicals, RO&lt;sub&gt;2&lt;/sub&gt;* &amp;#160;= HO&lt;sub&gt;2&lt;/sub&gt; + &amp;#8721; RO&lt;sub&gt;2&lt;/sub&gt;, where R is an organic group, were conducted in Europe in summer 2017 and in East Asia in spring 2018 within the EMeRGe (Effect of Megacities on the Transport and Transformation of Pollutants on the Regional to Global Scales) project by using the PeRCEAS instrument (Peroxy Radical Chemical Enhancement and Absorption Spectrometer), on board of the HALO research aircraft (www.halo.dlr.de).&lt;/p&gt;&lt;p&gt;Over the course of both measurement campaigns different MPC outflows were investigated including among others, London, Rome, Manila and Taipei. Polluted air masses of different origin and composition were probed. Overall the peroxy radical mixing ratios were of the same order of magnitude in the air masses probed in Europe and in East Asia. The variations in the photochemical activity were studied by taking into account simultaneous observations of radical precursors and photolysis rates, while applying known oxidation mechanisms. Radical precursors, photolysis rates and aerosol load were generally higher in Asia, which might indicate higher radical loss reactions on the aerosol surface than in Europe. Moreover this study shows a clear deviation in the photostationary state for MPC outflows close to the emission sources. Based on this information, this presentation will focus on the actual understanding of the photochemical processing in the probed air masses.&lt;/p&gt;

scholarly journals Source-receptor relationships for airborne measurements of CO<sub>2</sub>, CO and O<sub>3</sub> above Siberia: a cluster-based approach

2010 ◽  
Vol 10 (4) ◽  
pp. 1671-1687 ◽  
Author(s):  
J.-D. Paris ◽  
A. Stohl ◽  
P. Ciais ◽  
P. Nédélec ◽  
B. D. Belan ◽  
...  
Keyword(s):  
Large Scale ◽  
Dispersion Model ◽  
Eastern China ◽  
Lower Troposphere ◽  
Particle Dispersion ◽  
Model Calculations ◽  
Air Masses ◽  
Airborne Measurements ◽  
Mixing Ratios ◽  
Source Regions

Abstract. We analysed results of three intensive aircraft campaigns above Siberia (April and September 2006, August 2007) with a total of ~70 h of continuous CO2, CO and O3 measurements. The flight route consists of consecutive ascents and descents between Novosibirsk (55° N, 82° E) and Yakutsk (62° N, 129° E). We performed retroplume calculations with the Lagrangian particle dispersion model FLEXPART for many short segments along the flight tracks. To reduce the extremely rich information on source regions provided by the model calculation into a small number of distinct cases, we performed a statistical clustering – to our knowledge for the first time – into potential source regions of the footprint emission sensitivities obtained from the model calculations. This technique not only worked well to separate source region influences but also resulted in clearly distinct tracer concentrations for the various clusters obtained. High CO and O3 concentrations were found associated with agricultural fire plumes originating from Kazakhstan in September 2006. A statistical analysis indicates that summer uptake of CO2 is largely explained (~50% of variance) by air mass exposure to uptake by Siberian and sub-arctic ecosystems. This resulted in an average 5 to 10 ppm difference with overlaying air masses. Stratosphere-troposphere exchange is found to strongly influence the observed O3 mixing ratios in spring, but not in summer. European emissions contributed to high O3 concentrations above Siberia in April 2006 and August 2007, while emissions from North Eastern China also contributed to higher O3 mixing ratios in summer, but tend to lower mixing ratios in spring, when the airmass aerosol burden is important. In the lower troposphere, large-scale deposition processes in the boreal and sub-arctic boundary layer is a large O3 sink, resulting in a ~20 ppb difference with overlaying air masses. Lagrangian footprint clustering is very promising and could also be advantageously applied to the interpretation of ground based measurements including calculation of tracers' sources and sinks.

scholarly journals AnANN Model Trained on Regional Data in the Prediction of Particular Weather Conditions

2021 ◽  
Vol 11 (11) ◽  
pp. 4757
Author(s):  
Aleksandra Bączkiewicz ◽  
Jarosław Wątróbski ◽  
Wojciech Sałabun ◽  
Joanna Kołodziejczyk
Keyword(s):  
Atmospheric Pressure ◽  
Real Life ◽  
Real Data ◽  
Weather Conditions ◽  
Maximum Temperature ◽  
Air Masses ◽  
Weather Forecasts ◽  
Life Problems ◽  
The World ◽  
The City

Artificial Neural Networks (ANNs) have proven to be a powerful tool for solving a wide variety of real-life problems. The possibility of using them for forecasting phenomena occurring in nature, especially weather indicators, has been widely discussed. However, the various areas of the world differ in terms of their difficulty and ability in preparing accurate weather forecasts. Poland lies in a zone with a moderate transition climate, which is characterized by seasonality and the inflow of many types of air masses from different directions, which, combined with the compound terrain, causes climate variability and makes it difficult to accurately predict the weather. For this reason, it is necessary to adapt the model to the prediction of weather conditions and verify its effectiveness on real data. The principal aim of this study is to present the use of a regressive model based on a unidirectional multilayer neural network, also called a Multilayer Perceptron (MLP), to predict selected weather indicators for the city of Szczecin in Poland. The forecast of the model we implemented was effective in determining the daily parameters at 96% compliance with the actual measurements for the prediction of the minimum and maximum temperature for the next day and 83.27% for the prediction of atmospheric pressure.

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