scholarly journals Aerosols, clouds, and precipitation in the North Atlantic trades observed during the Barbados aerosol cloud experiment – Part 1: Distributions and variability

2016 ◽  
Vol 16 (13) ◽  
pp. 8643-8666 ◽  
Author(s):  
Eunsil Jung ◽  
Bruce A. Albrecht ◽  
Graham Feingold ◽  
Haflidi H. Jonsson ◽  
Patrick Chuang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
North Atlantic ◽  
Cloud Base ◽  
Cumulus Clouds ◽  
Air Masses ◽  
Shallow Marine ◽  
Cloud Radar ◽  
Aerosol Cloud ◽  
The North ◽  
The North Atlantic

Abstract. Shallow marine cumulus clouds are by far the most frequently observed cloud type over the Earth's oceans; but they are poorly understood and have not been investigated as extensively as stratocumulus clouds. This study describes and discusses the properties and variations of aerosol, cloud, and precipitation associated with shallow marine cumulus clouds observed in the North Atlantic trades during a field campaign (Barbados Aerosol Cloud Experiment- BACEX, March–April 2010), which took place off Barbados where African dust periodically affects the region. The principal observing platform was the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter (TO) research aircraft, which was equipped with standard meteorological instruments, a zenith pointing cloud radar and probes that measured aerosol, cloud, and precipitation characteristics.The temporal variation and vertical distribution of aerosols observed from the 15 flights, which included the most intense African dust event during all of 2010 in Barbados, showed a wide range of aerosol conditions. During dusty periods, aerosol concentrations increased substantially in the size range between 0.5 and 10 µm (diameter), particles that are large enough to be effective giant cloud condensation nuclei (CCN). The 10-day back trajectories showed three distinct air masses with distinct vertical structures associated with air masses originating in the Atlantic (typical maritime air mass with relatively low aerosol concentrations in the marine boundary layer), Africa (Saharan air layer), and mid-latitudes (continental pollution plumes). Despite the large differences in the total mass loading and the origin of the aerosols, the overall shapes of the aerosol particle size distributions were consistent, with the exception of the transition period.The TO was able to sample many clouds at various phases of growth. Maximum cloud depth observed was less than ∼ 3 km, while most clouds were less than 1 km deep. Clouds tend to precipitate when the cloud is thicker than 500–600 m. Distributions of cloud field characteristics (depth, radar reflectivity, Doppler velocity, precipitation) were well identified in the reflectivity–velocity diagram from the cloud radar observations. Two types of precipitation features were observed for shallow marine cumulus clouds that may impact boundary layer differently: first, a classic cloud-base precipitation where precipitation shafts were observed to emanate from the cloud base; second, cloud-top precipitation where precipitation shafts emanated mainly near the cloud tops, sometimes accompanied by precipitation near the cloud base. The second type of precipitation was more frequently observed during the experiment. Only 42–44 % of the clouds sampled were non-precipitating throughout the entire cloud layer and the rest of the clouds showed precipitation somewhere in the cloud, predominantly closer to the cloud top.

scholarly journals Aerosols, Clouds, and Precipitation in the North-Atlantic Trades Observed During the Barbados Aerosol Cloud Experiment. Part I: Distributions and Variability

2016 ◽  
Author(s):  
Eunsil Jung ◽  
Bruce A. Albrecht ◽  
Graham Feingold ◽  
Haflidi H. Jonsson ◽  
Patrick Chuang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
North Atlantic ◽  
Cloud Base ◽  
Cumulus Clouds ◽  
Air Masses ◽  
Shallow Marine ◽  
Cloud Radar ◽  
Aerosol Cloud ◽  
The North ◽  
The North Atlantic

Abstract. Shallow marine cumulus clouds are by far the most frequently observed cloud type over the Earth's oceans; but they are poorly understood and have not been investigated as extensively as stratocumulus clouds. This study describes and discusses the properties and variations of aerosol, cloud, and precipitation associated with shallow marine cumulus clouds observed in the North-Atlantic trades during a field campaign (Barbados Aerosol Cloud Experiment- BACEX, March–April, 2010), which took place off of Barbados where African dust periodically affects the region. The principal observing platform was the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter (TO) research aircraft, which was equipped with standard meteorological instruments, a zenith pointing cloud radar and probes that measured aerosol, cloud, and precipitation characteristics. The temporal variation and vertical distribution of aerosols observed from the 15 flights, which included the most intense African dust event during all of 2010 at Barbados, showed a wide range of aerosol conditions. During dusty periods, aerosol concentrations increased substantially in the size range between 0.5 μm and 10 μm (diameter), particles that large enough to be effective giant cloud condensation nuclei (CCN). The 10-day back trajectories showed three distinct air masses with distinct vertical structures associated with air masses originating in the Atlantic (typical maritime air mass with relatively low aerosol concentrations in the marine boundary layer), Africa (Saharan Air Layer), and mid-latitudes (continental pollution plumes). Despite the large differences in the total mass loading and the origin of the aerosols, the overall shapes of the aerosol particle size distributions were consistent, with the exception of the transition period. The TO was able to sample many clouds at various phases of growth. Maximum cloud depth observed was less than ~ 3 km, while most clouds were less than 1 km deep. Clouds tend to precipitate when the cloud is thicker than 500–600 m. Distributions of cloud field characteristics (depth, radar reflectivity, Doppler velocity, precipitation) were well identified in the reflectivity-velocity diagram from the cloud radar observations. Two types of precipitation features were observed for shallow marine cumulus clouds that may impact boundary layer differently: first, a classic cloud-base precipitation where precipitation shafts were observed to emanate from the cloud base; second, cloud-top precipitation where precipitation shafts emanated mainly near the cloud tops, sometimes accompanied by precipitation near the cloud base. The second type of precipitation was more frequently observed during the experiment. Only 42–44 % of the clouds sampled were non-precipitating throughout the entire cloud layer and the rest of clouds showed precipitation somewhere in the cloud, predominantly closer to the cloud top.

scholarly journals Ozone variability and halogen oxidation within the Arctic and sub-Arctic springtime boundary layer

2010 ◽  
Vol 10 (21) ◽  
pp. 10223-10236 ◽  
Author(s):  
J. B. Gilman ◽  
J. F. Burkhart ◽  
B. M. Lerner ◽  
E. J. Williams ◽  
W. C. Kuster ◽  
...  
Keyword(s):  
Boundary Layer ◽  
North Atlantic ◽  
Marine Boundary Layer ◽  
Transport Model ◽  
Arctic Basin ◽  
The Arctic ◽  
Arctic Boundary Layer ◽  
Air Masses ◽  
The North ◽  
The North Atlantic

Abstract. The influence of halogen oxidation on the variabilities of ozone (O3) and volatile organic compounds (VOCs) within the Arctic and sub-Arctic atmospheric boundary layer was investigated using field measurements from multiple campaigns conducted in March and April 2008 as part of the POLARCAT project. For the ship-based measurements, a high degree of correlation (r = 0.98 for 544 data points collected north of 68° N) was observed between the acetylene to benzene ratio, used as a marker for chlorine and bromine oxidation, and O3 signifying the vast influence of halogen oxidation throughout the ice-free regions of the North Atlantic. Concurrent airborne and ground-based measurements in the Alaskan Arctic substantiated this correlation and were used to demonstrate that halogen oxidation influenced O3 variability throughout the Arctic boundary layer during these springtime studies. Measurements aboard the R/V Knorr in the North Atlantic and Arctic Oceans provided a unique view of the transport of O3-poor air masses from the Arctic Basin to latitudes as far south as 52° N. FLEXPART, a Lagrangian transport model, was used to quantitatively determine the exposure of air masses encountered by the ship to first-year ice (FYI), multi-year ice (MYI), and total ICE (FYI+MYI). O3 anti-correlated with the modeled total ICE tracer (r = −0.86) indicating that up to 73% of the O3 variability measured in the Arctic marine boundary layer could be related to sea ice exposure.

scholarly journals Black carbon in the marine boundary layer over the North Atlantic and seas of the Russian arctic in june-september 2017

2019 ◽  
Vol 59 (5) ◽  
pp. 771-776
Author(s):  
V. P. Shevchenko ◽  
V. M. Kopeikin ◽  
A. N. Novigatsky ◽  
G. V. Malafeev
Keyword(s):  
Boundary Layer ◽  
Black Carbon ◽  
North Atlantic ◽  
Marine Boundary Layer ◽  
The Arctic ◽  
Air Masses ◽  
South Eastern ◽  
The North ◽  
The North Atlantic ◽  
Eastern Baltic

The paper presents the results of a study of the concentrations of black carbon in the marine boundary layer over the Baltic and North Seas, the North Atlantic, the Norwegian, the Barents, the Kara and the Laptev seas from June 30 to September 29, 2017 in the 68th and 69th voyages of research vessel "Akademik Mstislav Keldysh". Black carbon has a significant impact on climate change and the degree of pollution of the Arctic. Black carbon is formed as a result of incomplete combustion of fossil fuels (primarily coal, oil) and biomass or biofuel. It consists of submicron particles and their aggregates and can be transported a great distance from the source. Samples were taken by pumping air for 46 hours through quartz filters Hahnemule at an altitude of 10 m above sea level in a headwind to prevent smoke of the vessel from entering the filters. Subsequently, the black carbon content was determined in the laboratory by the aetalometric method. The backward trajectories of the air mass transfer and the black carbon particles transported by them to the sampling points were calculated using the HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model at http://www.arl.noaa.gov/ready.html. The conducted studies show low values of black carbon concentrations (50 ng/m3) along the expedition route when air masses came from the background areas of the North Atlantic and the Arctic. High concentrations of black carbon (100200 ng/m3 and higher) are characteristic for areas with active navigation (the South-Eastern Baltic, the North Sea) and near ports (eg Reykjavik), as well as for incoming air masses from the industrialized regions of Europe to South-Eastern Baltic and from areas of oil and gas fields where associated gas is flared (the North, the Norwegian and the Kara seas).

scholarly journals Ambient formaldehyde measurements made at a remote marine boundary layer site during the NAMBLEX campaign – a comparison of data from chromatographic and modified Hantzsch techniques

2005 ◽  
Vol 5 (6) ◽  
pp. 12531-12567 ◽  
Author(s):  
T. J. Still ◽  
S. Al-Haider ◽  
P. W. Seakins ◽  
R. Sommariva ◽  
J. C. Stanton ◽  
...  
Keyword(s):  
Boundary Layer ◽  
North Atlantic ◽  
Marine Boundary Layer ◽  
Direct Determination ◽  
Transport Processes ◽  
Chromatographic Technique ◽  
Air Masses ◽  
The North ◽  
The North Atlantic ◽  
Good Agreement

Abstract. Ambient formaldehyde concentrations are reported from the North Atlantic Marine Boundary Layer Experiment (NAMBLEX) campaign at Mace Head on the west coast of Ireland during August 2002. The results from two techniques, using direct determination via gas chromatography and the Hantzsch technique, show similar trends but a significant off set in concentrations. For westerly air flows characteristic of the marine boundary layer, formaldehyde concentrations from the gas chromatographic and Hantzsch technique ranged from 0.78–1.15 ppb and 0.13–0.43 ppb, respectively. Possible reasons for the discrepancy have been investigated and are discussed, however, no satisfactory explanation has yet been found. In a subsequent intercomparison the two techniques were in good agreement. The observed concentrations have been compared with previous formaldehyde measurements in the North Atlantic marine boundary layer and with other measurements from the NAMBLEX campaign. The measurements from the Hantzsch technique and the GC results lie at the lower and upper ends respectively of previous measurements. In contrast to some previous measurements, both techniques show distinct diurnal profiles with day maxima and with an amplitude of approximately 0.15 ppb. Strong correlations were observed with ethanal concentrations measured during NAMBLEX and the ratio of ethanal to formaldehyde determined by the gas chromatographic technique is in good agreement with previous measurements. Some simple box modelling has been undertaken to investigate possible sources of formaldehyde. Such models are not able to predict absolute formaldehyde concentrations as they do not include transport processes, but the results show that oxygenated VOCs such as ethanal and methanol are very significant sources of formaldehyde in the air masses reaching Mace Head.

scholarly journals Ozone variability and halogen oxidation within the Arctic and sub-Arctic springtime boundary layer

2010 ◽  
Vol 10 (6) ◽  
pp. 15885-15919 ◽  
Author(s):  
J. B. Gilman ◽  
J. F. Burkhart ◽  
B. M. Lerner ◽  
E. J. Williams ◽  
W. C. Kuster ◽  
...  
Keyword(s):  
Boundary Layer ◽  
North Atlantic ◽  
Marine Boundary Layer ◽  
Transport Model ◽  
Arctic Basin ◽  
The Arctic ◽  
Arctic Boundary Layer ◽  
Air Masses ◽  
The North ◽  
The North Atlantic

Abstract. The influence of halogen oxidation on the variabilities of ozone (O3) and volatile organic compounds (VOCs) within the Arctic and sub-Arctic atmospheric boundary layer was investigated using field measurements from multiple campaigns conducted in March and April 2008 as part of the POLARCAT project. For the ship-based measurements, a high degree of correlation (r=0.98 for 544 data points collected north of 68° N) was observed between the acetylene to benzene ratio, used as a marker for halogen oxidation, and O3 signifying the vast influence of bromine oxidation throughout the ice-free regions of the North Atlantic. Concurrent airborne and ground-based measurements in the Alaskan Arctic substantiated this correlation and were used to demonstrate that halogen oxidation influenced O3 variability throughout the Arctic boundary layer during these springtime studies. Measurements aboard the R/V "Knorr" in the North Atlantic and Arctic Oceans provided a unique view of the transport of O3-poor air masses from the Arctic Basin to latitudes as far south as 52° N. FLEXPART, a Lagrangian transport model, was used to quantitatively determine the exposure of air masses encountered by the ship to first-year ice (FYI), multi-year ice (MYI), and total ICE (FYI+MYI). O3 anti-correlated with the modeled total ICE tracer (r=−0.86) indicating that up to 73% of the O3 variability measured in the Arctic marine boundary layer could be related to sea ice exposure.

scholarly journals Ambient formaldehyde measurements made at a remote marine boundary layer site during the NAMBLEX campaign – a comparison of data from chromatographic and modified Hantzsch techniques

2006 ◽  
Vol 6 (9) ◽  
pp. 2711-2726 ◽  
Author(s):  
T. J. Still ◽  
S. Al-Haider ◽  
P. W. Seakins ◽  
R. Sommariva ◽  
J. C. Stanton ◽  
...  
Keyword(s):  
Boundary Layer ◽  
North Atlantic ◽  
Marine Boundary Layer ◽  
Direct Determination ◽  
Transport Processes ◽  
Chromatographic Technique ◽  
Air Masses ◽  
The North ◽  
The North Atlantic ◽  
Good Agreement

Abstract. Ambient formaldehyde concentrations are reported from the North Atlantic Marine Boundary Layer Experiment (NAMBLEX) campaign at Mace Head on the west coast of Eire during August 2002. The results from two techniques, using direct determination via gas chromatography and the Hantzsch technique, show similar trends but a significant off set in concentrations. For westerly air flows characteristic of the marine boundary layer, formaldehyde concentrations from the gas chromatographic and Hantzsch technique ranged from 0.78–1.15 ppb and 0.13–0.43 ppb, respectively. Possible reasons for the discrepancy have been investigated and are discussed, however, no satisfactory explanation has yet been found. In a subsequent laboratory intercomparison the two techniques were in good agreement. The observed concentrations have been compared with previous formaldehyde measurements in the North Atlantic marine boundary layer and with other measurements from the NAMBLEX campaign. The measurements from the Hantzsch technique and the GC results lie at the lower and upper ends respectively of previous measurements. In contrast to some previous measurements, both techniques show distinct diurnal profiles with day maxima and with an amplitude of approximately 0.15 ppb. Strong correlations were observed with ethanal concentrations measured during NAMBLEX and the ratio of ethanal to formaldehyde determined by the gas chromatographic technique is in good agreement with previous measurements. Some simple box modelling has been undertaken to investigate possible sources of formaldehyde. Such models are not able to predict absolute formaldehyde concentrations as they do not include transport processes, but the results show that oxygenated VOCs such as ethanal and methanol are very significant sources of formaldehyde in the air masses reaching Mace Head.

scholarly journals Composite analysis of the tropopause inversion layer in extratropical baroclinic waves

2019 ◽  
Vol 19 (10) ◽  
pp. 6621-6636 ◽  
Author(s):  
Thorsten Kaluza ◽  
Daniel Kunkel ◽  
Peter Hoor
Keyword(s):  
Sea Level ◽  
North Atlantic ◽  
Inversion Layer ◽  
Static Stability ◽  
Composite Analysis ◽  
Sea Level Pressure ◽  
Air Masses ◽  
Upper Troposphere ◽  
The North ◽  
The North Atlantic

Abstract. The evolution of the tropopause inversion layer (TIL) during cyclogenesis in the North Atlantic storm track is investigated using operational meteorological analysis data (Integrated Forecast System from the European Centre for Medium-Range Weather Forecasts). For this a total of 130 cyclones have been analysed during the months August through October between 2010 and 2014 over the North Atlantic. Their paths of migration along with associated flow features in the upper troposphere and lower stratosphere (UTLS) have been tracked based on the mean sea level pressure field. Subsets of the 130 cyclones have been used for composite analysis using minimum sea level pressure to filter the cyclones based on their strength. The composite structure of the TIL strength distribution in connection with the overall UTLS flow strongly resembles the structure of the individual cyclones. Key results are that a strong dipole in TIL strength forms in regions of cyclonic wrap-up of UTLS air masses of different origin and isentropic potential vorticity. These air masses are associated with the cyclonic rotation of the underlying cyclones. The maximum values of enhanced static stability above the tropopause occur north and northeast of the cyclone centre, vertically aligned with outflow regions of strong updraft and cloud formation up to the tropopause, which are situated in anticyclonic flow patterns in the upper troposphere. These regions are co-located with a maximum of vertical shear of the horizontal wind. The strong wind shear within the TIL results in a local minimum of Richardson numbers, representing the possibility for turbulent instability and potential mixing (or air mass exchange) within regions of enhanced static stability in the lowermost stratosphere.

Simulation of mid-latitude winter storms over the North Atlantic Ocean: impact of boundary layer parameterization schemes

2019 ◽  
Vol 53 (11) ◽  
pp. 6785-6814 ◽  
Author(s):  
P. K. Pradhan ◽  
Margarida L. R. Liberato ◽  
Vinay Kumar ◽  
S. Vijaya Bhaskara Rao ◽  
Juan Ferreira ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Winter Storms ◽  
Parameterization Schemes ◽  
The North ◽  
The North Atlantic

scholarly journals The North Atlantic Marine Boundary Layer Experiment(NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002

2006 ◽  
Vol 6 (8) ◽  
pp. 2241-2272 ◽  
Author(s):  
D. E. Heard ◽  
K. A. Read ◽  
J. Methven ◽  
S. Al-Haider ◽  
W. J. Bloss ◽  
...  
Keyword(s):  
Boundary Layer ◽  
North Atlantic ◽  
Marine Boundary Layer ◽  
Numerical Models ◽  
Measurement Data ◽  
Air Mass ◽  
The North ◽  
Trace Species ◽  
Wide Range ◽  
The North Atlantic

Abstract. The North Atlantic Marine Boundary Layer Experiment (NAMBLEX), involving over 50 scientists from 12 institutions, took place at Mace Head, Ireland (53.32° N, 9.90° W), between 23 July and 4 September 2002. A wide range of state-of-the-art instrumentation enabled detailed measurements of the boundary layer structure and atmospheric composition in the gas and aerosol phase to be made, providing one of the most comprehensive in situ studies of the marine boundary layer to date. This overview paper describes the aims of the NAMBLEX project in the context of previous field campaigns in the Marine Boundary Layer (MBL), the overall layout of the site, a summary of the instrumentation deployed, the temporal coverage of the measurement data, and the numerical models used to interpret the field data. Measurements of some trace species were made for the first time during the campaign, which was characterised by predominantly clean air of marine origin, but more polluted air with higher levels of NOx originating from continental regions was also experienced. This paper provides a summary of the meteorological measurements and Planetary Boundary Layer (PBL) structure measurements, presents time series of some of the longer-lived trace species (O3, CO, H2, DMS, CH4, NMHC, NOx, NOy, PAN) and summarises measurements of other species that are described in more detail in other papers within this special issue, namely oxygenated VOCs, HCHO, peroxides, organo-halogenated species, a range of shorter lived halogen species (I2, OIO, IO, BrO), NO3 radicals, photolysis frequencies, the free radicals OH, HO2 and (HO2+Σ RO2), as well as a summary of the aerosol measurements. NAMBLEX was supported by measurements made in the vicinity of Mace Head using the NERC Dornier-228 aircraft. Using ECMWF wind-fields, calculations were made of the air-mass trajectories arriving at Mace Head during NAMBLEX, and were analysed together with both meteorological and trace-gas measurements. In this paper a chemical climatology for the duration of the campaign is presented to interpret the distribution of air-mass origins and emission sources, and to provide a convenient framework of air-mass classification that is used by other papers in this issue for the interpretation of observed variability in levels of trace gases and aerosols.

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