Dimethyl sulfide: Less important than long-range transport as a source of sulfate to the remote tropical Pacific marine boundary layer

2014 ◽  
Vol 119 (14) ◽  
pp. 9142-9167 ◽  
Author(s):  
Rebecca M. C. Simpson ◽  
Steven G. Howell ◽  
Byron W. Blomquist ◽  
Antony D. Clarke ◽  
Barry J. Huebert
Keyword(s):  
Boundary Layer ◽  
Long Range ◽  
Dimethyl Sulfide ◽  
Marine Boundary Layer ◽  
Tropical Pacific ◽  
Long Range Transport ◽  
Range Transport

scholarly journals Free troposphere as a major source of CCN for the equatorial pacific boundary layer: long-range transport and teleconnections

2013 ◽  
Vol 13 (15) ◽  
pp. 7511-7529 ◽  
Author(s):  
A. D. Clarke ◽  
S. Freitag ◽  
R. M. C. Simpson ◽  
J. G. Hudson ◽  
S. G. Howell ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Long Range ◽  
Dimethyl Sulfide ◽  
Large Fraction ◽  
Equatorial Pacific ◽  
Long Range Transport ◽  
Quasi Equilibrium ◽  
Free Troposphere ◽  
Inter Tropical Convergence Zone ◽  
Range Transport

Abstract. Airborne aerosol measurements in the central equatorial Pacific during PASE (Pacific Atmospheric Sulfur Experiment) revealed that cloud condensation nuclei (CCN) activated in marine boundary layer (MBL) clouds were strongly influenced by entrainment from the free troposphere (FT). About 65% entered at sizes effective as CCN in MBL clouds, while ~25% entered the MBL too small to activate but subsequently grew via gas to particle conversion. The remaining ~10% were inferred to be sea salt aerosol. FT aerosols at low carbon monoxide (CO) mixing ratios (< 63 ppbv) were mostly volatile at 360 °C with a number mode peak of around 30–40 nm dry diameter and tended to be associated with cloud outflow from distant (3000 km or more) deep convection. Higher CO concentrations were commonly associated with trajectories from South America and the Amazon region (ca. ~10 000 km away) and occurred in layers indicative of combustion sources (biomass burning season) partially scavenged by precipitation. These had number modes near 60–80 nm dry diameter with a large fraction of CCN.2 (those activated at 0.2% supersaturation and representative of MBL clouds) prior to entrainment into the MBL. Flight averaged concentrations of CCN.2 were similar for measurements near the surface, below the inversion and in the FT just above the inversion, confirming that subsidence and entrainment of FT aerosol strongly influenced MBL CCN.2. Concurrent flight-to-flight variations of CCN.2 at all altitudes below 3 km also imply MBL CCN.2 concentrations were in quasi-equilibrium with the FT over a 2–3 day timescale. The observed FT transport over thousands of kilometers indicates teleconnections between MBL CCN and cloud-scavenged sources of both natural and/or residual combustion origin. Nonetheless, in spite of its importance, this source of CCN number is not well represented in most current models and is generally not detectable by satellite because of the low aerosol scattering in such layers as a result of cloud scavenging. In addition, our measurements confirm nucleation in the MBL was not evident during PASE and argue against a localized linear relation in the MBL between dimethyl sulfide (DMS) and CCN suggested by the CLAW hypothesis. However, when the FT is not impacted by long-range transport, sulfate aerosol derived from DMS pumped aloft in the ITCZ (Inter-Tropical Convergence Zone) can provide a source of CCN to the boundary layer via FT teleconnections involving more complex non-linear processes.

scholarly journals Impacts of long-range transport of aerosols on marine-boundary-layer clouds in the eastern North Atlantic

2020 ◽  
Vol 20 (23) ◽  
pp. 14741-14755
Author(s):  
Yuan Wang ◽  
Xiaojian Zheng ◽  
Xiquan Dong ◽  
Baike Xi ◽  
Peng Wu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Long Range ◽  
North Atlantic ◽  
Marine Boundary Layer ◽  
Long Range Transport ◽  
Vertical Profiles ◽  
Remote Region ◽  
Cloud Properties ◽  
Range Transport ◽  
Eastern North Atlantic

Abstract. Vertical profiles of aerosols are inadequately observed and poorly represented in climate models, contributing to the current large uncertainty associated with aerosol–cloud interactions. The US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) aircraft field campaign near the Azores islands provided ample observations of vertical distributions of aerosol and cloud properties. Here we utilize the in situ aircraft measurements from the ACE-ENA and ground-based remote-sensing data along with an aerosol-aware Weather Research and Forecast (WRF) model to characterize the aerosols due to long-range transport over a remote region and to assess their possible influence on marine-boundary-layer (MBL) clouds. The vertical profiles of aerosol and cloud properties measured via aircraft during the ACE-ENA campaign provide detailed information revealing the physical contact between transported aerosols and MBL clouds. The European Centre for Medium-Range Weather Forecasts Copernicus Atmosphere Monitoring Service (ECMWF-CAMS) aerosol reanalysis data can reproduce the key features of aerosol vertical profiles in the remote region. The cloud-resolving WRF sensitivity experiments with distinctive aerosol profiles suggest that the transported aerosols and MBL cloud interactions (ACIs) require not only aerosol plumes to get close to the marine-boundary-layer top but also large cloud top height variations. Based on those criteria, the observations show that the occurrence of ACIs involving the transport of aerosol over the eastern North Atlantic (ENA) is about 62 % in summer. For the case with noticeable long-range-transport aerosol effects on MBL clouds, the susceptibilities of droplet effective radius and liquid water content are −0.11 and +0.14, respectively. When varying by a similar magnitude, aerosols originating from the boundary layer exert larger microphysical influence on MBL clouds than those entrained from the free troposphere.

scholarly journals Long-range transport of ozone and related pollutants over the North Atlantic in spring and summer

2004 ◽  
Vol 4 (4) ◽  
pp. 4407-4454 ◽  
Author(s):  
S. A. Penkett ◽  
M. J. Evans ◽  
C. E. Reeves ◽  
K. S. Law ◽  
P. S. Monks ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Long Range ◽  
North Atlantic ◽  
Marine Boundary Layer ◽  
Long Range Transport ◽  
Ozone Concentrations ◽  
The North ◽  
Range Transport ◽  
The North Atlantic ◽  
The Uk

Abstract. This paper presents strong experimental evidence for a major perturbation in ozone concentrations over large parts of the North Atlantic Ocean from the surface to 8 km associated with continental pollutants. The evidence was gathered in the course of 7 flights by the UK Meteorological Office C-130 aircraft based on the Azores, and 4 ferry flights between the UK to the Azores in spring and summer 1997 as a component of the NERC-funded ACSOE project. The total latitude range covered was approximately 55°N–25°N, and the longitude range was approximately 0° to 40°W. Many profiles were made between the sea surface and altitudes up to 9 km to survey the composition of the marine atmosphere. The C-130 aircraft was comprehensively equipped to measure many chemical and physical parameters along with standard meteorological instrumentation. Thus it was able to measure ozone and speciated NOy, along with tracers including water vapour, carbon monoxide and condensation nuclei, in near real time. The overall "picture" of the troposphere over large parts of the North Atlantic is of layers of pollution from the continents of different ages interspersed with layers of air uplifted from the marine boundary layer. The lowest ozone concentrations were recorded in the marine boundary layer where there is evidence for extensive ozone destruction in summer. Flights were made to penetrate the outflow of hurricane Erica, to determine the southerly extent of polluted air in summer, to examine the impact of frontal systems on the composition of remote marine air, and to trace long-range pollution from the west coast of the USA interspersed with air with a stratospheric origin. In one of the spring flights it is possible that a plume of polluted air with high ozone and NOy, and with an origin in southeast Asia, was intercepted off the coast of Portugal. The concentrations of NOx, in this plume were sufficient for ozone formation to be continuing along its track from west to east. The instrument to measure NOy almost certainly was only measuring the sum of organic nitrates (mostly in the form of PAN) plus NOx. The high correlation between NOy and ozone under these conditions strongly suggests a non-stratospheric source for most of the ozone encountered over large parts of the atmosphere upwind of Europe. There was a marked seasonal variation in the NOy with about twice as much present in the spring flights than in the summer flights. The overall ozone levels in both spring and summer were somewhat similar although the highest ozone concentration encountered (~100 ppbv) was observed in summer in some polluted layers in mid Atlantic with an origin in the boundary layer over the southeastern USA. The bulk of the pollutants, ozone, CO, and NOy, were in the free troposphere at altitudes between 3 and 8 km. The only instances of pollution at lower levels were in the form of ship plumes, which were encountered several times. The data therefore strongly support the need for more in-situ aircraft experiments to quantify and understand the phenomenon of long-range transport of pollution from continent to continent. Observations at ground-based stations are inadequate for this purpose and satellite data is incomplete both in terms of its altitude detail and in the extent of chemical speciation, particularly for ascertaining whether chemical production and destruction processes for ozone are occurring.

scholarly journals Impacts of Long-range Transport of Aerosols on Marine Boundary Layer Clouds in the Eastern North Atlantic

2020 ◽  
Author(s):  
Yuan Wang ◽  
Xiaojian Zheng ◽  
Xiquan Dong ◽  
Baike Xi ◽  
Peng Wu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Long Range ◽  
North Atlantic ◽  
Marine Boundary Layer ◽  
Long Range Transport ◽  
Vertical Profiles ◽  
Remote Region ◽  
Cloud Properties ◽  
Range Transport ◽  
Eastern North Atlantic

Abstract. Vertical profiles of aerosols are inadequately observed and poorly represented in climate models, contributing to the current large uncertainty associated with aerosol-cloud interactions. The DOE ARM Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) aircraft field campaign near the Azores islands provided ample accurate observations of vertical distributions of aerosol and cloud properties. Here we utilize the in situ aircraft measurements from the ACE-ENA and ground-based remote sensing data along with an aerosol-aware Weather Research and Forecast (WRF) model to characterize the aerosols due to long-range transport over a remote region and to assess their possible influence on marine boundary-layer (MBL) clouds. The vertical profiles of aerosol and cloud properties measured via aircraft during the ACE-ENA campaign provide detailed information revealing the physical contact between transported aerosols and MBL clouds. The ECMWF-CAMS aerosol reanalysis data can reproduce the key features of aerosol vertical profiles in the remote region. The cloud-resolving WRF sensitivity experiments with distinctive aerosol profiles suggest that the transported aerosols and MBL cloud interactions (ACI) require not only low-altitude aerosol preferably getting close to the marine boundary layer top, but also large cloud top height variations. Based on those criteria, the observations show the occurrence of ACI involving the transport of aerosol over the Eastern North Atlantic is about 62 % in summer. For the case with noticeable long-range transport aerosol effect on MBL cloud, the susceptibilities of droplet effective radius and liquid water content are −0.11 and +0.14, respectively. When varying on the similar magnitude, aerosols originating from the boundary layer exert larger microphysical influence on MBL clouds than those entrained from free troposphere.

scholarly journals Atmospheric pollution over the eastern Mediterranean during summer – a review

2017 ◽  
Vol 17 (21) ◽  
pp. 13233-13263 ◽  
Author(s):  
Uri Dayan ◽  
Philippe Ricaud ◽  
Régina Zbinden ◽  
François Dulac
Keyword(s):  
Boundary Layer ◽  
Carbon Monoxide ◽  
Long Range ◽  
Mixed Layer ◽  
Air Pollutants ◽  
Asian Monsoon ◽  
Eastern Mediterranean ◽  
Long Range Transport ◽  
Range Transport ◽  
Ventilation Rates

Abstract. The eastern Mediterranean (EM) is one of the regions in the world where elevated concentrations of primary and secondary gaseous air pollutants have been reported frequently, mainly in summer. This review discusses published studies of the atmospheric dispersion and transport conditions characterizing this region during the summer, followed by a description of some essential studies dealing with the corresponding concentrations of air pollutants such as ozone, carbon monoxide, total reactive nitrogen, methane, and sulfate aerosols observed there. The interlaced relationship between the downward motion of the subsiding air aloft induced by global circulation systems affecting the EM and the depth of the Persian Trough, a low-pressure trough that extends from the Asian monsoon at the surface controlling the spatiotemporal distribution of the mixed boundary layer during summer, is discussed. The strength of the wind flow within the mixed layer and its depth affect much the amount of pollutants transported and determine the potential of the atmosphere to disperse contaminants off their origins in the EM. The reduced mixed layer and the accompanying weak westerlies, characterizing the summer in this region, led to reduced ventilation rates, preventing an effective dilution of the contaminants. Several studies pointing at specific local (e.g., ventilation rates) and regional peculiarities (long-range transport) enhancing the build-up of air pollutant concentrations are presented. Tropospheric ozone (O3) concentrations observed in the summer over the EM are among the highest over the Northern Hemisphere. The three essential processes controlling its formation (i.e., long-range transport of polluted air masses, dynamic subsidence at mid-tropospheric levels, and stratosphere-to-troposphere exchange) are reviewed. Airborne campaigns and satellite-borne initiatives have indicated that the concentration values of reactive nitrogen identified as precursors in the formation of O3 over the EM were found to be 2 to 10 times higher than in the hemispheric background troposphere. Several factors favor sulfate particulate abundance over the EM. Models, aircraft measurements, and satellite-derived data have clearly shown that sulfate has a maximum during spring and summer over the EM. The carbon monoxide (CO) seasonal cycle, as obtained from global background monitoring sites in the EM, is mostly controlled by the tropospheric concentration of the hydroxyl radical (OH) and therefore demonstrates high concentrations over winter months and the lowest concentrations during summer when photochemistry is active. Modeling studies have shown that the diurnal variations in CO concentration during the summer result from long-range CO transport from European anthropogenic sources, contributing 60 to 80 % of the boundary-layer CO over the EM. The values retrieved from satellite data enable us to derive the spatial distribution of methane (CH4), identifying August as the month with the highest levels over the EM. The outcomes of a recent extensive examination of the distribution of methane over the tropospheric Mediterranean Basin, as part of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx) program, using model simulations and satellite measurements, are coherent with other previous studies. Moreover, this methane study provides some insight into the role of the Asian monsoon anticyclone in controlling the variability of CH4 pollutant within mid-to-upper tropospheric levels above the EM in summer.

scholarly journals Atmospheric pollution concentrations over the Eastern Mediterranean during summer – A review

2017 ◽  
Author(s):  
Uri Dayan ◽  
Philippe Ricaud ◽  
Regina Zbinden ◽  
Francois Dulac
Keyword(s):  
Boundary Layer ◽  
Carbon Monoxide ◽  
Long Range ◽  
Mixed Layer ◽  
Air Pollutants ◽  
Asian Monsoon ◽  
Eastern Mediterranean ◽  
Long Range Transport ◽  
Range Transport ◽  
Ventilation Rates

Abstract. The Eastern Mediterranean (EM) is one of the regions in the world where elevated concentrations of primary and secondary gaseous air pollutants have been reported frequently, mainly in summer. This review discusses published studies of the atmospheric dispersion and transport conditions characterizing this region during the summer, followed by a description of some essential studies dealing with the corresponding concentrations of air pollutants such as ozone, carbon monoxide, total reactive nitrogen, methane and sulfate aerosols observed there. The interlaced relationship between the downward motion of the subsiding air aloft induced by global circulation systems affecting the EM and the depth of the Persian Trough, a low-pressure trough that extends from the Asian monsoon at the surface controlling the spatio-temporal distribution of the mixed boundary layer during summer is discussed. The strength of the wind flow within the mixed layer and its depth affect much the amount of pollutants transported and determine the potential of the atmosphere to disperse contaminants off their origins in the EM. The reduced mixed layer and the accompanying weak westerlies, characterizing the summer in this region, lead to reduced ventilation rates, preventing an effective dilution of the contaminants. Several studies pointing at specific local (e.g. ventilation rates) and regional peculiarities (long-range transport) enhancing the building up of pollutant concentrations are presented. Tropospheric ozone concentrations observed in the summer over the EM are among the highest over the Northern Hemisphere. The three essential processes controlling its formation (i.e., long- range transport of polluted air masses, dynamic subsidence at mid-tropospheric levels, and stratosphere-to-troposphere exchange) are reviewed. Airborne campaigns and satellite-borne initiatives have indicated that the concentration values of reactive nitrogen identified as precursors in the formation of ozone over the EM were found to be 2 to 10 times higher than in the hemispheric background troposphere. Several factors favor sulfate particulate abundance over the EM. Models, aircraft measurements, and satellite derived data, have clearly shown that sulfate has a maximum during spring and summer over the EM. The carbon monoxide (CO) seasonal cycle, as obtained from global background monitoring sites in the EM is mostly controlled by the tropospheric concentration of the hydroxyl radical (OH), and therefore demonstrates high concentrations over winter months and the lowest during summer when photochemistry is active. Modeling studies have shown that the diurnal variations in CO concentration during the summer result from long-range CO transport from European anthropogenic sources, contributing 60 to 80 % of the boundary-layer CO over the EM. The values retrieved from satellite data enable us to derive the spatial distribution of methane (CH4), identifying August as the month with the highest levels over the EM. The outcomes of a recent extensive examination of the distribution of methane over the tropospheric Mediterranean Basin, as part of the Chemical and Aerosol Mediterranean Experiment (ChArMEx) program, using model simulations and satellite measurements is coherent with other previous studies. Moreover, this methane study provides some insights on the role of the Asian monsoon anticyclone in controlling the variability of CH4 pollutant within mid-to-upper tropospheric levels above the EM in summer.

Modelling the-long-range transport of air pollutants with atmospheric boundary layer chemistry

1987 ◽  
Vol 41 (1-4) ◽  
pp. 407-416 ◽  
Author(s):  
George D. Djolov ◽  
Dimitar L. Yordanov ◽  
Dimitar E. Syrakov
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Long Range ◽  
Air Pollutants ◽  
Long Range Transport ◽  
Range Transport

scholarly journals Aerosol distribution in the northern Gulf of Guinea: local anthropogenic sources, long-range transport and the role of coastal shallow circulations

2018 ◽  
Author(s):  
Cyrille Flamant ◽  
Adrien Deroubaix ◽  
Patrick Chazette ◽  
Joel Brito ◽  
Marco Gaetani ◽  
...  
Keyword(s):  
Boundary Layer ◽  
West Africa ◽  
Long Range ◽  
Regional Scale ◽  
Lower Troposphere ◽  
Atmospheric Pollutants ◽  
Anthropogenic Sources ◽  
Long Range Transport ◽  
Aerosol Distribution ◽  
Range Transport

Abstract. The complex vertical distribution of aerosols over coastal southern West Africa (SWA) is investigated using airborne observations and numerical simulations. Observations were gathered on 2 July 2016 offshore of Ghana and Togo, during the field phase of the Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa project. The aerosol loading in the lower troposphere includes emissions from coastal cities (Accra, Lomé, Cotonou and Lagos) as well as biomass burning aerosol and dust associated with long-range transport from Central Africa and the Sahara, respectively. Our results indicate that the aerosol distribution is impacted by subsidence associated with zonal and meridional regional scale overturning circulations associated with the land-sea surface temperature contrast and orography over Ghana and Togo. Numerical tracer release experiments highlight the dominance of aged emissions from Accra on the observed pollution plume loadings over the ocean. The contribution of aged emission from Lomé and Cotonou is also evident above the marine boundary layer. Lagos emissions do not play a role for the area west of Cotonou. The tracer plume does not extend very far south over the ocean (i.e. less than 100 km from Accra), mostly because emissions are transported northeastward near the surface over land and westward above the marine atmospheric boundary layer. The latter is possible due to interactions between the monsoon flow, complex terrain and land-sea breeze systems, which support the vertical mixing of the urban pollution. This work sheds light on the complex – and to date undocumented – mechanisms by which coastal shallow circulations distribute atmospheric pollutants over the densely populated SWA region.

scholarly journals Injection in the lower stratosphere of biomass fire emissions followed by long-range transport: a MOZAIC case study

2008 ◽  
Vol 8 (6) ◽  
pp. 20925-20964
Author(s):  
J.-P. Cammas ◽  
J. Brioude ◽  
J.-P. Chaboureau ◽  
J. Duron ◽  
C. Mari ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Carbon Monoxide ◽  
Long Range ◽  
Source Region ◽  
Eastern Coast ◽  
Long Range Transport ◽  
Mixing Ratio ◽  
Fire Emissions ◽  
Range Transport

Abstract. This paper analyses a stratospheric injection by deep convection of biomass fire emissions over North America (Alaska, Yukon and Northwest Territories) on 24 June 2004 and its long-range transport over the eastern coast of the United States and the eastern Atlantic. The case study is done using MOZAIC observations of ozone, carbon monoxide, nitrogen oxides (NOx+PAN) and water vapour during the crossing of the southernmost tip of an upper level trough over the Eastern Atlantic on 30 June 03:00 UTC and 10:00 UTC and in a vertical profile over Washington DC on 30 June 17:00 UTC, and by lidar observations of aerosol backscattering at Madison (University of Wisconsin) on 28 June. Attribution of the plumes to the boreal fires is achieved by backward simulations with a Lagrangian particle dispersion model (FLEXPART). A simulation with the Meso-NH model for the source region shows that a boundary layer tracer, mimicking the boreal forest fire smoke, is lofted into the lowermost stratosphere (2–5 pvu layer) during the diurnal convective cycle. The isentropic levels (above 335 K) correspond to those of the downstream MOZAIC observations. The parameterized convective detrainment flux is intense enough to fill the volume of a model mesh (20 km horizontal, 500 m vertical) above the tropopause with pure boundary layer air in a time period compatible with the convective diurnal cycle, i.e. about 5 h. The maximum instantaneous detrainment fluxes deposited about 15–20% of the initial boundary layer tracer concentration at 335 K, which according to the 275-ppbv carbon monoxide maximum mixing ratio observed by MOZAIC over eastern Atlantic, would be associated with a 1.4–1.8 ppmv carbon monoxide mixing ratio in the boundary layer over the source region.

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