scholarly journals Connecting surface emissions, convective uplifting, and long-range transport of carbon monoxide in the upper troposphere: New observations from the Aura Microwave Limb Sounder

2007 ◽  
Vol 34 (18) ◽  
Author(s):  
Jonathan H. Jiang ◽  
Nathaniel J. Livesey ◽  
Hui Su ◽  
Lori Neary ◽  
John C. McConnell ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Long Range ◽  
Long Range Transport ◽  
Upper Troposphere ◽  
Range Transport

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 First simultaneous measurements of peroxyacetyl nitrate (PAN) and ozone at Nam Co in the central Tibetan Plateau: impacts from the PBL evolution and transport processes

2017 ◽  
Author(s):  
Xiaobin Xu ◽  
Hualong Zhang ◽  
Weili Lin ◽  
Ying Wang ◽  
Shihui Jia
Keyword(s):  
Long Range ◽  
Early Morning ◽  
Diurnal Variations ◽  
Long Range Transport ◽  
Nam Co ◽  
Monsoon Period ◽  
Air Masses ◽  
Upper Troposphere ◽  
Central Tibetan Plateau ◽  
Range Transport

Abstract. Both peroxyacetyl nitrate (PAN) and ozone (O3) are key photochemical products in the atmosphere. Most of the previous in-situ observations of both gases have been made in polluted regions and at low altitude sites. Here we present first simultaneous measurements of PAN and O3 at Nam Co (NMC, 90°57′ E, 30°46′ N, 4745 m  a.s.l.), a remote site in the central Tibetan Plateau (TP). The observations were made during summer periods in 2011 and 2012. The PAN concentrations averaged 0.36 ppb (range: 0.11–0.76 ppb) and 0.44 ppb (range: 0.21–0.99 ppb) during 16–25 August 2011 and 15 May to 13 July 2012, respectively. The O3 concentration varied from 27.9 ppb to 96.4 ppb, with an average of 60.0 ppb. Profound diurnal cycles of PAN and O3 were observed, with minimum values around 05:00 LT, steep rises in the early morning, and broader platforms of high values during 09:00–20:00 LT. We find that the evolution of planetary boundary layer (PBL) played a key role in shaping the diurnal patterns of both gases, particularly the rapid increases of PAN and O3 in the early morning. Air entrainment from the free troposphere into the PBL seemed to cause the early morning increase and be a key factor of sustaining the daytime high concentrations of both gases. The days with higher daytime PBL (about 3 km) showed stronger diurnal variations of both gases and were mainly distributed in the drier pre-monsoon period, while those with shallower daytime PBL (about 2 km) showed minor diurnal variations of both gases and were mainly distributed in the humid monsoon period. Episodes of higher PAN levels were observed occasionally at NMC. These PAN episodes were caused either by rapid downward transport of air masses from the middle/upper troposphere or by long-range transport of PAN plumes from North India. The PAN level in the downward transport cases ranged from 0.5 ppb to 0.7 ppb and may indicate the PAN abundance in the middle/upper troposphere. In the long-range transport case, the PAN level varied in the range of 0.6–1.0 ppb. This long-range transport process influenced most of the western and central TP region for about a week in early June 2012. Our results suggest that polluted air masses from South Asia can significantly enhance the PAN level over the TP. As PAN act as a reservoir of NOx, the impacts of pollution transport from South Asia on tropospheric photochemistry over the TP region deserve further studies.

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.

Long-range transport of ozone, carbon monoxide, and acidic trace gases at Oki Island, Japan, during PEM-WEST B/PEACAMPOT B campaign

1997 ◽  
Vol 102 (D23) ◽  
pp. 28637-28649 ◽  
Author(s):  
Yoshizumi Kajii ◽  
Hajime Akimoto ◽  
Yuichi Komazaki ◽  
Shigeru Tanaka ◽  
Hitoshi Mukai ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Long Range ◽  
Trace Gases ◽  
Long Range Transport ◽  
Range Transport

scholarly journals Ozone and carbon monoxide over India during the summer monsoon: regional emissions and transport

2016 ◽  
Vol 16 (5) ◽  
pp. 3013-3032 ◽  
Author(s):  
Narendra Ojha ◽  
Andrea Pozzer ◽  
Armin Rauthe-Schöch ◽  
Angela K. Baker ◽  
Jongmin Yoon ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Long Range ◽  
Summer Monsoon ◽  
Lower Troposphere ◽  
Southern India ◽  
Long Range Transport ◽  
Minor Role ◽  
Air Masses ◽  
Range Transport ◽  
Regional Emissions

Abstract. We compare in situ measurements of ozone (O3) and carbon monoxide (CO) profiles from the CARIBIC program with the results from the regional chemistry transport model (WRF-Chem) to investigate the role of local and regional emissions and long-range transport over southern India during the summer monsoon of 2008. WRF-Chem successfully reproduces the general features of O3 and CO distributions over the South Asian region. However, absolute CO concentrations in the lower troposphere are typically underestimated. Here we investigate the influence of local relative to remote emissions through sensitivity simulations. The influence of 50 % increased CO emissions over South Asia leads to a significant enhancement (upto 20 % in July) in upper tropospheric CO in the northern and central Indian regions. Over Chennai in southern India, this causes a 33 % increase in surface CO during June. However, the influence of enhanced local and regional emissions is found to be smaller (5 %) in the free troposphere over Chennai, except during September. Local to regional emissions are therefore suggested to play a minor role in the underestimation of CO by WRF-Chem during June–August. In the lower troposphere, a high pollution (O3: 146.4 ± 12.8, CO: 136.4 ± 12.2 nmol mol−1) event (15 July 2008), not reproduced by the model, is shown to be due to transport of photochemically processed air masses from the boundary layer in southern India. A sensitivity simulation combined with backward trajectories indicates that long-range transport of CO to southern India is significantly underestimated, particularly in air masses from the west, i.e., from Central Africa. This study highlights the need for more aircraft-based measurements over India and adjacent regions and the improvement of global emission inventories.

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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