Atmospheric pollutant outflow from southern Asia: a review

Lawrence, M. G.; Lelieveld, Jos

doi:10.5194/acp-10-11017-2010

Cited by 458 publications

(389 citation statements)

References 356 publications

(470 reference statements)

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“…Occasional air transport events from the mid-latitudes bring in higher ozone concentrations (Lawrence and Lelieveld, 2010). The mole fractions are low, typically 5-20 ppb, and the annual maximum occurs in June to September, southern winter, a characteristic of ozone in the Southern Hemisphere troposphere.…”

Section: Atmosmentioning

confidence: 99%

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

et al. 2015

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Abstract. Ozone holds a certain fascination in atmospheric science. It is ubiquitous in the atmosphere, central to tropospheric oxidation chemistry, yet harmful to human and ecosystem health as well as being an important greenhouse gas. It is not emitted into the atmosphere but is a byproduct of the very oxidation chemistry it largely initiates. Much effort is focused on the reduction of surface levels of ozone owing to its health and vegetation impacts, but recent efforts to achieve reductions in exposure at a country scale have proved difficult to achieve owing to increases in background ozone at the zonal hemispheric scale. There is also a growing realisation that the role of ozone as a short-lived climate pollutant could be important in integrated air quality climate change mitigation. This review examines current understanding of the processes regulating tropospheric ozone at global to local scales from both measurements and models. It takes the view that knowledge across the scales is important for dealing with air quality and climate change in a synergistic manner. The review shows that there remain a number of clear challenges for ozone such as explaining surface trends, incorporating new chemical understanding, ozone-climate coupling, and a better assessment of impacts. There is a clear and present need to treat ozone across the range of scales, a transboundary issue, but with an emphasis on the hemispheric scales. New observational opportunities are offered both by satellites and small sensors that bridge the scales.

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Section: Atmosmentioning

confidence: 99%

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

et al. 2015

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“…The significantly lower concentrations of both species during the monsoon reflected the combined influences of synoptic easterly airflow that transports a cleaner marine air mass over the region, reduced agricultural residue burning (Sarangi et al, 2014), and more efficient aerosol removal via wet deposition (Dumka et al, 2010). In addition to the possible active wet deposition of O 3 precursors during the monsoon season, increased cloudiness during monsoon may also reduce O 3 production (Lawrence and Lelieveld, 2010).…”

Section: Seasonal Variability In Bc and Omentioning

confidence: 99%

Transport of regional pollutants through a remote trans-Himalayan valley in Nepal

Dhungel

Kathayat²,

Mahata

et al. 2018

Atmos. Chem. Phys.

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Abstract. Anthropogenic emissions from the combustion of fossil fuels and biomass in Asia have increased in recent years. High concentrations of reactive trace gases and lightabsorbing and light-scattering particles from these sources form persistent haze layers, also known as atmospheric brown clouds, over the Indo-Gangetic plains (IGP) from December through early June. Models and satellite imagery suggest that strong wind systems within deep Himalayan valleys are major pathways by which pollutants from the IGP are transported to the higher Himalaya. However, observational evidence of the transport of polluted air masses through Himalayan valleys has been lacking to date. To evaluate this pathway, we measured black carbon (BC), ozone (O 3 ), and associated meteorological conditions within the Kali Gandaki Valley (KGV), Nepal, from January 2013 to July 2015. BC and O 3 varied over both diurnal and seasonal cycles. Relative to nighttime, mean BC and O 3 concentrations within the valley were higher during daytime when the up-valley flow (average velocity of 17 m s −1 ) dominated. BC and O 3 concentrations also varied seasonally with minima during the monsoon season (July to September). Concentrations of both species subsequently increased post-monsoon and peaked during March to May. Average concentrations for O 3 during the seasonally representative months of April, August, and November were 41.7, 24.5, and 29.4 ppbv, respectively, while the corresponding BC concentrations were 1.17, 0.24, and 1.01 µg m −3 , respectively. Up-valley fluxes of BC were significantly greater than down-valley fluxes during all seasons. In addition, frequent episodes of BC concentrations 2-3 times higher than average persisted from several days to a week during non-monsoon months. Our observations of increases in BC concentration and fluxes in the valley, particularly during pre-monsoon, provide evidence that trans-Himalayan valleys are important conduits for transport of pollutants from the IGP to the higher Himalaya.

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“…This location is influenced by the tropical/subtropical air mass exchanges and the sea breeze circulation (e.g., Lawrence and Lelieveld, 2010). The climate of AS can be divided into four different seasons, due to the seasonal variation in the ITCZ: winterspring monsoon (December-February), pre-monsoon transition (March-May), summer monsoon (June-August), and post-monsoon transition (September-November).…”

Section: Influences Of Meteorologymentioning

confidence: 99%

Tropospheric ozone maxima observed over the Arabian Sea during the pre-monsoon

Jia¹,

Ladstätter-Weißenmayer²,

Hou

et al. 2017

Atmos. Chem. Phys.

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Abstract. An enhancement of the tropospheric ozone column (TOC) over Arabian Sea (AS) during the pre-monsoon season is reported in this study. The potential sources of the AS spring ozone pool are investigated by use of multiple data sets (e.g., SCIAMACHY Limb-Nadir-Matching TOC, OMI/MLS TOC, TES TOC, MACC reanalysis data, MOZART-4 model and HYSPLIT model). Three-quarters of the enhanced ozone concentrations are attributed to the 0-8 km height range. The main source of the ozone enhancement is considered to be caused by long-range transport of ozone pollutants from India ( ∼ 50 % contributions to the lowest 4 km, ∼ 20 % contributions to the 4-8 km height range), the Middle East, Africa and Europe (∼ 30 % in total). In addition, the vertical pollution accumulation in the lower troposphere, especially at 4-8 km, was found to be important for the AS spring ozone pool formation. Local photochemistry, on the other hand, plays a negligible role in producing ozone at the 4-8 km height range. In the 0-4 km height range, ozone is quickly removed by wet deposition. The AS spring TOC maxima are influenced by the dynamical variations caused by the sea surface temperature (SST) anomaly during the El Niño period in 2005 and 2010 with a ∼ 5 DU decrease.

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Atmospheric pollutant outflow from southern Asia: a review

Cited by 458 publications

References 356 publications

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

Transport of regional pollutants through a remote trans-Himalayan valley in Nepal

Tropospheric ozone maxima observed over the Arabian Sea during the pre-monsoon

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