Distributions of O3, CO and hydrocarbons over the Bay of Bengal: A study to assess the role of transport from southern India and marine regions during September–October 2002

Sahu, L. K.; Lal, Shyam; Venkataramani, S.

doi:10.1016/j.atmosenv.2006.02.037

Cited by 46 publications

(54 citation statements)

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“…This is reflected in a clear dependence which was observed for the SO 2 concentration on the travel time since India (Norman et al, 2003). It can also be anticipated that the high OH levels will be important in the rapid oxidation of various hydrocarbons which have been observed to be present at significant levels in the SAW-ABC compared to rural continental observations, though much lower than observed in urban Indian regions (Mühle et al, 2002;Sahu et al, 2006;Lal et al, 2008b). Furthermore, rapid oxidation of SOA precursors may also lead to formation and growth of SOA, although we are unaware of any studies examining this issue specifically in the SAW-ABC.…”

Section: Gasesmentioning

confidence: 68%

“…On the other side of India, observations in the Arabian Sea during the withdrawal-MTP show clear anthropogenic fingerprints reappearing during October (Spencer et al, 2008): at MCOH, high-BC episodes occur during which over 70% of the particles show characteristics of originating from BMB + BFB, and most of the aerosol samples are also mixed with notable amounts of sulfate due to secondary processing during transport. Further observations made during the withdrawal MTP over both the Arabian Sea and the Bay of Bengal have shown similar trends towards reduced pollution levels with the shifts in the wind direction (e.g., Mandal et al, 2006;Sahu et al, 2006). One of the particularly interesting observations during the MTPs is the occasional, extremely strong influence of biomass burning in Indonesia on the eastern equatorial Indian Ocean during El Niño periods (Heil and Goldammer, 2001).…”

Section: The Monsoon Transition Period Plumesmentioning

confidence: 74%

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Atmospheric pollutant outflow from southern Asia: a review

2010

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Abstract. Southern Asia, extending from Pakistan and Afghanistan to Indonesia and Papua New Guinea, is one of the most heavily populated regions of the world. Biofuel and biomass burning play a disproportionately large role in the emissions of most key pollutant gases and aerosols there, in contrast to much of the rest of the Northern Hemisphere, where fossil fuel burning and industrial processes tend to dominate. This results in polluted air masses which are enriched in carbon-containing aerosols, carbon monoxide, and hydrocarbons. The outflow and long-distance transport of these polluted air masses is characterized by three distinct seasonal circulation patterns: the winter monsoon, the summer monsoon, and the monsoon transition periods. During winter, the near-surface flow is mostly northeasterly, and the regional pollution forms a thick haze layer in the lower troposphere which spreads out over millions of square km between southern Asia and the Intertropical Convergence Zone (ITCZ), located several degrees south of the equator over the Indian Ocean during this period. During summer, the heavy monsoon rains effectively remove soluble gases and aerosols. Less soluble species, on the other hand, are lifted to the upper troposphere in deep convective clouds, and are then transported away from the region by strong upper tropospheric winds, particularly towards northern Africa and the Mediterranean in the tropical easterly jet. Part of the pollution can reach the tropical tropopause layer, the gateway to the stratosphere. During the monsoon transition periods, the flow across the Indian Ocean is primarily zonal, and strong pollution plumes originating from both southeastern Asia and from Africa spread across the central Indian Ocean. This paper provides a review of the current state of knowledge based on the many observational and modeling studies over the last decades that have examined the southern AsianCorrespondence to: M. G. Lawrence (mark.lawrence@mpic.de) atmospheric pollutant outflow and its large scale effects. An outlook is provided as a guideline for future research, pointing out particularly critical issues such as: resolving discrepancies between top down and bottom up emissions estimates; assessing the processing and aging of the pollutant outflow; developing a better understanding of the observed elevated pollutant layers and their relationship to local sea breeze and large scale monsoon circulations; and determining the impacts of the pollutant outflow on the Asian monsoon meteorology and the regional hydrological cycle, in particular the mountain cryospheric reservoirs and the fresh water supply, which in turn directly impact the lives of over a billion inhabitants of southern Asia.

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Section: Gasesmentioning

confidence: 68%

Section: The Monsoon Transition Period Plumesmentioning

confidence: 74%

Atmospheric pollutant outflow from southern Asia: a review

2010

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“…This high variability is attributed to the relative source strengths over central and northern India as compared to southern India, highlighting the regional differences in CH 4 variability across India (Kavitha and Nair, 2016). Lal et al, 2007Lal et al, , 2006Nair et al, 2011;Srivastava et al, 2012;Sahu et al, 2006;and Mallik et al, 2013). Error bars show standard deviations for respective study periods.…”

Section: Seasonal Variation In Trace Gases Over the Bobmentioning

confidence: 99%

Variations in O<sub>3</sub>, CO, and CH<sub>4</sub> over the Bay of Bengal during the summer monsoon season: shipborne measurements and model simulations

et al. 2017

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Abstract. We present shipborne measurements of surface ozone (O 3 ), carbon monoxide (CO), and methane (CH 4 ) over the Bay of Bengal (BoB), the first time such measurements have been performed during the summer monsoon season, as a part of the Continental Tropical Convergence Zone (CTCZ) experiment during 2009. O 3 , CO, and CH 4 mixing ratios exhibited significant spatial and temporal variability in the ranges of 8-54 nmol mol −1 , 50-200 nmol mol −1 , and 1.57-2.15 µmol mol −1 , with means of 29.7 ± 6.8 nmol mol −1 , 96 ± 25 nmol mol −1 , and 1.83 ± 0.14 µmol mol −1 , respectively. The average mixing ratios of trace gases over BoB in air masses from central/northern India (O 3 : 30 ± 7 nmol mol −1 ; CO: 95 ± 25 nmol mol −1 ; CH 4 : 1.86 ± 0.12 µmol mol −1 ) were not statistically different from those in air masses from southern India (O 3 : 27 ± 5 nmol mol −1 ; CO: 101 ± 27 nmol mol −1 ; CH 4 : 1.72 ± 0.14 µmol mol −1 ). Spatial variability is observed to be most significant for CH 4 with higher mixing ratios in the air masses from central/northern India, where higher CH 4 levels are seen in the SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY) data. O 3 mixing ratios over the BoB showed large reductions (by ∼ 20 nmol mol −1 ) during four rainfall events. Temporal changes in the meteorological parameters, in conjunction with O 3 vertical profile, indicate that these low-O 3 events are associated with downdrafts of free-tropospheric O 3 -poor air masses. While the observed variations of O 3 and CO are successfully reproduced using the Weather Research and Forecasting model with Chemistry (WRF-Chem), this model overestimates mean concentrations by about 6 and 16 % for O 3 and CO, respectively, generally overestimating O 3 mixing ratios during the rainfall events. An analysis of modelled O 3 along air mass trajectories show mean en route O 3 production rate of about 4.6 nmol mol −1 day −1 in the outflow towards the BoB. Analysis of the various tendencies from model simulations during an event on 10 August 2009, reproduced by the model, shows horizontal advection rapidly transporting O 3 -rich air masses from near the coast across the BoB. This study fills a gap in the availability of trace gas measurements over the BoB and, when combined with data from previous campaigns, reveals large seasonal amplitude (∼ 39 and ∼ 207 nmol mol −1 for O 3 and CO, respectively) over the northern BoB.

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“…Moreover, this was the first time that direct measurements of NO 2 were carried out over this region. The earlier studies on ozone were conducted during the post-monsoon (September-October) and pre-monsoon/summer (FebruaryApril) months (Lal et al, , 2007Sahu et al, 2006). In view of this, the present study forms an extension to the above and brings out the seasonal variability.…”

Section: Introductionmentioning

confidence: 99%

“…Satellite measured column ozone and NO 2 values were used. The initial values of hydrocarbons were obtained by giving an enhancement of ∼30 % to the average values for the north and south BoB regions, which were measured in the monsoon season by Sahu et al (2006). For some of the species, initial conditions were generated by doing trial/sensitivity simulations.…”

Section: Box Model Simulationsmentioning

confidence: 99%

Distribution of ozone and its precursors over Bay of Bengal during winter 2009: role of meteorology

2011

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Abstract. Measurements of ozone and NO 2 were carried out in the marine environment of the Bay of Bengal (BoB) during the winter months, December 2008-January 2009, as part of the second Integrated Campaign for Aerosols, gases and Radiation Budget conducted under the Geosphere Biosphere Programme of the Indian Space Research Organization. The ozone mixing ratio was found to be high in the head and the southeast BoB with a mean value of 61 ± 7 ppb and 53 ± 6 ppb, respectively. The mixing ratios of NO 2 and CO were also relatively high in these regions. The spatial patterns were examined in the light of airflow patterns, air mass back trajectories and other meteorological conditions and satellite retrieved maps of tropospheric ozone, NO 2 , CO, and fire count in and around the region. The distribution of these gases was strongly associated with the transport from the adjoining land mass. The anthropogenic activities and forest fires/biomass burning over the Indo Gangetic Plains and other East Asian regions contribute to ozone and its precursors over the BoB. Similarity in the spatial pattern suggests that their source regions could be more or less the same. Most of the diurnal patterns showed decrease of the ozone mixing ratio during noon/afternoon followed by a nighttime increase and a morning high. Over this oceanic region, photochemical production of ozone involving NO 2 was not very active. Water vapour played a major role in controlling the variation of ozone. An attempt is made to simulate ozone level over the north and south BoB using the photochemical box model (NCAR-MM). The present observed features were compared with those measured during the earlier cruises conducted in different seasons.

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Distributions of O3, CO and hydrocarbons over the Bay of Bengal: A study to assess the role of transport from southern India and marine regions during September–October 2002

Cited by 46 publications

References 20 publications

Atmospheric pollutant outflow from southern Asia: a review

Atmospheric pollutant outflow from southern Asia: a review

Variations in O<sub>3</sub>, CO, and CH<sub>4</sub> over the Bay of Bengal during the summer monsoon season: shipborne measurements and model simulations

Distribution of ozone and its precursors over Bay of Bengal during winter 2009: role of meteorology

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Distributions of O3, CO and hydrocarbons over the Bay of Bengal: A study to assess the role of transport from southern India and marine regions during September–October 2002

Cited by 46 publications

References 20 publications

Atmospheric pollutant outflow from southern Asia: a review

Atmospheric pollutant outflow from southern Asia: a review

Variations in O&lt;sub&gt;3&lt;/sub&gt;, CO, and CH&lt;sub&gt;4&lt;/sub&gt; over the Bay of Bengal during the summer monsoon season: shipborne measurements and model simulations

Distribution of ozone and its precursors over Bay of Bengal during winter 2009: role of meteorology

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Variations in O<sub>3</sub>, CO, and CH<sub>4</sub> over the Bay of Bengal during the summer monsoon season: shipborne measurements and model simulations