On the origin of tropospheric O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; over the Indian Ocean during the winter monsoon: African biomass burning vs. stratosphere-troposphere exchange

Laat, A. T. J. de

doi:10.5194/acp-2-325-2002

Cited by 11 publications

(13 citation statements)

References 47 publications

(62 reference statements)

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“…Offshore flowing air encounters a largely cloudfree northern Indian Ocean down to the equator. Typical travel times are about 7-10 days to reach the ITCZ (Ethé et al, 2002;de Gouw et al, 2001), where much of the air is then transported upwards in deep convective clouds. A nice demonstration of the typical flow patterns and variability during this period can be seen in the trajectories (Fig.…”

Section: Meteorological Setting Of Southern Asiamentioning

confidence: 99%

“…Due to this, O 3 was measured from nearly all platforms during the INDOEX IFP and pre-INDOEX campaigns, including at ground stations, onboard the ships, by balloon sondes, and on the aircraft (e.g., Rhoads et al, 1997;Mandal et al, 1999;Naja et al, 1999Naja et al, , 2004Chand et al, 2001Chand et al, , 2003Rao et al, 2001;Peshin et al, 2001;Lal and Lawrence, 2001;de Gouw et al, 2001;Williams et al, 2002;Stehr et al, 2002;Burkert et al, 2003;Ladstätter-Weissenmayer et al, 2007). Since then, data from satellite retrievals (e.g., Fishman et al, 2003;Ladstätter-Weissenmayer et al, 2007) and model simulations (de Laat et al, 2001a;Saraf et al, 2003) focused on analyzing ozone in this region, as well as other cruises in the Indian Ocean (e.g., Lal et al, 2006Lal et al, , 2007, have added to this information base.…”

Section: Gasesmentioning

confidence: 99%

“…This method was applied by Scheeren et al (2003), based on the measured ratios of CH 3 Cl, C 2 H 2 , CH 3 CN, and C 6 H 6 to CO in the Asian outflow during MINOS, and the assumption that the initial ratios could be taken from the INDOEX outflow measurements near the Indian coast de Gouw et al, 2001), with the exception of C 2 H 2 , for which the emission ratio to CO measured for fresh biomass burning was used. A chemical age of about 1-2 weeks is inferred from the measured ratios of both CH 3 Cl and C 6 H 6 to CO, and of 2-3 weeks based on C 2 H 2 and CH 3 CN, respectively.…”

Section: The Southern Asian Summer Monsoon Plume Over the Mediterraneanmentioning

confidence: 99%

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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: Meteorological Setting Of Southern Asiamentioning

confidence: 99%

Section: Gasesmentioning

confidence: 99%

Section: The Southern Asian Summer Monsoon Plume Over the Mediterraneanmentioning

confidence: 99%

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Atmospheric pollutant outflow from southern Asia: a review

2010

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“…Long‐range transport of the pollutants produces elevated concentrations of O 3 over the southern Atlantic Ocean [ Fishman et al , 1991, 1996; Thompson et al , 1996]. Pollutants are also transported from southern Africa over the Indian Ocean [ de Laat , 2002]. During transport, trace gases and particles can be transformed by photochemistry, gas‐to‐particle conversion, heterogeneous reactions, and particle coagulation [ Liousse et al , 1995; Hobbs et al , 1996, 2003; Goode et al , 2000; Yokelson et al , 2003; Gao et al , 2003].…”

Section: Introductionmentioning

confidence: 99%

Distributions of trace gases and aerosols during the dry biomass burning season in southern Africa

Sinha

2003

J. Geophys. Res.

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[1] Vertical profiles in the lower troposphere of temperature, relative humidity, sulfur dioxide (SO 2 ), ozone (O 3 ), condensation nuclei (CN), and carbon monoxide (CO), and horizontal distributions of twenty gaseous and particulate species, are presented for five regions of southern Africa during the dry biomass burning season of 2000. The regions are the semiarid savannas of northeast South Africa and northern Botswana, the savanna-forest mosaic of coastal Mozambique, the humid savanna of southern Zambia, and the desert of western Namibia. The highest average concentrations of carbon dioxide (CO 2 ), CO, methane (CH 4 ), O 3 , black particulate carbon, and total particulate carbon were in the Botswana and Zambia sectors (388 and 392 ppmv, 369 and 453 ppbv, 1753 and 1758 ppbv, 79 and 88 ppbv, 2.6 and 5.5 mg m À3 , and 13.2 and 14.3 mg m À3). This was due to intense biomass burning in Zambia and surrounding regions. The South Africa sector had the highest average concentrations of SO 2 , sulfate particles, and CN (5.1 ppbv, 8.3 mg m À3, and 6400 cm À3 , respectively), which derived from biomass burning and electric generation plants and mining operations within this sector. Air quality in the Mozambique sector was similar to the neighboring South Africa sector. Over the arid Namibia sector there were polluted layers aloft, in which average SO 2 , O 3 , and CO mixing ratios (1.2 ppbv, 76 ppbv, and 310 ppbv, respectively) were similar to those measured over the other more polluted sectors. This was due to transport of biomass smoke from regions of widespread savanna burning in southern Angola. Average concentrations over all sectors of CO 2 (386 ± 8 ppmv), CO (261 ± 81 ppbv), SO 2 (2.5 ± 1.6 ppbv), O 3 (64 ± 13 ppbv), black particulate carbon (2.3 ± 1.9 mg m À3 ), organic particulate carbon (6.2 ± 5.2 mg m À3 ), total particle mass (26.0 ± 4.7 mg m À3 ), and potassium particles (0.4 ± 0.1 mg m À3 ) were comparable to those in polluted, urban air. Since the majority of the measurements in this study were obtained in locations well removed from industrial sources of pollution, the high average concentrations of pollutants reflect the effects of widespread biomass burning. On occasions, relatively thin ($0.5 km) layers of remarkably clean air were located at $3 km above mean sea level, sandwiched between heavily polluted air. The data presented here can be used for inputs to and validation of regional and global atmospheric chemical models.

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“…De Laat, 2002;Chatfield et al, 2007;Lawrence and Lelieveld, 2010). In particular, O 3 peaks reaching 120 ppbv were often found in the UT within layers 1Á2 km thick just below the tropopause (De Laat et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

An upper tropospheric ‘ozone river’ from Africa to India during the 2008 Asian post-monsoon season

Tocquer

Barret

Mari

et al. 2015

Tellus B: Chemical and Physical Meteorology

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A B S T R A C TWe have used ozone data from the Infrared Atmospheric Sounding Interferometer to follow an event of ozoneenriched air-masses in the upper troposphere from eastern Africa to northern India. The ozone transport (hereafter called 'ozone river' or O3R) occurred during the Asian post-monsoon season in 2008 and was associated with Rossby wave propagation. The persistence of the O3R in a narrow channel was confirmed by MOZAIC airborne data over the northwestern Indian coast. The regions of origin of the O3R were identified by a transport analysis based on the Lagrangian model FLEXPART. The Lagrangian simulations combined with potential vorticity fields indicate that stratospheric intrusions are not likely to be the most important contributor to the observed O 3 enhancements. A high-resolution Eulerian model, Meso-NH, with tagged tracers was used to discriminate between African biomass burning, lightnings and Indian anthropogenic pollution as potential sources of precursors for the O3R. Lightning NOx emissions, associated with convective clouds over Africa, were found to be the principal contributor to the ozone enhancement over the Indian Ocean taking advantage of a northeastward jet. This case study illustrates African lightning emissions as an important source for enhanced O 3 in the upper troposphere over the Indian Ocean region during the post-monsoon season.

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On the origin of tropospheric O<sub>3</sub> over the Indian Ocean during the winter monsoon: African biomass burning vs. stratosphere-troposphere exchange

Cited by 11 publications

References 47 publications

Atmospheric pollutant outflow from southern Asia: a review

Atmospheric pollutant outflow from southern Asia: a review

Distributions of trace gases and aerosols during the dry biomass burning season in southern Africa

An upper tropospheric ‘ozone river’ from Africa to India during the 2008 Asian post-monsoon season

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