Composition of the troposphere over the Indian Ocean during the monsoonal transition

Rhoads, Kevin P.; Kelley, Paul; Dickerson, Russell R.; Carsey, Thomas P.; Farmer, Michael L.; Savoie, Dennis L.; Prospero, Joseph M.

doi:10.1029/97jd01078

Cited by 78 publications

(98 citation statements)

References 42 publications

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“…21. These strong gradients, including the sharp gradient across the ITCZ, were first noted in measurements made on the pre-INDOEX and INDOEX ship cruises (e.g., Rhoads et al, 1997;Moorthy et al, 1997;Jayaraman et al, 1998Jayaraman et al, , 1999Jayaraman et al, , 2001Satheesh et al, 1998;Naja et al, 1999;Stehr et al, 2002;Quinn et al, 2002;Chand et al, 2001Chand et al, , 2003Kamra et al, 2003;Norman et al, 2003;Nair et al, 2004;Naja et al, 2004), as well as in aircraft observations during INDOEX (e.g., Ramanathan et al, 2001;Reiner et al, 2001;Gabriel et al, 2002a;Pelon et al, 2002;de Reus et al, 2002), and shortly thereafter were corroborated to be a general feature of the broader region based on numerous pieces of evidence, including further in situ observations, satellite retrievals and model simulations (e.g., Rajeev et al, 2000Rajeev et al, , 2004Rajeev and Ramanathan, 2001;Collins et al, 2001Collins et al, , 2002de Laat et al, 2001a, b;Lelieveld et al, 2001;Lawrence et al, 2003a;Minvielle et al, 2004a, b;Moorthy et al, 2005a;Satheesh et al, 2006a, b;Vinoj et al, 2007;Verma et al, 2008). In addition to this generally strong gradient of pollutants in the SAW-ABC, these observations and modeling studies have also shown a very abrupt transition between the polluted NH air masses and more pristine SH air in the MBL at the ITCZ, which can be considered a "chemical ITCZ" …”

Section: Transit Times Lofting In the Itcz And Interhemispheric Exchmentioning

confidence: 99%

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: Transit Times Lofting In the Itcz And Interhemispheric Exchmentioning

confidence: 99%

Atmospheric pollutant outflow from southern Asia: a review

2010

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“…Surface measurements of several trace gases, aerosols and meteorological parameters were made along with the soundings. For a detailed description and results of this campaign see Rhoads et al (1997) one year later in 1999. The Indian R/V Sagar Kanya sailed from southern India to the Indian Ocean east of Madagascar (Fig.…”

Section: Observationsmentioning

confidence: 99%

“…Generally, a typical O 3 profile over the Indian Ocean can be divided into several layers. In the marine boundary layer O 3 mixing ratios are low (outside of coastal regions), caused by an O 3 -destructive environment (Rhoads et al, 1997;Lal et al, 1998;de Laat and Lelieveld, 2000;Lawrence and Lal, 2001). Between the boundary layer and 8 km O 3 mixing ratios are higher.…”

Section: Introductionmentioning

confidence: 99%

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

Laat

2002

Atmos. Chem. Phys.

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Abstract. This study investigates the origin of a commonly observed feature in the O 3 profiles: mid tropospheric O 3 maxima (300-500 hPa) over the tropical Indian Ocean. A comparison and analysis of model simulations, using a 3-D global climate-chemistry model, and measured O 3 profiles from the INDOEX campaign is presented. European Centre for Medium-Range Weather Forecast (ECMWF) meteorological analyses have been assimilated into the 3-D model to represent actual meteorology. The model realistically simulates the observed mid-tropospheric O 3 maxima. The analysis of the model simulations shows that the major source of the mid-tropospheric O 3 maxima is advection of polluted air masses from continental biomass burning areas over Africa, with generally only a small contribution of stratospheric O 3 . Previous studies hinted at stratosphere-troposphere exchange (STE) along the subtropical jet (STJ) as the primary source of the mid-tropospheric O 3 maxima over the Indian Ocean. Analysis of the model simulations shows that the mechanism causing the mid-tropospheric transport of African biomass burning pollution and stratospheric air masses are frontal zones or waves passing along the subtropical jets, causing advection of tropical air masses in the prefrontal (equatorward) zone. Furthermore, the frontal zones or waves also cause STE at the poleward side of the STJ. The model simulations also indicate that the contribution of STE in general is minor compared to advection and in situ tropospheric production of O 3 for the mid-tropospheric O 3 budget over the Indian Ocean region.

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“…The diurnal variation of ozone observed over the oceanic environment is different from that observed over land as discussed in the earlier studies (Johnson et al, 1990;Rhoads et al, 1997;Bhugwant et al, 2001). Over the land, ozone shows an increase few hours after sunrise reaching peak values before noon and starts decreasing in the afternoon reaching low values at night (Lal et al, 2000;David and Nair, 2011).…”

Section: Diurnal Variation In Ozonementioning

confidence: 57%

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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Composition of the troposphere over the Indian Ocean during the monsoonal transition

Cited by 78 publications

References 42 publications

Atmospheric pollutant outflow from southern Asia: a review

Atmospheric pollutant outflow from southern Asia: a review

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

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

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Composition of the troposphere over the Indian Ocean during the monsoonal transition

Cited by 78 publications

References 42 publications

Atmospheric pollutant outflow from southern Asia: a review

Atmospheric pollutant outflow from southern Asia: a review

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

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

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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