Regional aerosol distribution and its long‐range transport over the Indian Ocean

Rajeev, K.; Ramanathan, V.; Meywerk, J.

doi:10.1029/1999jd900414

Cited by 123 publications

(105 citation statements)

References 33 publications

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“…Several studies have documented that aerosol concentration over the South Asian region progressively builds up during the dry season (October-April; e.g., Rajeev and Ramanathan 2002). The October-May distribution of the AI over the Indian Subcontinent reveals that the Indo-Gangetic plain is one of the areas with high loading of aerosols, the other areas being the Arabian Peninsula and the Taklamakan Desert.…”

Section: Toms Aerosol Index Variability Over the Indian Subcontinentmentioning

confidence: 99%

“…The Indian Ocean Experiment (INDOEX) revealed that a 3-km-thick brownish haze layer, composed of anthropogenic [up to 75% of the average aerosol optical depth (AOD)] (Lelieveld et al 2001) and natural aerosols, is spread over most of the tropical Indian Ocean toward the Himalayan region (Ramana et al 2004) and extends over Southeast Asia into the western Pacific (e.g., Rajeev et al 2000). INDOEX documented the persistence of the brown cloud for several months from winter to spring, its large black carbon (BC) content (up to 10%-14% of the total aerosol mass), and the large perturbation to the radiative energy budget of the region (up to Ϫ25 W m Ϫ2 in the mean clear-sky radiation at the surface).…”

Section: Introductionmentioning

confidence: 99%

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Absorbing Aerosols and Summer Monsoon Evolution over South Asia: An Observational Portrayal

2008

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The South Asian haze builds up from December to May, is mostly of anthropogenic origin, and absorbs part of the solar radiation. The influence of interannual variations of absorbing aerosols over the IndoGangetic Plain in May on the Indian summer monsoon is characterized by means of an observational analysis. Insight into how the aerosol impact is generated is also provided.It is shown that anomalous aerosol loading in late spring leads to remarkable and large-scale variations in the monsoon evolution. Excessive aerosols in May lead to reduced cloud amount and precipitation, increased surface shortwave radiation, and land surface warming. The June (and July) monsoon anomaly associated with excessive May aerosols is of opposite sign over much of the subcontinent (although with a different pattern) with respect to May. The monsoon strengthens in June (and July).The analysis suggests that the significant large-scale aerosol influence on monsoon circulation and hydroclimate is mediated by the heating of the land surface, pursuant to reduced cloudiness and precipitation in May. The finding of the significant role of the land surface in the realization of the aerosol impact is somewhat novel.

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Section: Toms Aerosol Index Variability Over the Indian Subcontinentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Absorbing Aerosols and Summer Monsoon Evolution over South Asia: An Observational Portrayal

2008

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“…It has also been shown that the pollution plume generally resulted from the mixing of air masses transported over long distances and whose aerosol characteristics were quite diverse (Rajeev et al, 2000;Lobert et al, 2002). Minvielle et al (2004a, b) have shown that the regional transport model could account for the long range transport and horizontal mixing.…”

Section: Introductionmentioning

confidence: 99%

The structure of the haze plume over the Indian Ocean during INDOEX: tracer simulations and LIDAR observations

et al. 2006

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Abstract. Three-dimensional, nested tracer simulations of a pollution plume originating from the Indian sub-continent over the Indian Ocean, in the framework of the Indian Ocean Experiment (INDOEX), between 5 and 9 March 1999, were performed with the Regional Atmospheric Modeling System (RAMS), to provide insight into the transport patterns of the pollutants, as well as to investigate the dynamical mechanisms controlling the vertical structure of the plume and its evolution in the vicinity of the Maldives Islands. Airborne and ground-based LIDAR observations of the structure of the haze plume made on 7 March 1999 were used to assess the quality of the simulations, as well as the impact of grid resolution on the vertical structure of the simulated plume. It is shown that, over the Arabian Sea, in the vicinity of the Maldives Islands, the pollutants composing the plume observed by the airborne LIDAR essentially originated from the city of Madras and that the vertical structure of the plume was controlled by the diurnal cycle of the continental boundary layer depth. A combination of tracer simulations and remote sensing observations (airborne LIDAR, ship-borne photometer, ground-based LIDAR in Goa) was used to analyse the diurnal evolution of the haze plume over the sea. We find evidence that the sea breeze circulation and orographic lifting taking place in the southern part of the Indian sub-continent during the daytime play a crucial role in the modulation of the continental boundary layer depth, and in turn, the haze plume depth. The eastward shift of the subtropical high from central India to the Bay of Bengal after 6 March lead to an increase in the tracer concentrations simulated over the Arabian Sea, in the region of intensive observations north of the Maldives, as transport pathways form Hyderabad and Madras were modified significantly. The nesting of a high horizontal resolution Correspondence to: G. Forêt (foret@lisa.univ-paris12.fr) domain (5 km, with 39 vertical levels below 4000 m above mean seal level) allows for a better representation of local dynamics, the circulation of sea and mountains breezes, and therefore a noticeable improvement in the representation of the pollutants' plume in the simulation.

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“…During the Asian winter monsoon period, the northeasterly winds from the land areas transport large amounts of continental aerosols over the oceanic regions [Rajeev et al, 2000]. This provides a unique opportunity to study the extent of transport of continental aerosols and their radiative impact over the otherwise pristine ocean areas.…”

Section: Introductionmentioning

confidence: 99%

“…The sensitivity of the derived AOD to surface reflectivity and aerosol single scattering albedo is shown by Rajeev et al [2000]. Figure 2 shows sensitivity of the derived AOD to the aerosol single scattering albedo (to), which is found to be the largest source of uncertainty.…”

Section: Introductionmentioning

confidence: 99%

Direct observations of clear‐sky aerosol radiative forcing from space during the Indian Ocean Experiment

Rajeev¹,

Ramanathan²

2001

J. Geophys. Res.

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Abstract. This study presents the regional estimates of the seasonal and diurnal mean broadband (0.3-5.0 •m) clear-sky aerosol radiative forcing at the top of atmosphere (TOA) due to both the natural and the anthropogenic aerosols over the tropical Indian Ocean from 25øN to 25øS. We propose two new methods, the slope method and the differencing method, to obtain clear sky aerosol forcing from solely satellite measurements. The focus of the study is January to March 1997, 1998, and 1999. The TOA clear-sky aerosol forcing was obtained by integrating satellite data for aerosol optical depth (AOD) and the broadband radiation budget. Over 30,000 pixels were collocated to

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Regional aerosol distribution and its long‐range transport over the Indian Ocean

Cited by 123 publications

References 33 publications

Absorbing Aerosols and Summer Monsoon Evolution over South Asia: An Observational Portrayal

Absorbing Aerosols and Summer Monsoon Evolution over South Asia: An Observational Portrayal

The structure of the haze plume over the Indian Ocean during INDOEX: tracer simulations and LIDAR observations

Direct observations of clear‐sky aerosol radiative forcing from space during the Indian Ocean Experiment

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