The direct observations of large aerosol radiative forcing in the Himalayan region

Ramana, M. V.; Ramanathan, V.; Podgorny, I. A.; Pradhan, Bidya Banmali; Shrestha, Basanta

doi:10.1029/2003gl018824

Cited by 115 publications

(96 citation statements)

References 20 publications

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“…11210 G. P. Gobbi et al: Sunphotometry 2006 at the Himalayan EvK2-CNR station (5079 m a.s.l.) Central Himalayas (Pant et al, 2006), and in Nepal (Ramana et al, 2004). A positive forcing was also observed in the aerosol-laden air proceeding from the Indian continent to the Maldives during the pre-monsoon (biomass burning) season, and proposed as a possible cause for the observed retreat of the Himalayan glaciers (Ramanathan et al, 2007a).…”

Section: Introductionmentioning

confidence: 88%

Sunphotometry of the 2006–2007 aerosol optical/radiative properties at the Himalayan Nepal Climate Observatory-Pyramid (5079 m a.s.l.)

et al. 2010

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Abstract. In spite of being located at the heart of the highest mountain range in the world, the Himalayan Nepal Climate Observatory (5079 m a.s.l.) at the Ev-K2-CNR Pyramid is shown to be affected by the advection of pollution aerosols from the populated regions of southern Nepal and the Indo-Gangetic plains. Such an impact is observed along most of the period April 2006-March 2007 addressed here, with a minimum in the monsoon season. Backtrajectoryanalysis indicates long-range transport episodes occurring in this year to originate mainly in the west Asian deserts. At this high altitude site, the measured aerosol optical depth is observed to be about one order of magnitude lower than the one measured at Ghandi College (60 m a.s.l.), in the IndoGangetic basin. As for Ghandi College, and in agreement with the in situ ground observations at the Pyramid, the fine mode aerosol optical depth maximizes during winter and minimizes in the monsoon season. Conversely, total optical depth maximizes during the monsoon due to the occurrence of elevated, coarse particle layers. Possible origins of these particles are wind erosion from the surrounding peaks and hydrated/cloud-processed aerosols. Assessment of the aerosol radiative forcing is then expected to be hampered by the presence of these high altitude particle layers, which impede an effective, continuous measurement of anthropogenic aerosol radiative properties from sky radiance inversions and/or ground measurements alone. Even though the retrieved absorption coefficients of pollution aerosols were rather large (single scattering albedo of the order of Correspondence to: G. P. Gobbi (g.gobbi@isac.cnr.it) 0.6-0.9 were observed in the month of April 2006), the corresponding low optical depths (∼0.03 at 500 nm) are expected to limit the relevant radiative forcing. Still, the high specific forcing of this aerosol and its capability of altering snow surface albedo provide good reasons for continuous monitoring.

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Section: Introductionmentioning

confidence: 88%

Sunphotometry of the 2006–2007 aerosol optical/radiative properties at the Himalayan Nepal Climate Observatory-Pyramid (5079 m a.s.l.)

et al. 2010

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“…It has been demonstrated clearly (e.g., Ramana et al, 2004;Di Girolamo et al, 2004;Ramanathan and Ramana, 2005; see Lawrence and Lelieveld, 2010 for a review of the South Asian pollution problem) that the entire IGP region is subject to dense layer of atmospheric brown clouds (ABCs; consisting of BC, OC, sulfates and other aerosols) whose concentration varies with the season, reaching peak values during the dry season (November to March).…”

Section: The Large Scale Context Of the Observationsmentioning

confidence: 99%

Black carbon emissions from biomass and fossil fuels in rural India

et al. 2011

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Abstract. Black carbon (BC) emission from biofuel cooking in South Asia and its radiative forcing is a significant source of uncertainty for health and climate impact studies. Quantification of BC emissions in the published literature is either based on laboratory or remote field observations far away from the source. For the first time under Project Surya, we use field measurements taken simultaneously inside rural households, ambient air and vehicular emissions from highways in a rural area in the Indo-Gangetic-Plains region of India to establish the role of both solid biomass based cooking in traditional stoves and diesel vehicles in contributing to high BC and organic carbon (OC), and solar absorption. The major finding of this study is that BC concentrations during cooking hours, both indoors and outdoors, have anomalously large twice-daily peak concentrations reaching 60 µg m −3 (median 15-min average value) for indoor and 30 µg m −3 (median 15-min average value) for outdoor during the early morning (05:00 to 08:00) and early evening (17:00 to 19:00) hours coinciding with the morning and evening cooking hours. The BC during the non-cooking hours were also large, in the range of 2 to 30 µg m −3 . The peak indoor BC concentrations reached as high as 1000 µg m −3 . The large diurnal peaks seen in this study lead to the conclusion that satellite based aerosol studies that rely on once-daily daytime measurements may severely underestimate the BC loading of the atmosphere. The concentration of OC was a factor of 5 larger than BC and furthermore optical data show that absorbing brown carbon was a major component of the OC. The imprint of the cooking hour peaks were seen in the outdoor BC both in the village as well as in the highway. The results have significant implications for climate and epidemiological studies.

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“…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%

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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The direct observations of large aerosol radiative forcing in the Himalayan region

Cited by 115 publications

References 20 publications

Sunphotometry of the 2006–2007 aerosol optical/radiative properties at the Himalayan Nepal Climate Observatory-Pyramid (5079 m a.s.l.)

Sunphotometry of the 2006–2007 aerosol optical/radiative properties at the Himalayan Nepal Climate Observatory-Pyramid (5079 m a.s.l.)

Black carbon emissions from biomass and fossil fuels in rural India

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

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