atmospheric brown clouds
DESCRIPTION
Atmospheric brown clouds (ABCs) are smog like regional scale plumes of air pollution(brown haze >1 mile thick) that consist of copious amounts of tiny particles of soot, sulphates, nitrates, fly ash and many other pollutants caused mainly by the burning of fossil fuels and firewood ABCs start as indoor and outdoor air pollution consisting of particles (referred to as primary aerosols) and pollutant gases, such as NOx, CO, SO2, NH3, and hundreds of organic gases and acids. First observation (1990) global phenomenon and are associated with human-generated air pollutionTRANSCRIPT
1
ATMOSPHERIC BROWN CLOUDS
Xarrin Sindhu
2
INTRODUCTION
Atmospheric brown clouds (ABCs) are smog like regional scale plumes of air pollution(brown haze >1 mile thick) that consist of copious amounts of tiny particles of soot, sulphates, nitrates, fly ash and many other pollutants caused mainly by the burning of fossil fuels and firewood
ABCs start as indoor and outdoor air pollution consisting of particles (referred to as primary aerosols) and pollutant gases, such as NOx, CO, SO2, NH3, and hundreds of organic gases and acids.
First observation (1990) global phenomenon and are associated with
human-generated air pollution
3
EMERGING CLIMATE ISSUE
Atmospheric brown clouds are caused by emissions associated with the combustion of fossil fuels and biomass.
consisting of mainly aerosol particles, such as black carbon (BC), and precursor gases which produce aerosols and ozone.
4
EFFECTS
aerosols in ABC reduce the amount of sunlight reaching the Earth’s surface by as much as 10 to 15%
enhance atmospheric solar heating by as much as 50%.
ABCs, on the one hand, mask the greenhouse warming by the surface dimming
On the other hand enhance the greenhouse warming of the atmosphere.
While confirming that ABCs may have masked global warming by as much as 50%
5
ABC EFFECT ON REGIONAL CLIMATE
Slowing down of the monsoon circulation and reduction in monsoon rainfall.
Increase strength and frequency of winter and spring time temperature inversion.
Enhancing the greenhouse warming of the atmosphere thus contributing to glacier melting.
Impacts on precipitation patterns and water budgets
Impacts on agriculture Impacts on human health
6
ABC HOTSPOTS
found in all densely inhabited regions and oceanic regions
Five regional ABC hotspots around the world have been identified:
i) East Asia ii) Indo-Gangetic Plain in South Asia iii) Southeast Asia iv) Southern Africa; and v) the Amazon Basin.
7
HOTSPOT?
ABC hotspots are defined as regions where the annual mean anthropogenic aerosol optical depth (AOD) exceeds 0.3 and the percentage of contribution by absorbing aerosols exceeds 10 per cent (absorbing AOD > 0.03)
8
ABCS INFLUENCE CLOUD PROPERTIES
Aerosols in ABCs nucleate cloud drops. cloud drop size decreases Cloud lifetime extended in polluted areas
9
ABCS RADIATIVE FORCING
ABCs have significantly altered this radiative forcing over Asia
Caused dimming at the surface. soot in ABCs has increased solar heating of
the atmosphere.
10
AGRICULTURE INFLUENCE
Decrease wheat/rice yield upto 7-8 % as predicted by simulative models
No effect on sugarcane crop predicted
11
HEALTH EFFECTS
cardiovascular and pulmonary effects leading to chronic respiratory problems, hospital admissions and deaths.
12
REFERENCES
Ramanathan, V., Chung, C., Kim, D., Bettge, T., Buja, L., Kiehl, J.T., Washington, W.M., Fu, Q., Sikka, D.R. and Wild, M. (2005). Atmospheric brown clouds: Impacts on South Asian climate and hydrological cycle. In Proc. Natl. Acad. Sci. 102:5326-5333
http://www.britannica.com/EBchecked/topic/1532857/atmospheric-brown...
http://www.rrcap.unep.org/abc/
