Asian Brown Cloud

Asian Brown Cloud
Name	Asian Brown Cloud
Area	South Asia, Southeast Asia, East Asia
Formed	late 20th century (observed)
Causes	industrial emissions, biomass burning, vehicular pollution
Effects	reduced sunlight, air quality degradation, altered monsoon patterns

Asian Brown Cloud The Asian Brown Cloud is a large-scale haze layer observed across South Asia, Southeast Asia, and parts of East Asia that drew attention from agencies like the United Nations Environment Programme, research teams at institutions such as Indian Institute of Science, and international programs including the World Meteorological Organization and the Intergovernmental Panel on Climate Change. Scientists from National Aeronautics and Space Administration, European Space Agency, National Oceanic and Atmospheric Administration, and universities like Harvard University and University of Oxford have studied its aerosol composition using satellites such as MODIS and AIRS alongside field campaigns supported by organizations like Japan Aerospace Exploration Agency and China Meteorological Administration. Observations over regions including Indian subcontinent, Ganges, Indus River, Bay of Bengal, Himalayas, Tibetan Plateau, and Southeast Asia have linked the haze to emissions from sources associated with nations like India, China, Pakistan, Bangladesh, Nepal, Sri Lanka, and Myanmar.

Overview and Definition

Researchers characterize the phenomenon as a persistent, seasonal aerosol layer observed above surface plumes, identified in reports by United Nations Environment Programme, analyses by Royal Society, studies at NASA Goddard Institute for Space Studies, and assessments in journals such as Nature and Science. Satellite analyses by NOAA and ESA and in situ campaigns by institutions including CSIR and Peking University have differentiated the cloud from other haze events like those affecting Los Angeles, Beijing, and Mexico City, emphasizing its regional extent over the Indian Ocean and Arabian Sea. Historical comparisons reference air quality episodes recorded in archives from British India colonial records, observational networks run by Meteorological Department (India), and measurements coordinated with Global Atmosphere Watch.

Composition and Sources

Chemical analyses by teams from Columbia University, MIT, Indian Institute of Technology, Tata Institute of Fundamental Research, and National University of Singapore indicate a mixture of black carbon, organic carbon, sulfates, nitrates, dust, and secondary aerosols traced to activities in urban centers like Delhi, Mumbai, Chennai, Kolkata, Beijing, and Shanghai as well as agricultural regions in Punjab (India), Haryana, Sindh (Pakistan), and Mekong Delta. Emission inventories compiled by International Energy Agency and World Bank link contributions to coal combustion in power plants such as those managed by National Thermal Power Corporation and China National Energy Administration, biomass burning associated with crop residue practices in states like Punjab (India) and provinces like Yunnan, vehicular fleets registered with authorities like Transport Department (India), and open burning in regions including Sumatra and Borneo exacerbated by land-use change driven by corporations like PT Indofood and Kuala Lumpur Kepong. Aerosol fingerprinting studies by Lawrence Berkeley National Laboratory and Scripps Institution of Oceanography used isotopic markers and source apportionment tools developed at EPA and CSIRO.

Formation, Transport, and Seasonal Variability

Meteorological research by Indian Meteorological Department, National Center for Atmospheric Research, and European Centre for Medium-Range Weather Forecasts shows formation linked to emissions during dry seasons and transport governed by circulation features such as the South Asian monsoon, Himalayan foothill winds, and upper-tropospheric flows over the Bay of Bengal and Arabian Sea. Studies integrating reanalyses from ERA-Interim and MERRA-2 and trajectory modeling using tools from NOAA Air Resources Laboratory demonstrate seasonal peaks during pre-monsoon and post-harvest periods, with episodic injections into the free troposphere through convection over regions like Bengal, Myanmar, and Indochina Peninsula. Long-range transport events link emissions to transboundary impacts reaching the Tibetan Plateau, influenced by synoptic patterns documented in papers by Princeton University and University of Tokyo.

Environmental and Health Impacts

Epidemiological studies by World Health Organization, Public Health Foundation of India, Johns Hopkins University, Imperial College London, and University of California, Berkeley associate aerosol exposure with increased cardiopulmonary disease, stroke, and mortality in megacities such as Delhi, Dhaka, Lahore, and Karachi. Agricultural assessments by International Rice Research Institute, Food and Agriculture Organization, and CIMMYT indicate reductions in crop yields for staples like rice, wheat, and maize due to attenuated solar radiation, while cryosphere researchers at NIWA, University of Alaska Fairbanks, and Chinese Academy of Sciences report impacts on snowpack and glacier albedo in ranges like the Himalayas and Karakoram. Studies published in Proceedings of the National Academy of Sciences quantify radiative forcing effects with modeling groups at Hadley Centre, GISS, and Max Planck Institute for Meteorology evaluating climate perturbations.

Regional Climate and Monsoon Effects

Climate model intercomparisons coordinated through Coupled Model Intercomparison Project and analyses by Indian Institute of Tropical Meteorology, Met Office (UK), and NOAA Geophysical Fluid Dynamics Laboratory explore aerosol influences on the timing, intensity, and spatial distribution of the Indian monsoon, links to the El Niño–Southern Oscillation, and teleconnections to systems affecting East Asia and Australia. Research teams from Princeton University, National Taiwan University, and University of Hawaii have examined feedbacks between reduced surface insolation, sea-surface temperature anomalies in the Arabian Sea and Bay of Bengal, and shifts in monsoon onset that affect agricultural calendars managed by ministries such as Ministry of Agriculture & Farmers Welfare (India).

Monitoring, Measurement, and Modeling

Observational networks operated by AERONET, Global Atmosphere Watch, and national agencies including Indian Space Research Organisation, China National Space Administration, and Japan Meteorological Agency combine ground-based sunphotometers, lidar systems at observatories like Mahabaleshwar Observatory, and satellite retrievals from MODIS, MISR, CALIPSO, and AIRS. Modeling efforts utilize chemical transport models developed at NCAR, EMEP, and GEOS-Chem, with data assimilation frameworks from ECMWF and validation campaigns such as ABC (Asian Brown Cloud) project-era studies involving multidisciplinary teams from University of Delhi, Peking University, NASA Goddard, and European Commission institutes.

Mitigation, Policy, and International Response

Policy responses involve multilateral forums including United Nations Framework Convention on Climate Change, regional cooperation through South Asian Association for Regional Cooperation, national regulations enforced by entities like Central Pollution Control Board (India), and technological initiatives promoted by agencies such as International Renewable Energy Agency and Clean Air Initiative for Asian Cities. Programs targeting reductions in coal emissions, vehicle standards aligned with Euro emission standards, crop residue management promoted by ICRISAT and FAO, and reforestation projects supported by Green Climate Fund and Global Environment Facility are part of coordinated mitigation strategies evaluated in reports by World Bank, Asian Development Bank, and research consortia at Stanford University and Yale University.

Category:Air pollution in Asia