SWAAMI (South West Asian Aerosol Monsoon Interactions)

Lead Research Organisation: University of Manchester
Department Name: Earth Atmospheric and Env Sciences


Aerosol particles from pollution sources across the Indian subcontinent form a dense and extensive haze across India and the Bay of Bengal that increases in extent and magnitude in advance of the monsoon. As the aerosols, a large fraction of which arises from wood and charcoal fired cookstoves, absorb solar radiation as well as scatter it they can affect the heat balance of the lower atmosphere. It has been hypothesised that this aerosol can influence the monsoon through its role in redistribution of heat across the region in the pre-monsoon, and model studies have demonstrated that such effects can be important. However, current comparisons show model to model variability and under-prediction compared to observations, a strong indication that detailed aerosol properties are poorly represented in current models. The lack of accurate representation of aerosol in these models is compounded by a lack of measurements of sufficient accuracy and sensitivity to elucidate fundamental properties such as component mass, mixing state and optical properties, which need to be well characterised to improve model performance. This is limiting predictive capability at the present time and hence preventing the influence of aerosol in the Indian monsoon to be quantified. In addition to reproducing detailed properties of aerosol, models need to be able to accurately represent the horizontal and vertical distribution of different aerosols to predict their effects. As the monsoon progresses, pollution aerosol are removed by precipitation, but also lofted by convection. Dust advected from deserts to the west above the moist monsoonal flow become significant through the season. It is important that these aerosol layers are accurately represented in models and that robust measurements are available to rigorously challenge model predictions.

SWAAMI will contribute to the joint NERC-MoES programme "Drivers of Variability in the Asian Monsoon" through a detailed determination of aerosol physical and chemical properties across India in the advance of, and during, the Indian monsoon using UK and Indian research aircraft. The measurements will deliver a chemical and physical characterisation of the aerosol that is considerably more detailed than any previous and will enable assessment of aerosol composition and mixing state, provide source characterisation and deliver quantification of aerosol optical properties such as extinction, absorption and single scattering albedo. Such detailed characterisation will allow us to test representations of aerosol properties in regional and global climate models. Our planned aircraft measurements will be combined with syntheses of long term data from across the continent and previous field studies to provide a data set that can challenge how well models represent aerosol across the region. Improving model representations of aerosol properties and testing the extent to which this improves model performance against data will provide a framework for ensuring model aerosol schemes improve and in doing so will allow us to make more reliable predictions of aerosols effects on the heat budget of the region and hence improve our knowledge of how aerosols may influence the Indian monsoon.

Planned Impact

Regional climate variability and modification of regional weather, including precipitation, over a region as important as India is a highly significant social, political and scientific issue. The SWAAMI project will therefore have significant impact across a wide spectrum of stakeholders.
Who will benefit from this research?

Scientific community. This work will be of significant scientific interest nationally and internationally, in particular this work will benefit Indian and UK science and mutual benefit will be derived between SWAAMI and the wider MoES and NERC communities not just across the "Drivers of Variability in the Indian Monsoon" programme.

Operational Weather Forecasting Centres: SWAAMI is a direct collaboration with several research groups in the Met Office and will have a direct feed through to future improvements in Numerical Weather Prediction and Climate modelling.

General public/media. There has been significant publicity in recent years on aerosols, clouds and climate and also on India, pollution from cookstoves and the Indian monsoon and lastly on whether reducing black carbon emissions has the dual benefit of improving air quality and reducing regional and global warming. However, there remains significant lack of knowledge surrounding these issues and clear information needs to be conveyed to the public.

Policymakers: There is considerable interest from policy-makers on the impacts of absorbing aerosol on the radiative forcing of climate with suggestions for black carbon emission reduction as a mitigation strategy to counter global warming.

How will they benefit?
Scientific community. New ground based and airborne measurements over India will be important for the scientific community. Aerosol processes in models will be tested in an extremely important environment - the Indian subcontinent. Project results will be widely reported in publications, international conferences etc. Project results will feed into future IPCC assessments through modelling studies such as future equivalents of CMIP5 and AEROCOM.

Operational Weather Forecasting Centres: The UK Met Office is a key partner and beneficiary of SWAAMI science. The Met Office Observational Based Research Group will participate in the NERC-MoES experiment and has dedicated substantial flying hours to the project. The outcomes of the project will directly feed Met Office activities in the areas of Global Model Evaluation and Development, where SWAAMI will provide data to support the inclusion and testing of absorbing aerosols in operational Numerical Weather Prediction models. The Earth System and Mitigation Science Group will make use of SWAAMI outcomes to test its new aerosol scheme being developed within the Hadley Centre.

General public/media. Raising awareness of the role of absorbing aerosols and black carbon on regional climate and as a rapid solution for mitigating climate warming, in addition to improving air quality, will be performed by media interviews and press releases during the project. Articles for popular science magazines will also be produced. We will use podcasts and other web technologies to reach a wide audience. Local events such as national science week and presentations to local schools enhance the outreach from this project. We would hope to increase these opportunities to offer similar communication to people in India.

Policymakers: Project PIs have provided advice to the UK government, contributed to EU policy committees, as well as to IPCC and WMO panels and assessments. Many opportunities exist for SWAAMI scientists to raise awareness of the role of absorbing aerosols over India. In addition, project PDRAs will be encouraged to participate in the various 'science into policy' schemes that exist with the Royal Society and NERC. The measurement and modelling integration will provide policy makers with evidence for potential effectiveness of mitigation strategies.


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Gryspeerdt E (2020) Surprising similarities in model and observational aerosol radiative forcing estimates. in Atmospheric chemistry and physics

Description This work has provided the first information available to characterise pollution across northern India immediately in advance of and during the Indian monsoon through the atmosphere. This was possible by operating the UK research aircraft in India, the first time any international aircraft has done so. Key findings are: 1) pre-monsoon loadings across the Indo-Gangetic Plain are predominately organic in nature, probably arising from wood burning and also secondary organic aerosol. To the west in Rajasthan sulfate is the dominant aerosol. Long term measurements of aerosol composition have shown the importance of pollution aerosol flowing out towards the Bay of Bengal.
Exploitation Route through CEDA and via the international community through AEROCOM and IGAC for example
Sectors Environment,Government, Democracy and Justice,Transport

Description Indian partner - IISc 
Organisation Indian Institute of Science Bangalore
Country India 
Sector Academic/University 
PI Contribution Our team conducted research on the FAAM aircraft; analysed the data and ran UK regional and global climate models
Collaborator Contribution the IISc and VSSC team conducted research on a small aircraft, collected data from an extensive ground based network and have analysed the data and run Indian models
Impact none so far
Start Year 2015
Description VSSC - Indian Partner 
Organisation Vikram Sarabhai Space Centre
Country India 
Sector Public 
PI Contribution The SWAAMI UK team conducted measurements in india on the FAAM aircraft, analysed the data, and ran UK regional and global climate models
Collaborator Contribution The Indian partners made measurements on their own small aircraft, worked on the FAAM aircraft, collected data from a ground based network from across India and analysed it. They are running indian climate models.
Impact none yet
Start Year 2015
Description NERC Into the Blue 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact NERC Into the Blue - a week long event at Manchester Airport showcasing the FAAM aircraft and a wide range of NERC science
Year(s) Of Engagement Activity 2016
Description Press Conference and Tour of the FAAM aircraft by the Indian Minister for Science 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact A press conference was held at the end of the aircraft field programme at the operating base in Lucknow. The event was attended by the India Minister for Science who visited the aircraft. The meeting involved 200+ members of the international press.
Year(s) Of Engagement Activity 2016