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DACCIWA Report Summary

Project ID: 603502
Funded under: FP7-ENVIRONMENT
Country: Germany

Periodic Report Summary 2 - DACCIWA (Dynamics-aerosol-chemistry-cloud interactions in West Africa)

Project Context and Objectives:
Southern West Africa (SWA) is currently experiencing unprecedented population and economic growth with concomitant impacts on land-use change and anthropogenic emissions. West Africa will continue to be in its demographic transition stage throughout the next decades. The current population of around 345 million is predicted to reach about 800 million by 2050 and be mostly urbanised. There will be increased industrialisation and demands for energy (biofuel, oil), leading to increases in atmospheric emissions. Already anthropogenic pollutants are thought to have tripled in SWA between 1950 and 2000 with similar increases expected by 2030. These dramatic changes will affect three areas of large socio-economic importance in a vulnerable region with complex human-ecosystem-climate impacts and feedbacks:
1) Human health: High concentrations of pollutants, particularly fine particles, in existing and evolving cities along the Guinea Coast including the mega-city of Lagos cause respiratory diseases with potentially large impacts on health costs and the capacity of the local work force. Environmental changes including atmospheric pollution have already significantly increased the cancer burden in Africa in recent years.
2) Regional ecosystem health, biodiversity and agricultural productivity: Anthropogenic emissions can lead to enhanced ozone production outside of urban conglomerations, which has detrimental effects on humans, animals, natural plants and crops. In SWA small-scale farming immediately downstream of big cities is an important element of food production, which would be seriously affected by high ozone concentrations. On a regional scale air quality is also seriously affected by biomass burning and natural dust aerosol.
3) Regional climate: Aerosol particles produced from biogenic and human emissions can change the climate and weather locally through their effects on radiation and clouds, which can modify the regional response to global climate change. Associated effects on temperature, rainfall and cloudiness can feedback on the land surface, ecosystems and crops and affect many other important socio-economic factors such as water availability, production systems, physical infrastructure and energy production, which relies on hydropower in many countries across SWA. At the moment our physical understanding of the West African monsoon (WAM) is limited and model predictions across a range of scales are uncertainty. This is partly due to the lack of sufficient long- and short-term observational data across the region.
The main objectives of DACCIWA are:
O1 Quantify the impact of multiple sources of anthropogenic and natural emissions, and transport and mixing processes on the atmospheric composition over SWA during boreal summer.
O2 Assess the impact of surface/lower-tropospheric atmospheric composition, in particular that of pollutants such as small particles and ozone, on human and ecosystem health and agricultural productivity, including possible feedbacks on emissions and surface fluxes.
O3 Quantify the two-way coupling between aerosols and cloud and raindrops, focusing on the distribution and characteristics of CCN, their impact on cloud characteristics and the removal of aerosol by precipitation.
O4 Identify controls on the formation, persistence and dissolution of low-level stratiform clouds, including processes such as advection, radiation, turbulence, latent-heat release, and how these influence aerosol impacts.
O5 Identify meteorological controls on precipitation, focusing on PBL development, the transition from stratus to convective clouds, entrainment and forcing from synoptic-scale weather systems.
O6 Quantify the impacts of low- and mid-level clouds (layered and deeper congestus) and aerosols on the radiation and energy budgets with a focus on effects of aerosols on cloud properties.
O7 Evaluate and improve state-of-the-art meteorological, chemistry and air-quality models as well as satellite retrievals of clouds, precipitation, aerosols and radiation in close collaboration with operational centres.
O8 Analyse the effect of cloud radiative forcing and precipitation on the West African monsoon circulation and water budget including possible feedbacks.
O9 Assess socio-economic implications of future changes in regional anthropogenic emissions, land use and climate for human and ecosystem health, agricultural productivity and water.
O10 Effectively disseminate research findings and data to policy-makers, scientists, operational centres, students, and the general public using a graded communication strategy.

Project Results:
The second phase of DACCIWA was dominated by the immediate preparation and successful conduction of the main field campaign in June-July 2016 in West Africa. This campaign had four main elements:
1) Ground-based supersites in Kumasi (Ghana), Savé (Benin) and Ile-Ife (Nigeria): Preparative actions included site visits, writing of a detailed operations plan, ample instrument testing, packing and shipping. After arrival in West Africa, instruments were brought to the respective sites, installed and tested. Some equipment from KIT was brought to Ile-Ife, where it was operated alongside Nigerian instruments. This was a major logistical challenge that involving difficult negotiations with African customs authorities. The instruments were operated continuously during most of June and July. Daily videoconferences were held to discuss weather forecasts and to coordinate Intensive Observation Periods. At the end, instruments were packed up and shipped back to Europe. The obtained dataset will be key to a better understanding of boundary-layer processes such as formation and breakdown of low-level jets and cloud decks, the surface energy balance and precipitation processes. In addition, a network of raingauges around Kumasi has been operated jointly by KNUST and KIT since 2014.
2) Radiosonde campaign: During June and July 2016, many additional radiosondes were launched from across West Africa: (a) at the supersites (see Point 1), (b) at sites of West African weather services operated through a subcontract with the African company AeroEquip (Abidjan, Cotonou, Parakou), (c) at additional sites operated by KIT together with African organisations (Accra, Lamto). To make this work, shipping of helium and other consumables to Africa had to be conducted, and equipment at existing stations were checked and if necessary updated. In total about 750 extra radiosondes were launched and will be key in analysing the vertical structure of the atmosphere at the regional level.
3) Aircraft campaign: The three research aircraft DLR Falcon, SAFIRE ATR42 and BAS TwinOtter were operated from the airport of Lomé (Togo) between 29 June and 15 July 2016, taking extensive measurements of cloud properties, trace gases, aerosols and meteorological parameters in a coordinated way. Several meetings were organised in Paris before and after the campaign to plan the complicated logistics (accommodation, travel, visa, permissions etc.) and the handling and analysis of data. A telecon-based Dry Run was conducted in June-July 2015 and an operations plan was written in spring 2016 to optimise flight-planning activities. During the campaign, daily meetings were held to monitor weather evolution and scientific objectives, discuss problems and plan future missions. Specific forecast products were made available through a dedicated webpage at
4) Urban campaign: Specific measurements of key emission sources (e.g. waste burning, traffic) were conducted in Abidjan and Cotonou. More health data were collected. These intensified measurements complement additional campaigns during the dry season and long-term measurements. These data will contribute to updated emission inventories and will be combined with model results and aircraft measurements.
Other activities not directly related to the field campaign include:
5) Digitisation of surface station data continued in collaboration with West African weather services and universities. These data are incorporated into an existing station database at KIT and made available to project partners.
6) Analysis of satellite data has continued, revealing some significant problems with standard products, e.g. those for estimated surface solar radiation. As flights during the campaign were coordinated with satellite overpasses and involved detailed radiation measurements, much more in-depth analysis of satellite products are now underway.
7) Modelling activities have advanced significantly at many DACCIWA partners, spanning the whole range from large-eddy models to climate simulations. The data collected in the field in 2016 will be key to evaluate these simulations and to conduct sensitivity studies.
8) Dissemination: Public events and press releases were organised around the main field campaign. An application for a special issue in Atmospheric Chemistry and Physics has been submitted. The webpage ( has been regularly updated and bi-annual newsletters were disseminated widely. A special DACCIWA session is planned for the EGU meeting in 2017. An article about the project’s main scientific motivation was published in Nature Climate Change (Knippertz et al. 2015).
Potential Impact:
1) A benchmark dataset
The lack of data in SWA currently impedes an advance of our scientific understanding and a rigorous evaluation of models and satellite retrievals. The DACCIWA field campaign and the provision of longer-term data through the digitalisation of surface observations, new satellite observations, air pollution monitoring and the collection of health statistics will have a large impact on our understanding of key processes. The data generated during DACCIWA will become a benchmark dataset for SWA used by a wide community of researchers.
2) Improved high-resolution and fully coupled modelling systems
Modelling centres around the world are now in the process of developing detailed atmospheric chemistry-aerosol and coupled cloud-aerosol schemes for operational and research models from the climate down to the weather scale and for air quality purposes. Advances in computing capabilities allow regional-scale, high-resolution simulations to be run over extensive periods, allowing much more complete cloud-aerosol couplings to be modelled and investigated. DACCIWA scientists are contributing to the improvement of operational models through process studies using a multi-scale, multi-complexity ensemble of different state-of-the-art modelling systems, which will be challenged with high-quality observations.
3) Scientific understanding
DACCIWA has already and will create further advances in the following areas:
• The rich mix of anthropogenic and natural emissions in SWA creates a highly complex chemical environment, with significant secondary organic and inorganic aerosol production coupled to air pollution, which is currently being characterised and analysed in great detail for the first time.
• DACCIWA is documenting the diurnal cycle over SWA in an unprecedented integral way combining detailed measurements of meteorological variables, surface energy fluxes, turbulence, atmospheric trace gases, aerosols, cloud microphysics and precipitation as well as high-resolution modelling experiments.
• Using ground sites and aircraft measurements, DACCIWA has sampled a range of surface and topographic conditions that allow an assessment of their influence on the local conditions.
• DACCIWA builds on new advances in cloud-aerosol understanding and modelling and applies them to a highly complex moist tropical region to challenge the existing knowledge obtained from other parts of the world, which allows our understanding to be refined and developed.
• DACCIWA contributes significantly to the dynamical understanding, observation, climatology and modelling of Guinea Coast rainfall systems, including their typical cloud structures.
• Through a combination of satellite, airborne and surface based radiation measurements with radiative transfer modelling, DACCIWA advances our understanding of effects of aerosol and clouds on the radiation and energy budgets.
• Using recently developed, sophisticated modelling tools evaluated with DACCIWA observations, key processes involved in complicated feedback chains between atmospheric composition and meteorology can be represented and is currently analysed for the first time.
• DACCIWA has begun studying the role of SWA for the continental-scale monsoon circulation, including forcings through radiative impacts of clouds and aerosols, latent-heat release and boundary-layer processes. It is expected that this can contribute to improving predictions of the WAM across temporal scales from weather to climate.
4) Socio-economic aspects, emission scenarios and policy-making
DACCIWA is creating advances in the following areas:
• DACCIWA has significantly expanded existing datasets on air pollution and medical data and places them into a regional context using aircraft and satellite data and high-resolution models as well as into a climatological context using new long-term observations.
• DACCIWA has collected sufficient aircraft observations to significantly advance our understanding of regional ozone levels and a range of chemistry models to assess their causes, impacts on ecosystems and agricultural productivity and possible mitigation strategies.
• Climate: In the longer run, DACCIWA will provide a comprehensive assessment of manmade regional climate change in SWA and estimate potential implications on water, energy and food production.
DACCIWA also generates updates and future projections for emission scenarios from SWA for international databases and climate modelling to design sustainable development strategies. DACCIWA has already and will communicate results through dedicated policy briefs and presentations to relevant stakeholders.
List of Websites:

Related information


Petra Witt, (Financial Officer)
Tel.: +49 721 60825421
Fax: +49 721 608 25403
Record Number: 199671 / Last updated on: 2017-06-21
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