Atmospheric hazard in developing Countries: Risk assessment and Early Warning (ACREW) The overarching aim of ACREW is to develop the UK's capacity for building the resilience of developing countries to atmospheric hazards. The proposed programme of work will focus on two hazards:  air pollution and adverse weather - both of which disproportionately impact poor people.  Air pollution is a critical problem in many developing economies, reducing life expectancy by up to a decade, and GDP by up to 5% per year.   Weak infrastructure and dependence on rain fed agriculture render the populations of developing countries critically vulnerable to variation in the weather.    Recent technological and scientific developments offer opportunities to build the resilience of developing countries to hazards related both to air quality and to climate/weather.  In the case of air quality, new sensor technology promises a revolution in our ability to measure pollution on all scales, at low cost.  Reduced computing costs and readily available open-source software, furthermore, offer opportunities for scientists in developing countries to run their own air quality simulations.  In the case of climate and weather, newly available models, observational datasets and analysis tools have the potential to improve early warning of weather-related hazard on time-scales of days to seasons.   Users must, however, understand how much confidence can be placed in state-of-the-art models and technologies, if such systems are to be exploited safely in operational settings. This relies on sound scientific understanding of underpinning mechanisms, as well as on close engagement between researchers and end users.    All of the proposed work in ACREW contributes to the promotion of economic development and improved human welfare and health in developing countries. The specific activities have been chosen to exploit new scientific developments and existing expertise within NCAS. The air quality work packages (WPs) focus on the development of a new, affordable sensor for monitoring of air quality; liquid fuel composition and its effect on air pollution; and the formulation of evidence-based emissions policies through simulation of air quality in major cities.  The climate/weather WPs focus on early warning of agricultural drought; the risks associated with tropical cyclones; prediction of intense rainfall; and the utility of forecast information for managing complex systems, such as renewable energy supply and demand.  Each WP includes elements of science and application, although the balance varies depending on the activity.  Both the air quality and climate/weather components of ACREW include operational pilots of new technology, which will be carried out in partnership with on-the-ground organizations.  Strengthening and building of partnerships are key objectives for ACREW, and crucial for the project's success.  To this end, ACREW is centered round a series of workshops and exchange visits.  These engagement activities will cement collaborations and facilitate co-development of new technologies and research applications.  The participation of international organizations, such as the WMO, WHO, ECMWF and the Met Office in annual workshops will enhance the uptake ACREW scientific findings - widening impact beyond immediate project partnerships and pilots, and securing long-term development outcomes. The Global Challenges Research Fund (GCRF) supports cutting-edge research to address challenges faced by developing countries. The fund addresses the UN sustainable development goals. It aims to maximise the impact of research and innovation to improve lives and opportunity in the developing world.