The overarching aim of ACREW is to undertake research that builds thew 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. Within the Atmospheric hazard in developing Countries: Risk assessment and Early Warning (ACREW) project (2017-2020) NCAS has focused on two particular atmospheric hazards, working with local partners to translate cutting edge research into practical application. In this one-year extension to the ACREW project, we build on two key research themes - building new technological capability for air pollution measurement, and new predictive capability for meteorological hazards that impact the agriculture sectors, both with a focus on Africa. Although the research activities and partnerships involved in these two themes are scientifically distinct from one another, we work in an integrated way across NCAS to share best practice in ODA-related research, and where possible use our networks of partners in air quality and meteorological hazard to reach a boarder user audience. In the area of air pollution science we particularly focus in this one-year extension on the development of novel open-source measurement tools, building on recent breakthroughs made in sensor science and fabrication. In the area of meteorological hazards, we have identified a series of case studies as the focus, in order to maximise impact and sustain the partnerships developed in the earlier phases of ACREW. There is a long-standing critical gap in technological capability for quantifying air pollution in LMICs most recently highlighted by the 2019 UNICEF report "Silent suffocation in Africa". Existing monitoring equipment are not tolerant to unreliable power supplies, have high operational costs, high energy demand, and are very expensive to maintain in the long-term. Over the past three years ACREW has delivered new insight into the basic science of sustainable air-quality information in the world's poorest countries. NCAS has pioneered an entirely new concept for sustainable measurements exploiting the simplicity, modest cost and high reliability of state-of-the-art sensors and electronics, but drastically improving the quality of data collected by employing a multiplexed sensors measuring in an ensemble (or 'cluster'). We are seeking here to undertake research activities with the goal to create a field-tested scalable and practical solution for air quality measurement. This one-year extension will enable NCAS to focus efforts on co-designing, co-producing and field testing highly fault-tolerant sensor-based systems for air pollution measurement. In the previous stages of ACREW, improved meteorological prediction on sub-seasonal to seasonal (S2S) timescales has facilitated the development of new methodologies for assessing the risk of agricultural drought, tropical cyclones and extreme rainfall . New observations and reanalysis have, furthermore, elucidated potentially predictable large scale circulation regimes associated with wind energy supply in Central America. In all of the applications described above, risk assessment could be improved further by accounting for variation in prediction skill. For example, predictions of extreme rainfall may be more robust during particular phases of the MJO. Identification of windows of opportunity for robust prediction, and practical application for improved risk assessment will be the themes of the next phase of ACREW.