As climate has warmed in response to increasing greenhouse gases, the distribution of Arctic sea ice has changed dramatically, becoming thinner over large portions of the Arctic Ocean basin in summer with a prominent reduction of the September minimum in sea ice extent. Human activity is increasing within the Arctic as the environment changes, with more residents and visitors making use of the increased window for shipping, offshore operations and tourism during summer. This has driven demand for coupled forecasts of weather, ocean and sea-ice state across the Arctic on the timescales needed to make risk-based decisions. Weather forecast skill for the Arctic is lower than for northern mid-latitudes, but the reasons why are multi-faceted and not fully known. Our hypothesis is that some aspects of the Arctic environment are not well forecast because the surface conditions beneath Arctic weather systems are more dynamic due to the movement of sea ice. Understanding of the physical processes that couple the atmosphere, ocean and sea ice is incomplete and the new frontier in prediction is to model this coupled system with fidelity and skill. Centres striving to improve capability in this area are our project partners: the Met Office, ECMWF and Met Norway. Arctic cyclones are the dominant type of hazardous weather system affecting the Arctic environment in summer - thus a concern for all human activities. They can also have critical impacts on the Arctic environment: in particular on sea-ice movement, sometimes resulting in 'Very Rapid Ice Loss Events' (VRILEs - timescale days to weeks) which present a major challenge to coupled forecasts; and on the baroclinicity (temperature gradients) around the Arctic, influencing subsequent weather systems and forecasts of Arctic climate from weeks out to a season ahead. Our proposed observational experiment will be the first focusing on summer-time Arctic cyclones and taking the measurements required to investigate the influence of sea-ice conditions on their development. New observations are needed comprising of turbulent near-surface fluxes of momentum, heat and moisture measured simultaneously with the sea ice or ocean surface beneath the aircraft track and along cyclone-scale transects. These fluxes dictate the impact of the surface on the development of weather systems. We will operate from Svalbard (Norway) in summer 2021, using the British Antarctic Survey's Twin Otter low-flying aircraft equipped to measure turbulence at flight level and the surface properties through infrared and lidar remote sensing. Our US partners, have designed an observational experiment, called THINICE, looking downwards on Arctic cyclone structure from an aircraft flying above the tropopause (10 km). Our projects are co-designed for summer 2021 so that the observations from the Twin Otter will form a bridge between US airborne and satellite measurements above and the properties of the surface fluxes and sea ice beneath. The project brings together expertise in observations, modelling and theoretical approaches to surface exchange, cyclone dynamics and sea-ice physics. We will use novel theoretically-based approaches to interrogate forecast models as they run and determine the mechanisms through which the surface properties alter cyclone growth. The new surface and turbulence data will be used to improve the parametrization of form drag in models that is central to wind forcing of sea-ice motion as well as decelerating surface winds. These aspects will be explored with state-of-the-art atmosphere and sea-ice dynamics models. Finally, we will close the loop through investigation of the effects of increased surface roughness on Arctic cyclones and their coupled interaction with Arctic temperature gradients. A major legacy of the project will be the unprecedented observations that will enable much needed evaluation and development of environmental forecast models for decades to come.

Biomass burning aerosol (BBA) exerts a considerable impact on climate by impacting regional radiation budgets as it significantly reflects and absorbs sunlight, and its cloud nucleating properties perturb cloud microphysics and hence affect cloud radiative properties, precipitation and cloud lifetime. However, BBA is a complex and poorly understood aerosol species as it consists of a complex cocktail of organic carbon and inorganic compounds mixed with black carbon and hence large uncertainties exist in both the aerosol-radiation-interactions and aerosol-cloud-interactions, uncertainties that limit the ability of our current climate models to accurately reconstruct past climate and predict future climate change. The African continent is the largest global source of BBA (around 50% of global emissions) which is transported offshore over the underlying semi-permanent cloud decks making the SE Atlantic a regional hotspot for BBA concentrations. While global climate models agree that this is a regional hotspot, their results diverge dramatically when attempting to assess aerosol-radiation-interactions and aerosol-cloud-interactions. Hence the area presents a very stringent test for climate models which need to capture not only the aerosol geographic, vertical, absorption and scattering properties, but also the cloud geographic distribution, vertical extent and cloud reflectance properties. Similarly, in order to capture the aerosol-cloud-interactions adequately, the susceptibility of the clouds in background conditions; aerosol activation processes; uncertainty about where and when BBA aerosol is entrained into the marine bundary layer and the impact of such entrainment on the microphysical and radiative properties of the cloud result in a large uncertainty. BBA overlying cloud also causes biases in satellite retrievals of cloud properties which can cause erroneous representation of stratocumulus cloud brightness; this has been shown to cause biases in other areas of the word such as biases in precipitation in Brazil via poorly understood global teleconnection processes. It is timely to address these challenges as both measurement methods and high resolution model capabilities have developed rapidly over the last few years and are now sufficiently advanced that the processes and properties of BBA can be sufficiently constrained. This measurement/high resolution model combination can be used to challenge the representation of aerosol-radiation-interaction and aerosol-cloud-interaction in coarser resolution numerical weather prediction (NWP) and climate models. Previous measurements in the region are limited to the basic measurements made during SAFARI-2000 when the advanced measurements needed for constraining the complex cloud-aerosol-radiation had not been developed and high resolution modelling was in its infancy. We are therefore proposing a major consortium programme, CLARIFY-2016, a consortium of 5 university partners and the UK Met Office, which will deliver a suite of ground and aircraft measurements to measure, understand, evaluate and improve: a) the physical, chemical, optical and radiative properties of BBAs b) the physical properties of stratocumulus clouds c) the representation of aerosol-radiation interactions in weather and climate models d) the representation of aerosol-cloud interactions across a range of model scales. The main field experiment will take place during September 2016, based in Walvis Bay, Namibia. The UK large research aircraft (FAAM) will be used to measure in-situ and remotely sensed aerosol and cloud and properties while advanced radiometers on board the aircraft will measure aerosol and cloud radiative impacts. While the proposal has been written on a stand-alone basis, we are closely collaborating and coordinating with both the NASA ORACLES programme (5 NASA centres, 8 USA universities) and NSF-funded ONFIRE programme (22 USA institutes).

We propose a network to stimulate new international collaboration in measuring and understanding the surface temperatures of Earth. This will involve experts specialising in different types of measurement of surface temperature, who do not usually meet. Our motivation is the need for better understanding of in situ measurements and satellite observations to quantify surface temperature as it changes from day to day, month to month. Knowing about surface temperature variations matters because these affect ecosystems and human life, and the interactions of the surface and the atmosphere. Surface temperature (ST) is also the main indicator of "global warming". Knowledge of ST for >150 years has been derived from in situ meteorological and oceanographic measurements. These have been fundamental to weather forecasting, to environmental sciences, and to detection and attribution of climate change. Thermal remote sensing of ST from space has a ~30 year history, including operational exploitation. Observations of high accuracy and stability come from the 20-year record of Along Track Scanning Radiometers (ATSRs) . ATSR-class capability will shortly become operational in the space segment of Global Monitoring for Environment and Security (GMES), and will continue until at least 2030. The best insight into ST variability and change through the 21st century will come from jointly using in situ and multi-platform satellite observations. There is a clear need and appetite to improve the interaction of scientists across the in-situ/satellite 'divide' and across all domains of Earth's surface. This will accelerate progress in improving the quality of individual observations and the mutual exploitation of different observing systems over a range of applications. Now is a critical time to initiate this research network. First, the network will link closely to a major new initiative to improve quantification of ST from surface meteorological stations (surfacetemperatures.org). Second, there are areas of acute need to improve understanding of ST: e.g., across regions of Africa, where in situ measurements are very sparse; and across the Arctic, where the evolving seasonal sea ice extent challenges the current practices for quantifying ST variability and change. Third, it is timely to share experience between remote sensing communities. All these motivations are present against a backdrop where ST is, in relation to climate change, of current public interest & relevance to policy. This network will increase the international impact of UK science. UK investigators are involved across the full scope of the proposed ST network, and have leading international roles in several areas. The network will ensure UK participation at the highest level across all domains of ST research. In this proposal, key world-class organisations overseas have roles in steering and/or hosting network activities. The network will welcome participation of others not contacted in preparation of this proposal. Permission will be sought from the originators of all data used for case studies to make the data set freely available. The network will be organised around three themes over three years: Year 1. In situ and satellite ST observations: challenges across Earth's domains Year 2: Quantifying surface temperature across Arctic Year 3: Joint exploitation of in situ and satellite surface temperatures in key land regions. The first theme is an inclusive question, designed to bring together research communities and develop a full picture of common research needs and aspirations. The second theme is a pressing research question to which the network will co-ordinate a useful and unique contribution. The third theme is one of long-term interest and importance in the strengthening of the observational foundations for climate change monitoring and diagnosis.

By modifying the amount of solar radiation absorbed at the land surface, bright snow and dark forests have strong influences on weather and climate; either a decrease in snow cover or an increase in forest cover, which shades underlying snow, increases the absorption of radiation and warms the overlying air. Computer models for weather forecasting and climate prediction thus have to take these effects into account by calculating the changing mass of snow on the ground and interactions of radiation with forest canopies. Such models generally have coarse resolutions ranging from kilometres to hundreds of kilometres. Forest cover cannot be expected to be continuous over such large distances; instead, northern landscapes are mosaics of evergreen and deciduous forests, clearings, bogs and lakes. Snow can be removed from open areas by wind, shaded by surrounding vegetation or sublimated from forest canopies without ever reaching the ground, and these processes which influence patterns of snow cover depend on the size of the openings, the structure of the vegetation and weather conditions. Snow itself influences patterns of vegetation cover by supplying water, insulating plants and soil from cold winter temperatures and storing nutrients. The aim of this project is to develop better methods for representing interactions between snow, vegetation and the atmosphere in models that, for practical applications, cannot resolve important scales in the patterns of these interactions. We will gather information on distributions of snow, vegetation and radiation during two field experiments at sites in the arctic: one in Sweden and the other in Finland. These sites have been chosen because they have long records of weather and snow conditions, easy access, good maps of vegetation cover from satellites and aircraft and landscapes ranging from sparse deciduous forests to dense coniferous forests that are typical of much larger areas. Using 28 radiometers, and moving them several times during the course of each experiment, will allow us to measure the highly variable patterns of radiation at the snow surface in forests. Information from the field experiments will be used in developing and testing a range of models. To reach the scales of interest, we will begin with a model that explicitly resolves individual trees and work up through models with progressively coarser resolutions, testing the models at each stage against each other and in comparison with observations. The ultimate objective is a model that will be better able to make use of landscape information in predicting the absorption of radiation at the surface and the accumulation and melt of snow. We will work in close consultation with project partners at climate modelling and forecasting centres to ensure that our activities are directed towards outcomes that will meet their requirements.

OVERCOME consortium include world-leading organisations to develop state-of-the-art research plan that integrates digital innovations in natural hazard and risk predictions in order to develop intervention strategies for strengthening the resilience of vulnerable communities against climate hazards and health impacts. The partners from the UK, Ghana, Malawi, Mozambique, and Zimbabwe will contribute knowledge and skills in climate and meteorology, hydrology and water resources, flood forecasting, droughts, water quality, epidemiology and public health, smart technologies, data science, environmental science, Water, Sanitation and Hygiene (WASH), risk communication, disaster management, social and policy sciences, and socio-economics. The collaboration will combine multidisciplinary knowledge to develop a novel holistic framework to forecast the impact of floods/droughts and associated disease outbreaks. OVERCOME also has strong support from global experts and local major stakeholders. The external partners will steer research direction throughout the project, contribute their complementary knowledge, and engage the team with additional partners through their strong international networking. OVERCOME will organise a kick-off meeting in one African partner's country to (1) brief our research ideas to the key stakeholders in African countries; (2) allow for all parties involved to learn from each other the capacity that each institution can contribute to the OVERCOME consortium; (3) understand the expectations that the stakeholders have on the project; (4) identify the knowledge gaps in research and the extra expertise required within the consortium. Following the kick-off meeting, the lead partners in Ghana, Malawi, Mozambique and Zimbabwe will further reach out to additional partners in their countries to complement the skills within the consortium. Networking and Capacity Building Workshops (NCBWs) will be organised to incorporate local stakeholders for co-designing research methodology and outcomes to ensure that the project outputs will be adopted by stakeholders for real-world practices to deliver long-term impact to communities. Local Stakeholder Engagement Workshops will be held for local stakeholders to review and feedback on the final second stage proposal. The participants will evaluate the objectives and planned tasks from WGs for shaping research topics to benefit most stakeholders and vulnerable communities. The engagement can also examine and guarantee the feasibility of proposed solutions. We will also synergise with other consortia, projects, and professional groups to further strengthen the consortium, enhance the research vision, collect data for the full research, and widen the impact from the project.