Remote Sensing for Air Quality Impact Assessment

Poor air quality is a threat to human health and ecosystems across many parts of the developed World (especially in Europe and North America) and is rapidly worsening in parts of the developing World (especially in Asia and parts of Africa). There is a large focus on understanding air pollution impacts on human health and how pollution concentrations (especially ozone and particulate matter or aerosol) contribute to premature deaths and increases in cardiovascular disease. However, air pollution also affects ecosystems, here impacts vary from effects on yield, biomass and biodiversity losses which can lead to reductions in crop and timber yields and changes in species composition of ecosystems. Impacts on vegetation biomass will also affect carbon sequestration (less carbon being held in living biomass leading to more carbon dioxide in the atmosphere) which will enhance climate change. Air pollution has also been found to affect the control that plants have over gas exchange resulting in increased transpiration which can in turn alter stream flow and hydrology. Even though these effects threaten food security, natural resources & biodiversity and the regulation of supporting biophysical systems our understanding of air pollution effects on ecosystems is far less advanced compared to that for human health, especially when considered at the global scale.

This project seeks to redress that balance using novel approaches that will bring together state of the art advances in the interpretation of satellite data targeted towards helping evaluate global air quality models and improve their ability to make future predictions of air pollution impacts on ecosystems. The project will focus efforts by developing a data and modelling framework that provides a means of integrating different components (chemistry transport models, pollution impact models, satellite data of pollutant concentrations, land cover characteristics, surface monitoring data) that, when brought together, will advance our knowledge of air pollution impacts to vegetation. The project will target specific aspects of this integration to reduce key uncertainties in air pollution impact assessment and allow future advancements in both remote sensing and air quality disciplines to be more easily integrated in the future. These are i. incorporation of seasonal cycles of canopy architecture derived from satellite data into chemistry transport models; ii. use of satellite derived distributions of ozone, aerosol, photosynthetically active radiation and fluorescence to evaluate chemistry transport model outputs and; iii. inclusion of methods to simulate photosynthesis and fluorescence into chemistry transport models so that the combined action of aerosol and ozone on photosynthesis (and subsequent vegetation damage) can be more readily compared with satellite data observations.

Finally, the project will culminate in an end user workshop to raise awareness of these new developments and their potential application to the broader scientific community concerned with understanding the influence of air pollution on atmospheric and terrestrial biosphere exchange processes. The project will also benefit a range of stakeholders with interest in air quality including i. national government through contribution to improving national scale modelling of air pollution; ii. European bodies involved in the UNECEs Convention on Long Range Transboundary Air Pollution who require estimates of pollution concentration and associated impacts to human health and vegetation across Europe; and iii. organisations such as UNEP active at the global level tasked with developing policies that can most effectively mitigate the most damaging effects of air pollution. Finally, the project will also benefit the Earth System Modelling community who are currently developing methods to improve our understanding of the effect of air pollution on atmosphere-biosphere exchange.

The following stakeholders and user groups will be likely to benefit from this research, for each a brief summary of how they will benefit is also provided.

At the national level the project will feed into the UK Defra (Air Quality Division) and DECC (via PI Emberson). The new satellite techniques developed to observe surface ozone concentrations and column aerosol concentrations above the UK and Europe will help in evaluation of the atmospheric chemistry models that Defra uses for conducting its air quality assessments.

At the European scale, the project team will work closely with the UNECE Long-Range Transboundary Air Pollution (LRTAP) and in particular, EMEP (the European Monitoring and Evaluation Programme), the Vegetation and Hemispheric Transport of Air Pollution (HTAP) programmes, as well as the Working Group on Effects (via PI Emberson), this latter group will also provide links to the European Commission. EMEP are tasked with monitoring and modelling of air pollution and its impacts across Europe. EMEPs atmospheric chemistry modelling will benefit from the improvements to the descriptions of European land cover (i.e. the characterisation of Leaf Area Index) which is crucial for current air pollution deposition and impact estimates. The UNECE Vegetation Programme will benefit from the development of techniques to observe and simulate fluorescence. This group have been interested in understanding air pollution impacts to vegetation for almost 20 years. The potential to observe changes in a key product of photosynthesis and relate this to air pollution concentrations opens up an exciting new opportunity to observe plant stress over continua of space and time which have not been possible to date. The inclusion of the simulation of fluorescence in the modelling conducted within this project also provides an opportunity to relate this stress directly to pollutant loads and deposition. The HTAP programme is interested in how air pollution and its precursors circulate around the globe. This programme of work has again been extremely reliant on site-specific monitoring networks (of limited density in parts of the developing World) and global modelling efforts. Full global coverage of both ozone and aerosol pollution fields (both these pollutants are an important focus of HTAP) will provide additional and extremely important evaluation data for HTAP modelling efforts. This will benefits HTAPs attempts to understand the role that pollution sourced from 'foreign' regions will have on domestic impacts such as human health and reduced ecosystem productivity.

At this global scale, the project will also connect strongly with existing academic and institutional initiatives around the world focussing on collecting air pollution data from concentration and flux monitoring networks around the World such as those hosted by the World Meteorological Organisation (https://www.wmo.int/pages/index_en.html). The project will also connect with the UNEP air quality and climate change programmes, especially those involved in understanding the potential for reducing short-lived climate pollutants (ozone and aerosol) such as the Climate Clean Air Coalition (http://www.unep.org/ccac/). These programmes are currently developing National Action Plans for a number of countries around the globe to develop appropriate pollution emission reduction policies (suitable for the countries particular social, economic and political conditions). The development of methods to monitor pollutant concentrations using satellites will provide a real time means of assessing the effectiveness of the implementation of policies to curb air pollution emissions. The development of air quality modelling techniques will also help develop scenario modelling to understand the effectiveness of such policies in the near future (i.e. in the next 10 to 20 years).