Overview

Project Highlights:

  • Work with cutting-edge satellite remote sensing and modelling methods
  • Develop and apply novel approaches for aerosol remote sensing from satellites with high resolution
  • Research into the cutting-edge field of urban aerosol and air quality    

Airborne particles play a critical role in environmental science with major implications for climate and air quality. Particulate matter (aerosols) is one of the most important factors for poor air quality and most of the estimated 4 million excess deaths per year stem from cardiovascular and respiratory diseases caused by particulate matter in the air. However, aerosols are highly complex and variable, especially in cities, due to their diverse sources (vehicle exhaust, industry, fuel-burning etc.) and atmospheric reactions and existing ground-based networks can give us only a very incomplete view on the urban aerosol distribution. For many cities, a new form of observation is required to provide aerosol air quality information to all and would transform our assessment of aerosol distributions and their likely health impacts.

Optical instruments on satellites are an important resource to monitor aerosols from space that can provide us with a wealth of details on aerosols not possible from ground-based observations. However, the spatial resolution of dedicated aerosol sensors is too coarse for cities. Consequently, many key questions on the urban aerosol distribution and their sources are unanswered, limiting our ability so far to make well-informed decisions for improving air quality within cities.

The recently launched Sentinel-2 can fundamentally change our approach to urban aerosols by allowing us to derive aerosol information on an unprecedented scale of tens of meters which is the relevant scale to pinpoint the different aerosol sources (roads, industrial facilities etc.), to diagnose aerosol variations across urban conurbations and to diagnose the impact of transport pathways within a city (street canyons).

In this project, we will make use of the power of the Sentinel-2 satellite to create a novel aerosol dataset with very high spatial resolution and use it to challenge our current understanding of urban aerosols. This studentship offers exciting science opportunities in the important and timely research area of urban air quality which is of large interest to the public and to policy makers. Results will be published in high quality journals and shared with government and local authorities, particularly through contacts in the Department for Environment, Food and Rural Affairs.

Aerosol optical depth observed from the MODIS satellite over the UK at 1 km spatial resolution showing the high variability of aerosol distributions; analysis of Sentinel-2 observations will enable aerosol measurements at a factor 50 to 100 higher spatial resolution (Pope et al., 2018).

Methodology

In this project, we will develop and apply innovative aerosol-specific methods (so-called inversion or retrieval techniques) to the Sentinel-2 satellite to infer aerosol information with fine spatial resolution from space. These methods are cutting-edge because they exploit state-of-the-art mathematical methods ranging from optimisation techniques to artificial intelligence machine learning. Key to analysis of Sentinel-2 will be careful testing of new fast methods to simulate satellite signals and the investigation of methods to separate aerosol signatures from the surface reflectance. Cities provide a fascinating challenge for this work since their structure and topography is complex and access to very good digital maps of cities will be important. The end result of the algorithm development will be a world-leading technique for deriving urban aerosols which will be of major interest to space agencies.

Aerosol data sets for cities will enable new investigations of air quality over a wide range of environmental conditions and will be of considerable interest to local authorities, governments and the public. We will initially focus on UK cities (Leicester, Birmingham, London) where we will carefully characterise and evaluate our new aerosol dataset against ground-based networks and Earth Observation aerosol data from remote sensing, upward-looking sensors such as Aeronet (optical) and Earlinet (lidar). These UK cities have the advantage of well-founded public and research aerosol networks at ground level and years of aerosol-related research. Hence the new data sets of the project can be assessed with confidence and also used to identify new research through collaborations. We will use the dataset to investigate the aerosol distribution over cities, especially for those with previously much less well-known transport and industrial sources, and to critically assess current air quality model data.

Finally, we will apply the retrieval method to major megacities across the world. Development in Asian cities has expanded rapidly in a changing environment which includes increased dust and aerosol particles from agriculture-related fires. Cities in China have increasingly suffered from the highest air pollution problems but in very recent times Delhi in India, for example, has suffered severe problems. Hence the project has the potential to make a difference in some critical urban conurbations where information can be sparse on sources and transport of aerosol particles.

Training and Skills

The students will be part of the Leicester Earth Observations Science research group which provides an exciting cross-disciplinary environment. The student will obtain a wide range of skills and expertise in satellite remote sensing, carbon cycle and wider environmental science. Specific training will be provided by the supervisory team and partners with additional training provided via summer school (e.g. ESA summer school), workshops and University training (e.g. computing). The student will also benefit from the National Centre for Earth Observation (NCEO) which provides numerous training opportunities from data visualization to presentation skills. NCEO also provides ample opportunities to interact with researchers and PhD students

Timeline

Year 1: Training in satellite remote sensing methods and aerosol retrieval methods. Evaluate different aerosol datasets for cities (UK aerosol models, EO networks such as Aeronet, ground-based public and research networks) and setup initial retrieval method. Attend summer school.

Year 2: Apply retrieval method to Sentinel2 and generate dataset for UK cities. Evaluate the aerosol data from Sentinel2 and comparison to ground-based aerosol data and air quality model data. Presentation at NCEO national EO conference and an international conference.

Year 3: Extend the Sentinel2 aerosol retrieval to cities in Asia, particularly India and China. Presentation at international conference.

Partners and collaboration (including CASE)

In the studentship, we will work with partners from the National Centre of Earth Observation NCEO.

Further Details

It is advised that you contact the supervisors Prof. John Remedios (jjr8@le.ac.k) and Prof. Hartmut Boesch (Hartmut.boesch@le.ac.uk) before applying

For more details about the EOS group, please see https://www2.le.ac.uk/departments/physics/research/eos