Overview

Project Highlights:

  • Learning how to do hands-on work with lasers and optics
  • Understanding air pollution sources and atmospheric transport
  • Developing and deploying new technology with real-world applications to human health and climate science

Aerosols are solid and/or liquid particles suspended in the atmosphere, spanning in size from a few nanometers to tens of micrometers. Common aerosol types include dust, smoke, sea salt, and particulate vehicle exhaust.  While there is growing understanding of the impacts of different aerosols, which range from being hazardous to human health to driving weather and climate processes, there is much to be learned about the relative spatial and temporal distributions of different aerosol types throughout the atmosphere. As they are highly variable in their physical and chemical properties due to their wide range of natural and human-driven sources, differences in size, shape and composition can be detected by the different ways aerosols interact with light.

Light detection and ranging (lidar) techniques are in use for example in the ACTRIS EARLINET [1] network of advanced laser measurement observatories to gather information about aerosols in the atmosphere.  Backscatter and exctinction measurements at different wavelenghts and polarizations of light are used along with passive measurements and chemical transport models to assess type and amount of aerosol.  However the number of these expensive stations is limited and there is a need for development of smaller, lower cost instruments to increase the measurement coverage.  Figure 1 gives an example of what can be measured with one low cost laser channel.  This includes verticle structure of aerosol layers, and identification of times and heights of enhanced aerosol plumes.  However, from this system the type of aerosol present cannot be assessed without the adition of external information.

This project will utilize low cost laser and detector technology at a variety of wavelengths and novel optical design techniques to develop a new laser-based aerosol remote sensing instrument.  This new instrument will enable broader coverage of the atmosphere anda  range of new applciations thanks to its low cost and mass.  To optimize the design, performance will be simulated for a variety of conditions.  Later, the performance of the new instrument will be evaluated through field campaigns in Greece or Italy.

Single wavelength 905nm lidar backscatter measurements over Athens Greece, 17 June, 2014, using a prototype lidar optical design by Vande Hey [2].  More wavelenths and polarization measurements are needed to discriminate among aerosol types.

Methodology

Based on low cost laser wavelengths, the student will model the interaction of their light with aerosols of different types, to assess signal to noise ratio requirements and to specify which aerosol types could be identified with a prototype design.  The student will analyse existing data from EARLINET lidars to establish a baseline data processing approach.

Preferred lasers and detectors will be selected, and an optical design will be developed and tested.  When the prototype is fully operational, the student will take the instrument on a field campaign in Europe to compare with instruments at an ACTRIS site.

Data analysis will be carried out, and the capabilities and uncertainties of the prototype will be assessed through comparison with data from higher specification instrumentation.  Impact of observations from a network of such instruments on air pollution modelling for human health, and improved understanding of aerosol roles in climate will be evaluated.

Training and Skills

CENTA students are required to complete 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to CENTA research themes. 

The student will begin by developing a foundation in the physics of light interaction with different sizes, shapes, and compositions of small particles under guidance from supervisors as well as specialist training.  Training on use of an aerosol optical scattering model will also be provided during this time.  A course in optical design and supporting mentorship will also be available.  A secondment at a European ACTRIS partner, for example in Italy or Greece is anticipated during the third year of the program, for further training and a field campaign.

Timeline

Year 1: Receive training in aerosol optical and physical properties.  Apply this to existing aerosol lidar data from EARLINET.  Develop an understanding of aerosol light scattering of available low-cost laser wavelengths, and predict which aerosols could be identified by a new low-cost system. 

Year 2: Receive optical design training.  Develop a prototype optical design for a low-cost aerosol lidar, and build a test platform, with engineering support.  Carry out preliminary testing and iteration in Leicester.  

Year 3: Travel to an ACTRIS EARLINET site in Greece or Italy to deploy the new sensor alongside other instruments.  Receive training in data analysis during a secondment to this facility.  Assess the performance and uncertainties of the sensor against reference instruments.  Consider applications for a network of these sensors in air quality and human health, and climate science.

Partners and collaboration (including CASE)

This PhD studentship will be hosted in the Department of Physics and Astronomy at the University of Leicester, supervised by Dr. Joshua Vande Hey and Dr. Hartmut Boesch.

Dr Vande Hey is NERC KE Fellow in Aerosols and Health. His research ranges from optical sensor development with industry to use of environmental data for health applications.

Dr Boesch heads the Earth Observation Science Group. His research focuses on improving our understanding of climate through remote sensing, collaborating with NASA and ESA.

This project will engage with the European ACTRIS network (Aerosol and Trace Gas Research Infrastructure), and there is strong potential for industrial collaboration.

Further Details

For further information please contact Dr. Joshua Vande Hey, jvh7@le.ac.uk .  Learn more about Dr. Vande Hey’s work here:

http://www2.le.ac.uk/departments/physics/research/eos/joshua-vande-hey

And Dr. Boesch’s work here:

http://www2.le.ac.uk/departments/physics/research/eos/hartmut-boesch