Understanding volcanic emissions is important for several reasons over several spatial scales. These are (i) they can be hazardous to health; (ii) they can affect the local environment; (iii) they contain information pertaining to the volcanic system of origin; (iv) they can perturb local and, if the eruption is large enough, global climate systems, and; (v) they can be hazardous to aircraft. Typically, points (iii), (iv) and (v) drive my research, which involves inversion of remotely sensed data to retrieve physical parameters of volcanic plumes and clouds, from several regions of the electromagnetic spectrum, using both ground- and satellite-based remote sensing techniques. These include the ultraviolet and thermal infrared for gas spectroscopy, and visible, near infrared (Sun-photometers) and thermal infrared for aerosol retrievals. My current research includes investigation of SO2 and sulphate retrievals, generation of an aerosol forward model, atmospheric correction of ash retrievals; spectrally independent calibration of SO2 retrievals using TOMS, ASTER, MODIS and AIRS, and the use of the ASTER, MODIS and AIRS in the retrieval of volcanic SO2, sulphate, and silicate ash burdens.
RESEARCH QUESTIONS I WILL CONTINUE TO ADDRESS OVER THE NEXT FIVE YEARS:
(i) How do gas emission rates vary on short (< one hour) timescales and can changes immediately before explosions be quantified? I have had three Ph.D students (Yvonne Branan, Marika Dalton and Peter Holland) and two MSc students (Jean-François Smekens and Tom Bouquet) working on comparing high temporal resolution DOAS and UV camera data and comparing it to geophysical data to elucidate subsurface processes. Tanya Gray (PhD student) continues to focus on this problem.
(ii) How can current satellite-based retrievals be improved to deal with the spectral interaction of multiple species? Single-species algorithms are currently applied to AVHRR, GOES, and MODIS data in order to mitigate aviation hazard and quantify volcanic emissions. I have had four PhD students (Emily McCarthy, Lorna Henney, Courtney Kearney and Helen Thomas) developing multi-species retrievals through a NASA algorithm development grant.
(iii) What are the fates of volcanogenic species and how can we best synergise transport models and remote sensing data? I have had three PhD students (Lizzette Rodriguez, Alvaro Amigo and Alex Matiella-Novak) and three MSc students (Emma Johnston, Dan Skinner and Prajacka Patil) working at the interface of spatio-temporal modelling and remote sensing. They use a variety of validation techniques (including DOAS and Sun-photometry), satellite imagery and GIS tools to attempt to ground-truth chemical, transport and depositional models.
(iv) How can aviation hazard be more effectively mitigated? Specifically, how can the effects of water vapour variation upon the split-window retrieval be accounted for? I intend to develop and empirical atmospheric correction for ash maps based upon radiative transfer code to correct for water vapour in temperature difference maps. Shona Mackie (a post-doctoral researcher) continues and augments the work undertaken by PhD (Helen Thomas, Emily McCarthy, Alex Matiella, Lorna Henney) and MSc students (Dan Williams and Matt Donovan).
(v) How can we improve volcanic gas emissions studies through the application of new technologies? Through development of real-time SO2 monitoring using UV sensitive focal-plane array cameras, I intend to provide volcano observatories with real-time images of SO2 gas plumes to advance monitoring using change in gas emission rates. There has been a Ph.D student (Peter Holland) and three MSc students (Jean François Smekens, Ryan Townley and Tom Bouquet) working on this problem.
(vi) How does mineral dust impact the radiative balance of the atmosphere? I have had two post-doctoral researchers (Adam Durant and Daniel Peters) and an MSc students (Tom Steensen) working on various aspects of this problem: radiative transfer of mineral dust through sensitivity analysis, and global mapping.
(vii) What can we learn about solar radiation management from large explosive eruptions? Through the RCUK-funded project 'Stratospheric Particle Injection for Climate Engineering' I am investigating the ecological, chemical and radaitive effect of injecting reflective particles into the lower stratosphere. There are three post-doctoral researchers (Pru Foster, Dan Peters and Minjing Tang) addressing this problem.
(viii) How can we get data to decision makers in a timely manner? The group is involved in a multi-centre proposal to deliver science products to volcano observatories in near real-time. This is the ASTER Urgent Request Protocol (NASA) continuation project and is part of Helen Thomas's remit.