Vacancies

Supervisor: Mervyn Lynch

Co-supervisor: Helen Chedzey

The two extremes of cloud cover are totally clear skies or total cloud cover. With ~ 70 % of the Earth cloud-covered at any time, partial cloud cover is the most likely condition. The global modulating effect of clouds on climate is a key controller of global warming with, in principle, a 4% change in cloud cover able to reverse the current impact of CO2 warming. The temperature of the land surface due to incoming solar radiation is reduced the higher the surface reflectivity in the visible spectral region. However, the ability of the land surface to cool is enhanced if the emissivity of the surface is high in the infrared region of the spectrum. The interplay of these two physical processes is important in understanding global warming and climate change but also in phenomena such as the urban heat island effect. For example, greening suburbs increases their overall infrared emissivity. The project will involve field campaigns using infrared sensors to explore the subtleties of these thermodynamic processes for different surfaces and environmental conditions.

Supervisor: Mervyn Lynch

Co-supervisor: Helen Chedzey

Optical communication links (eg using encoded laser beams) provide much higher bandwidths than are possible to achieve with radio communication links such as wi-fi. For high bandwidth duplex optical communications between the surface-based facilities and orbiting satellites, cloud cover and atmospheric turbulence are serious limiting operating factor frequently requiring use of multiple well-spatially separated ground stations. However, operators of these systems are able to function when thin clouds are present. Deciding in advance as to whether a cloud is thin or thick is more challenging, particularly at night time. The approach is to employ ground-based infrared remote sensing to establish the relationship between a cloud’s optical transmittance (optical depth) and its infrared emissivity since the latter can be measured. The project will use infrared sensors to investigate water and ice clouds and validate their properties. The project is linked to the establishment of ground-based infrastructure for an Australia-Japan collaborative Regional Engagement Fund initiative.

Supervisor: David Antoine

The RSSRG has deployed a profiling mooring off Rottnest Island, Perth. This new equipment collects vertical profiles of optical and biological properties of waters at that site. The data set allows deriving the water reflectance, which can then be compared to the same parameter as delivered by satellite remote sensing instruments, in particular the “Ocean and Land Colour Imager” (OLCI) launched in 2016 by the European Space Agency (ESA) on board the Sentinel-3 satellite. The work will consist in processing the profiling mooring data set, sourcing the corresponding data from the satellite observations, and evaluating how well they match. The results will be communicated to the “Sentinel validation team”, which is an international group of scientists working on the global evaluation of the quality of OLCI products, under ESA leadership.

Supervisor: David Antoine

Physical and biological properties of oceanic waters off Western Australia (WA) are largely influenced by the Leeuwin Current (LC), which is the major southward flow of warm, low-salinity tropical waters along WA coasts. It varies on inter-annual to decadal time scales, in particular under influence of the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). Mesoscale eddies in the Leeuwin Current have profound influence on temperature and chlorophyll distributions in the region. For example, the warm-core eddies that spin off from the LC have a significant effect on the level of productivity in the mid-west region. Here we propose to study the spatial and temporal scales of variation of phytoplankton off WA through the use of NASA and ESA satellite ocean colour remote sensing products. Archives of such products date back to 1998 and, therefore, allow studying seasonal, inter-annual and decadal changes.

Supervisor: David Antoine

Phytoplankton are the microscopic unicellular algae living in the top layers of the ocean, where light and nutrients are available for these organisms to develop through the photosynthetic process. They are the basis of the marine food web and are therefore a key component of marine ecosystems. The RSSRG has deployed a profiling mooring off Rottnest Island, Perth, which collects vertical profiles of water optical and biological properties in view of getting better insight about time changes of phytoplankton and their distribution within the water column. Among these properties are the phytoplankton chlorophyll fluorescence, which is a proxy for phytoplankton biomass, the particle optical backscattering coefficient, which is a proxy for the amount and type of particulate matter in the water, and the absorption coefficient, which provides additional information on the influence of particulate matter (in particular phytoplankton) on the water optical properties. The work we propose here would combine these different parameters to provide insights into phytoplankton dynamics on that site.

Supervisor: David Antoine

In May-June 2019, the RSSRG participated to a 1-month research voyage on R/V Investigator (see links below), exploring waters of the Eastern Indian Ocean (EIO) off WA, from 40°S to 10S along the 110°E longitude. During this voyage we have sampled optical and phytoplankton properties of the upper (0-200m) water column, and we have also measured the underwater light field and the light (the “radiance”) leaving the surface ocean. The latter is the one that then travels through the atmosphere and is recorded by satellite instruments orbiting around the Earth. Here we propose to work on comparing various ways of getting the “water-leaving radiance” either from extrapolating measurements taken by instruments that are deployed below the surface or from instruments that are installed on the ship and measure the water-leaving radiance from above the surface.