Water vapour lidar system

Water vapour is a trace gas that plays a crucial role in the atmosphere. It is the dominant greenhouse gas, so that a detailed knowledge of the variation (temporal and geographical) of concentration is important for climate studies. Measuring and modelling water vapour concentrations with height and time are important aspects of weather forecasting. However, water vapour shows rapid variability both spatially and temporally. Near real-time measurements of the variability would help greatly with weather forecasting, as well as having significant impacts on understanding processes as diverse as the initiation of convection and fog formation.

This project is a joint initiative of the Optics and Laser Physics and Atmospheric Physics groups at the University of Adelaide. It grew out of the desire to understand the role that water vapour plays in determining the strength of VHF (~50 MHz) atmospheric radar echoes from the lower troposphere.

We are taking two approaches: a dual wavelength system known as DIAL (differential absorption lidar) and Raman lidar. For DIAL two laser wavelengths are transmitted, and the light back-scattered by aerosols is detected. The wavelengths are chosen so that one is absorbed by intervening water vapour and the other is not. From the returns at these two wavelengths we can infer the vater vapour concentration in the atmosphere.

In Raman lidar we detect the light that has been shifted in wavelength by the molecule of interest, and from its intensity we infer the concentration.

The DIAL now works, but we need to extend its range and ruggedize it so that it can be taken into the field. The Raman system is currently under construction.

Student Projects available!! Contact A/Prof Murray Hamilton or Prof. Bob Vincent.

Personnel

A/Prof Murray Hamilton
Prof Bob Vincent (Atmospheric Group)
Ms Sheeja Surendran Nair Kumari Thankam