Western University Physics adn AstronomyWestern Science

Robert Sica, Professor, and Department Chair

Robert Sica

Contact Information

Office: PAB 256
Tel: (519) 661-2111 x83521
E-mail: pachair [at] uwo [dot] ca

Research Blog
Purple Crow Lidar

Research Areas

Space and Atmospheric Science

Research Interests

My research mainly concerns measurements of temperature and composition in the middle atmosphere. Specific areas of expertise include:

  • dynamics of the middle and upper atmosphere
  • effects of gravity waves on the atmosphere
  • novel signal processing techniques to investigate waves
  • effects of aurorae on the upper atmosphere
  • laser remote sensing of the atmosphere
  • application of liquid mirrors for lidar receivers.

My primary research tool is the Purple Crow Lidar (PCL; http://pcl.physics.uwo.ca), which measures temperature and composition of the Earth's atmosphere from the surface to 110 km altitude. The PCL is able to make these measurements at unprecedented accuracy by using a 2.65 m diameter liquid mirror telescope. The liquid mirror is a Canadian technology which allows large mirrors to be built at a fraction of the cost of traditional glass mirrors. Our expertise in these mirrors is due to our longstanding collaboration with Professor E. Borra’s group at the Université Laval, world leaders in this technology. 

The long-term objectives of this research program are to search for atmospheric change and to help improve weather forecasting. Temperature change in the middle atmosphere is not directly affected by land, cities or oceans like surface temperature measurements, and in this region of the atmosphere surface heating corresponds to cooling (due to increased radiation of heat from CO2). The PCL measures water vapor composition change will be measured at both middle and high latitudes. In the middle atmosphere water vapor is an important part of the ozone cycle. We also measure layers of smoke particles in the upper troposphere and stratosphere (> 10 km altitude) associated with distant forest fires, injected into the stratosphere via a process called pyroconvection. The smoke particles can travel great distances, and affect both ozone concentration and temperature. With the number and severity of forest fires increasing, forest fires play a more complex role in global warming than anticipated, and we are trying to understand these effects.

The PCL also measures disturbances in the air density similar to waves on the surface of a lake called gravity waves. These waves break like ocean waves on a beach, primarily at altitudes above 50 km. Remarkably, even waves that break 100 km above the surface play an important role in determining the behaviour of weather systems which affect us on the surface. Furthermore, the gravity waves alter composition and thus affect ozone.
I am currently the Instrument Mentor for a stratospheric ozone lidar located at the Polar Environment Research Laboratory (PEARL) in Eureka, Nunavut. This site is only 1100 km from the North Pole and is part of the Canadian Network for the Detection of Atmospheric Change (CANDAC, http://www.candac.ca). Some of my students visit PEARL in the middle of the Arctic Night to make measurements. Maybe you want to join them!


  1. Sica, R. J., and A. Haefele (2016), "Retrieval of water vapor mixing ratio from a multiple channel Raman-scatter lidar using an optimal estimation method", Appl. Opt. 55, 763-777 (submitted 2016).
  2. Sica, R. J., and A. Haefele (2015), "Retrieval of temperature from a multiple-channel Rayleigh-scatter lidar using an optimal estimation method", Appl. Opt., 54(8), 1872–1889, doi:10.1364/AO.54.001872.
  3. Sica, R. (1999), "Measurements of the effects of gravity waves is the middle atmosphere using parametric models of density fluctuations. Part II: Energy dissipation and eddy diffusion", J Atmos Sci, 56(10), 1330–1343.
  4. Sica, R. J., S. Sargoytchev, P. S. Argall, E. F. Borra, L. Girard, C. T. Sparrow, and S. Flatt (1995), "Lidar Measurements Taken with a Large-Aperture Liquid Mirror .1. Rayleigh-Scatter System", Appl. Opt., 34(30), 6925–6936.
  5. Sica, R., G. Hernandez, G. Romick, M. Rees, and R. Roble (1986), "Auroral-Zone Thermospheric Dynamics .2. Individual Nights", J Geophys Res-Space, 91(A12), 13593–13611.

[Complete Publications Listing]


I have developed courses at The University of Western Ontario in both atmospheric sciences (e.g. Physics 2070 for non-scientists and Physics 2700 for physics students) and the science of the sporting environment (Physics 2065). The sports course, intended for non-science students, is unique as it focusses on the effect of the land, air and water on an athlete’s performance using examples from activities including cycling, skating, athletics and swimming. A text for the course is currently in preparation.


  • 2003    The University of Western Ontario's Florence Bucke Science Prize
  • 1995    Editor's Citation for Excellence in Refereeing for Geophysical Research Letters (American Geophysical Union)

Professional Activities

  • Councillor-at-Large for the Canadian Meteorological and Oceanographic Society (CMOS)
  • Theme Leader, The Polar Night, for the NSERC Climate Change and Atmospheric Research project Probing the Atmosphere of the High Arctic (PAHA)
  • Member,  International Institute for Space Sciences' International Team on Network for Detection of Atmospheric Climate Change Lidar Algorithms