Three-channel single-wavelength lidar depolarization calibration
- 1Department of Physics and Astronomy, The University of Western Ontario, 1151 Richmond St., London, ON, N6A 3K7, Canada
- 2Department of Physics and Atmospheric Science, Dalhousie University, 6310 Coburg Rd., P.O. Box 15000, Halifax, NS, B3H 4R2, Canada
- acurrently at: Facility for Airborne Atmospheric Measurements, Building 146, Cranfield University, Cranfield, MK43 0AL, UK
Abstract. Linear depolarization measurement capabilities were added to the CANDAC Rayleigh–Mie–Raman lidar (CRL) at Eureka, Nunavut, in the Canadian High Arctic in 2010. This upgrade enables measurements of the phases (liquid versus ice) of cold and mixed-phase clouds throughout the year, including during polar night. Depolarization measurements were calibrated according to existing methods using parallel- and perpendicular-polarized profiles as discussed in ). We present a new technique that uses the polarization-independent Rayleigh elastic channel in combination with one of the new polarization-dependent channels, and we show that for a lidar with low signal in one of the polarization-dependent channels this method is superior to the traditional method. The optimal procedure for CRL is to determine the depolarization parameter using the traditional method at low resolution (from parallel and perpendicular signals) and then to use this value to calibrate the high-resolution new measurements (from parallel and polarization-independent Rayleigh elastic signals). Due to its use of two high-signal-rate channels, the new method has lower statistical uncertainty and thus gives depolarization parameter values at higher spatial–temporal resolution by up to a factor of 20 for CRL. This method is easily adaptable to other lidar systems which are considering adding depolarization capability to existing hardware.