First Results from the Relocated and Enhanced Purple Crow Lidar

The University of Western Ontario's Purple Crow Lidar (PCL) has been in near continuous operation since 1993 and routinely measures temperature from 10 km to above 100 km, water vapor mixing ratio in the troposphere and stratosphere, as well as aerosol products. The PCL was recently relocated to a new custom-built, environmentally friendly facility at Western's Environmental Research Station located 9 km north of the campus. The PCL move allowed the opportunity for many new and exciting instrumentation upgrades and improvements. Our new transmitter, a Litron Nd:YAG laser, produces 1000 mJ/pulse at 532 nm with a 30 Hz repetition rate (i.e. 30 W). This new laser increases our transmitter power by 2.5 times compared to our previous laser and boosts the PCL's power-aperture product to 160 W/m². We have also upgraded the counting electronics to improve the vertical height resolution of our Rayleigh temperature from 24 m to 7.5 m and our water vapour, vibrational Raman temperature, and aerosol measurements from 250 m to 24 m. As well, the system is now capable of automatic alignment during operations. The water vapor measurements have been further improved by the addition of a white light calibration source. We are in the process of upgrading the system for more direct aerosol measurements by including a low altitude aerosol channel using a small co-aligned telescope. The enhanced system will have two major impacts on upper mesosphere/lower thermosphere science. First, our new laser will allow our temperature measurements to gain another 10 km in altitude, pushing them at times above 110 km. Second, due to the new inversion method developed by Khanna (2011), an assumption of a seed pressure at the top of the atmosphere will no longer be required, so any systematic retrieval uncertainties will be less than the measurement statistical uncertainty in the lower thermosphere. With the seeding of the temperature profiles now done at the lowest heights (i.e. stratosphere), the measurements may now allow the retrieval of molecular oxygen and nitrogen profiles in the mesosphere and lower thermosphere (Mwangi et al., 2001; Argall, 2007). We will present initial results from our enhanced system, highlighting the improvement of our measurements in the mesosphere and lower thermosphere.