Cloud fraction statistics derived from 34-months of high spectral resolution lidar data acquired at Eureka, Canada.

The Canadian Network for the Detection of Atmospheric Change (CANDAC) and the NOAA Study of Environmental Arctic Change (SEARCH) have installed instrumentation at Eureka(80 deg N, 86 deg W) in the Nunavut territory of Northern Canada. These instruments include the University of Wisconsin Arctic High Spectral Resolution Lidar(AHSRL) and the NOAA 8.6 mm wavelength cloud radar (MMCR). Both instruments were installed in Sept 2005. This paper presents a record of cloud cover, cloud altitude and cloud phase derived from 34-months lidar data. It also presents comparisons between lidar, radar, and convention meteorological observations of cloudiness. It is shown that optically thin clouds are frequently observed. As a result, the observed fractional cloud cover depends strongly on the optical depth threshold used to define the presence of cloud.