The continuous measuring of the vertical profile of water vapor in the boundary layer using a commercially available differential absorption lidar (DIAL) has only recently been made possible. Since September 2018, a new pre-production version of the Vaisala DIAL system has operated at the Iqaluit supersite (63.74°N, 68.51°W), commissioned by Environment and Climate Change Canada (ECCC) as part of the Canadian Arctic Weather Science project. This study presents its evaluation during the extremely dry conditions experienced in the Arctic by comparing it with coincident radiosonde and Raman lidar observations. Comparisons over a one year period were strongly correlated (r > 0.8 at almost all heights) and exhibited an average bias of +0.13 ± 0.01 g/kg (DIAL-sonde) and +0.18 ± 0.02 g/kg (DIAL-Raman). Larger differences exhibiting distinct artifacts were found between 250 and 400 m above ground level (AGL). The DIAL’s observations were also used to conduct a verification case study of operational numerical weather prediction (NWP) models during the World Meteorological Organization’s Year of Polar Prediction. Comparisons to ECCC’s global environmental multiscale model (GEM-2.5 km and GEM-10 km) indicate good agreement with an average bias < 0.16 g/kg for the higher-resolution (GEM-2.5 km) models. All models performed significantly better during the winter than the summer, likely due to the winter’s lower water vapor concentrations and decreased variability. This study provides evidence in favor of using high temporal resolution lidar water vapor profile measurements to complement radiosonde observations and for NWP model verification and process studies.

LIDAR technology has been rapidly advancing over the past several decades. It can be used to measure a variety of atmospheric constituents at very high temporal and spatial resolutions. While the number of LIDARs continues to increase worldwide, there is generally a dependency on an operator, particularly for high-powered LIDAR systems. Environment and Climate Change Canada (ECCC) has recently developed a fully autonomous, mobile LIDAR system called AMOLITE (Autonomous Mobile Ozone LIDAR Instrument for Tropospheric Experiments) to simultaneously measure the vertical profile of tropospheric ozone, aerosol and water vapor (night time only) from near ground to altitudes reaching ten to fifteen kilometers. This current system uses a dual laser, dual LIDAR design housed in a single climate-controlled trailer. Ozone profiles are measured by the DIfferential Absorption LIDAR (DIAL) technique using a single 1 m Raman cell filled with CO₂. The DIAL wavelengths of 287 nm and 299 nm are generated as the second and third Stokes lines resulting from stimulated Raman scattering of the cell pumped using the fourth harmonic of a Nd:YAG laser (266 nm). The aerosol LIDAR transmits three wavelengths simultaneously (355 nm, 532 nm and 1064 nm) employing a detector designed to measure the three backscatter channels, two nitrogen Raman channels (387 nm and 607 nm), and one cross-polarization channel at 355 nm. In addition, we have added a water vapor channel arising from the Raman-shifted 355 nm output (407 nm) to provide nighttime water vapor profiles. AMOLITE participated in a validation experiment alongside four other ozone DIAL systems before being deployed to the ECCC Oski-ôtin ground site in the Alberta Oil Sands region in November 2016. Ozone was found to increase throughout the troposphere by as much as a factor of 2 from stratospheric intrusions. A biomass burning event that impacted the region over an eight-day period produced LIDAR ratios of 35 to 65 sr at 355 nm and 40 to 100 sr at 532. Over the same period the Angstrom exponent decreased from 1.56 ± 0.2 to 1.35 ± 0.2 between the 2 to 4 km smoke region. The advantage of nearly continuous measurements obtained over a 12-month period will be presented, highlighting the synergistic advantage of AMOLITE’s tri-LIDAR design.