Abstract
Doppler light detection and ranging (lidar) wind profilers have proven their capability to measure vertical wind profiles with an accuracy comparable to anemometers and radiosondes. However, most of these comparisons were performed over short time periods or at mid-latitudes. This study presents a multi-year assessment of the accuracy of Doppler lidar wind-profile measurements in the Arctic by comparing them with coincident radiosonde observations, and excellent agreement was observed. The suitability of the Doppler lidar for verification case studies of operational numerical weather prediction (NWP) models during the World Meteorological Organization’s Year of Polar Prediction is also demonstrated, by using Environment and Climate Change Canada’s (ECCC) global environmental multiscale model (GEM-2.5 km and GEM-10 km). Since 2016, identical scanning Doppler lidars were deployed at two supersites commissioned by ECCC as part of the Canadian Arctic Weather Science project. The supersites are located in Iqaluit (64°N, 69°W) and Whitehorse (61°N, 135°W) with a third Halo Doppler lidar located in Squamish (50°N, 123°W). Two lidar wind-profile measurement methodologies were investigated; the velocity-azimuth display method exhibited a smaller average bias (−0.27 ± 0.02 m/s) than the Doppler beam-swinging method (–0.46 ± 0.02 m/s) compared to the sonde. Comparisons to ECCC’s NWP models indicate good agreement, more so during the summer months, with an average bias < 0.71 m/s for the higher-resolution (GEM-2.5 km) ECCC models at Iqaluit. Larger biases were found in the mountainous terrain of Whitehorse and Squamish, likely due to difficulties in the model’s ability to resolve the topography. This provides evidence in favor of using high temporal resolution lidar wind-profile measurements to complement radiosonde observations and for NWP model verification and process studies.
Highlights
Accurate and reliable measurements of the vertical wind profile are an essential meteorological observation, with respect to numerical weather prediction (NWP), climate modelling, air-quality monitoring and forecasting, and generation of energy forecasting
Doppler lidars have several advantages over radiosondes and radar wind profilers (RWP): (1) the lidar’s narrow beam removes the issue of ground clutter, making measurements possible in complex terrain [3,4,5,6,7,8]; (2) measurements can be taken in urban areas where radiosondes cannot be launched; (3) observations can be conducted during high surface winds when radiosondes cannot be launched; (4) they are deployable and can be mobile [7]; (5) they can take measurements below the height of the first range gate of most RWPs; (6) observations exhibit no measurement drift; and (7) the cost of a lidar system is typically less than a RWP while offering higher-resolution data
The mean bias between the lidar and radiosonde was −0.46 ± 0.02 m/s and −0.27 ± 0.02 m/s for Doppler beam-swinging (DBS) and velocity-azimuth display (VAD) scans, respectively, which falls within the quoted uncertainty by both manufacturers
Summary
Accurate and reliable measurements of the vertical wind profile are an essential meteorological observation, with respect to numerical weather prediction (NWP), climate modelling, air-quality monitoring and forecasting, and generation of energy forecasting. Available Doppler lidar wind profilers have proven their capability of measuring the wind speed and turbulence intensity with an accuracy comparable to the well-established cup anemometers over non-complex terrain [1,2]. Doppler lidars have several advantages over radiosondes and RWPs: (1) the lidar’s narrow beam removes the issue of ground clutter, making measurements possible in complex terrain [3,4,5,6,7,8]; (2) measurements can be taken in urban areas where radiosondes cannot be launched; (3) observations can be conducted during high surface winds when radiosondes cannot be launched; (4) they are deployable and can be mobile [7]; (5) they can take measurements below the height of the first range gate of most RWPs; (6) observations exhibit no measurement drift; and (7) the cost of a lidar system is typically less than a RWP while offering higher-resolution data. It should be noted that more powerful Doppler lidars, though rare, are capable of conducting measurements above the boundary layer [9]
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