Multi‐Instrument Observations of Prolonged Stratified Wind Layers at Iqaluit, Nunavut

Mariani, Zen; Dehghan, Ali Akbar; Gascon, Gabrielle; Joe, Paul; Hudak, David; Strawbridge, K. B.; Corriveau, Julien

doi:10.1002/2017gl076907

Cited by 15 publications

(13 citation statements)

References 29 publications

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“…The sharp drop in comparisons at 900 m AGL in Figure 6b is attributed to the steep decrease in available DIAL observations (<40% at 1 km AGL) in Figure 8. Correspondingly, this occurs around the maximum PBL height (depending on the season) that has been observed at Iqaluit [45]. The DIAL's night-time data availability (matching the same observing period as the CAAAL) was similar to the DIAL's 24 h all-year data availability, except for a slightly greater maximum vertical range during the night time.…”

Section: Dial Caaal and Radiosonde Comparisonssupporting

confidence: 53%

“…This demonstrates the usefulness of the DIAL's 24 h observations, its ability to measure fast-moving meteorological features and steep gradients in the WVMR profile, and its ability to fill the temporal gap in water vapor profile observations at WMO RS observation sites. This is particularly important for Iqaluit, where persistent stratified wind and water vapor layers can cause larger model forecast errors [45].…”

Section: Discussionmentioning

confidence: 99%

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Evaluation of Arctic Water Vapor Profile Observations from a Differential Absorption Lidar

et al. 2021

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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.

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Section: Dial Caaal and Radiosonde Comparisonssupporting

confidence: 53%

Section: Discussionmentioning

confidence: 99%

Evaluation of Arctic Water Vapor Profile Observations from a Differential Absorption Lidar

et al. 2021

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“…The DIAL has remained at Iqaluit to this day, performing exceptionally well, collecting observations on a continuous basis in the harsh Arctic climate without any technical issues (100% up-time with the exception of power outages at the site). The DIAL's high temporal and spatial observations in the Arctic will be used to investigate prolonged stratified wind and water vapor layers above the Iqaluit site [29], the diurnal water vapor cycle, perform side-by-side comparisons to radiosonde observations and a Raman water vapor lidar co-located at the site for a detailed instrument validation study, and for NWP model verification and assimilation impact studies.…”

Section: Discussionmentioning

confidence: 99%

Toronto Water Vapor Lidar Inter-Comparison Campaign

et al. 2020

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This study presents comparisons between vertical water vapor profile measurements from a Raman lidar and a new pre-production broadband differential absorption lidar (DIAL). Vaisala’s novel DIAL system operates autonomously outdoors and measures the vertical profile of water vapor within the boundary layer 24 h a day during all weather conditions. Eight nights of measurements in June and July 2018 were used for the Toronto water vapor lidar inter-comparison field campaign. Both lidars provided reliable atmospheric backscatter and water vapor profile measurements. Comparisons were performed during night-time observations only, when the York Raman lidar could measure the water vapor profile. The purpose was to validate the water vapor profile measurements retrieved by the new DIAL system. The results indicate good agreement between the two lidars, with a mean difference (DIAL–Raman) of 0.17 ± 0.09 g/kg. There were two main causes for differences in their measurements: horizontal displacement between the two lidar sites (3.2 km) and vertical gradients in the water vapor profile. A case study analyzed during the campaign demonstrates the ability for both lidars to measure sudden changes and large gradients in the water vapor’s vertical structure due to a passing frontal system. These results provide an initial validation of the DIAL’s measurements and its ability to be implemented as part of an operational program.

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“…The CAWS project, led by ECCC, aims to characterize and improve scientific understanding of Arctic weather, climate, and cryospheric systems through enhanced meteorological observation capacity (Joe et al, 2020;Mariani et al, 2018). It also seeks to improve weather forecasts in the Canadian Arctic, test new technologies, and calibrate and validate space-based observations.…”

Section: Ground-based Measurements At Iqaluit Whitehorse and Other Radiosonde Stationsmentioning

confidence: 99%

“…Vaisala RS92 radiosondes (Mariani et al, 2018) were launched twice daily at and 12 Coordinated Universal Time (UTC).…”

Section: Ground-based Measurements At Iqaluit Whitehorse and Other Radiosonde Stationsmentioning

confidence: 99%

Validation of the Aeolus Level-2B wind product over Northern Canada and the Arctic

Chou

Kushner

Laroche

et al. 2021

Preprint

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Abstract. In August 2018, the European Space Agency launched the Aeolus satellite, whose Atmospheric LAser Doppler INstrument (ALADIN) is the first spaceborne Doppler wind lidar to regularly measure vertical profiles of horizontal line-of-sight (HLOS) winds with global sampling. This mission is intended to assess improvement to numerical weather prediction provided by wind observations in regions poorly constrained by atmospheric mass, such as the tropics, but also, potentially, in polar regions such as the Arctic where direct wind observations are especially sparse. There remain gaps in the evaluation of the Aeolus products over the Arctic region, which is the focus of this contribution. Here, an assessment of the Aeolus Level-2B wind product is carried out from measurement stations in Canada’s north, to the pan-Arctic, with Aeolus data being compared to Ka-band radar measurements at Iqaluit, Nunavut; to radiosonde measurements over Northern Canada; to Environment and Climate Change Canada (ECCC)’s short-range forecast; and to the reanalysis product, ERA5, from the European Centre for Medium-Range Weather Forecasts (ECMWF). Periods covered include the early phase during the first laser nominal flight model (FM-A; 2018-09 to 2018-10), the early phase during the second flight laser (FM-B; 2019-08 to 2019-09), and the mid-FM-B periods (2019-12 to 2020-01). The adjusted r-square between Aeolus and other local datasets are around 0.9, except for somewhat lower values in comparison with the ground-based radar, presumably due to limited sampling. This consistency degraded by about 10 % for the Rayleigh winds in the summer, presumably due to scattering from the solar background. Over the pan-Arctic, consistency, with correlation greater than 0.8, is found in the Mie channel from the planetary boundary layer to the lower stratosphere (near surface to 16 km a.g.l.) and in the Rayleigh channel from the troposphere to the stratosphere (2 km to 25 km a.g.l.). Zonal and meridional projections of the HLOS winds are separated to account for the systematic changes in HLOS winds arising from sampling wind components from different viewing orientations in the ascending and descending phases. In all cases, Aeolus standard deviations are found to be 20 % greater than those from ECCC-B and ERA5. We found that L2B estimated error product for Aeolus is coherent with the differences between Aeolus and the other datasets, and can be used as a guide for expected consistency. Thus, our work confirms the quality of the Aeolus dataset over the Arctic and shows that the new Aeolus L2B wind product provides a valuable addition to current wind products in regions such as the Arctic Ocean region where few direct wind observations have been available to date.

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Multi‐Instrument Observations of Prolonged Stratified Wind Layers at Iqaluit, Nunavut

Cited by 15 publications

References 29 publications

Evaluation of Arctic Water Vapor Profile Observations from a Differential Absorption Lidar

Evaluation of Arctic Water Vapor Profile Observations from a Differential Absorption Lidar

Toronto Water Vapor Lidar Inter-Comparison Campaign

Validation of the Aeolus Level-2B wind product over Northern Canada and the Arctic

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