Abstract
Previous studies have identified finely laminated, or layered, features within Arctic clouds. This study focuses on quasi-horizontal layers that are 7.5 to 30 m thick, within clouds from 0 to 5 km altitude. No pre-selection for any particular cloud types was made prior to the identification of laminations. We capitalize on the 4-year measurement record available from Eureka, Nunavut (79.6∘ N, 85.6∘ W), using the Canadian Network for the Detection of Atmospheric Composition Change (CANDAC) Rayleigh–Mie–Raman Lidar (CRL; 1 min, 7.5 m resolution). Laminated features are identified on 18% of all days, from 2016–2019. Their presence is conclusively excluded on 12% of days. March, April, and May have a higher measurement cadence and show laminations on 41% of days. Individual months show laminations on up to 50% of days. Our results suggest that laminations are not rare phenomena at Eureka. To determine laminations’ likely contribution to Arctic weather and climate, local weather reports were obtained from the nearby Environment and Climate Change Canada (ECCC) weather station. Days with laminated clouds are strongly correlated with precipitating snow (r = 0.63), while days with non-laminated clouds (r = −0.40) and clear sky days (r = −0.43) are moderately anti-correlated with snow precipitation.
Highlights
Arctic clouds generally warm the surface by trapping and re-emitting upwelling infrared radiation; except in summer, when they contribute a slight cooling by emitting more radiation to space than they reflect back to the surface [1,2]
To determine laminations’ likely contribution to Arctic weather and climate, local weather reports were obtained from the nearby Environment and Climate Change Canada (ECCC) weather station
Layers 100–200 m, as seen by Verlinde et al [11], are seen at Eureka. These larger layers are not the topic of the present study, as we focus on the new detections of the finer scale phenomena
Summary
Arctic clouds generally warm the surface by trapping and re-emitting upwelling infrared radiation; except in summer, when they contribute a slight cooling by emitting more radiation to space than they reflect back to the surface [1,2]. During the Arctic polar night, in the absence of incoming solar radiation, clouds can dominate the radiation budget; so, understanding their radiative impact is essential (e.g., [3,4,5,6]). Clouds govern precipitation and, are linked to local surface weather. Inhomogeneities within clouds, and the distribution of supercooled liquid water versus ice within mixed-phase clouds, are an important influence on weather and climate. The relative abundance of liquid versus ice controls the overall radiative balance via cloud optical depth effects [7]. Weather models depend on correct estimates of microphysical process rates for precipitation development, which themselves depend on measured vertical gradients of cloud properties [8]. The measurement of inhomogeneities, within clouds at all scales, is necessary
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