Multi-Instrument Observations of Prolonged Stratified Wind Layers at the Iqaluit Supersite

Environment and Climate Change Canada commissioned a supersite in Iqaluit, NU (64^oN, 69^oW) in 2015 to provide automated and continuous observations of altitude-resolved winds, clouds and aerosols, visibility, radiation fluxes, turbulence, and precipitation. This presentation will describe the suite of remote-sensing instruments at the Iqaluit site, their ability to detect and track the evolution of stratified wind layers, and present case studies of stratification events. Data collected between October 2015 and January 2017 from these ground-based observations have revealed a high frequency (40% daily occurrence) of stratified wind layer events that occur from near the surface up to 7.2 km a.g.l. These stratified wind layers are clearly visible as shifting wind directions with height in Doppler lidar and Doppler dual-polarization Ka-band radar range-height indicator scans and sharp changes (90 to 180^o) in the Doppler lidar and radiosonde wind direction profiles. During these events, the vertical structure of the flow appears to be a stack of four to 10 layers ranging in width from 0.2 to 4.4 km. Average radial velocities were 4.8 m/s at the midpoint of each layer. The stratification events that were observed occurred predominantly during light precipitation and lasted an average of nine hours. The benefit of integrated measurement systems and coordinated scan strategies at Iqaluit will be demonstrated in this presentation as the evolution of these stratified layers were measured continuously in different meteorological conditions. Given the prevalence of these stratification events at Iqaluit, prolonged stratified wind layers can have important consequences on aviation and weather forecasts in the local region and, potentially, other Arctic regions.