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Jasmine R émillard and Pavlos Kollias McGill University

Cloud Climatology and Microphysics at Eureka Using Synergetic Measurements from a Cloud Radar and a Cloud-Aerosol Lidar. Jasmine R émillard and Pavlos Kollias McGill University. Locating Eureka. 79.9903°N 85.9389°W. ~2km. ~1.5km. ~600m. ~1.5km. ~1.5km. courtesy of the Atlas of Canada.

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Jasmine R émillard and Pavlos Kollias McGill University

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  1. Cloud Climatology and Microphysics at Eureka Using Synergetic Measurements from a Cloud Radar and a Cloud-Aerosol Lidar Jasmine Rémillard and Pavlos Kollias McGill University

  2. Locating Eureka 79.9903°N 85.9389°W ~2km ~1.5km ~600m ~1.5km ~1.5km courtesy of the Atlas of Canada courtesy of CANDAC Scale 1:5 000 000 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  3. Instrumentation Millimeter wave cloud radar (MMCR) • active and vertically pointing • 8.66mm or 34.86GHz (Ka) • 10s and 45m resolutions (interpolated to the lidar’s for the synergistic) • provided by M. Shupe High spectral resolution lidar (HSRL) • active and vertically pointing • 532nm (green) • 0.5s and 7.5mresolutions (used with 180s and 30m) • provided by E. Eloranta Rawinsondes • launched at Eureka’s weather station (~1 km South) • interpolated to the lidar’s resolutions • mainly for the temperature profiles in the phase classification 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  4. Example of measurements lidar’s (sensitive to droplets) radar’s (sensitive to crystals) temperatures 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  5. Objectives • characterize the clouds and precipitation at Eureka • occurrence, overlap, type, phase… • 2-year period (September 2005-2007) • present some results and their analysis • BL clouds • supercooled liquid hydrometeors 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  6. Methodology – Phases • Above 0°C, everything should melt • Below -40°C, every nucleus is assumed to form ice on it • Populous particles dominate the lidar backscatter signal • Thus, in mixed-phase conditions, spherical liquid droplets keep the lidar depolarization low 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  7. 2-year results – hydrometeor phases fraction of hydrometeors, at a given height (lines are isotherms: -40, -20, 0°C) fraction of time that liquid was observed at any height 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  8. 2-year observation of liquid 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  9. Height of the liquid Winter Summer 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  10. Consistency supercooled liquid (12.3%) solid above -40°C (87.7%) 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  11. In a profile, an hydrometeor layer is defined as a group of consecutive gates that all have a radar reflectivity greater than -60 dBZ. 2-year results – number of layers 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  12. Methodology – Types • and everything below the lidar liquid base is assumed to be precipitating • definition of the cloud types based on the cloud base and top heights • base = lowest height without precip within the layer • top = highest radar echo within the layer 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  13. 2-year results – type of clouds 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  14. BL clouds occurrence 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  15. BL clouds persistence Different daily thresholds 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  16. A persistent mixed BL cloud Radar echo top Lidar liquid base Radar echo base 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  17. Analysis of the liquid base snow …and at night! more turbulent near top… 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  18. Summary • Clouds are a predominant feature at Eureka • more than 60% of most months • usually in single-layer systems • Hydrometeors are usually in their solid phase, but supercooled liquid is also found • ice clouds are less turbulent, but have greater velocities • normally at temperature greater than -20°C and high relative humidity • Types of clouds are seasonal-dependant (higher in summer…) • Mixed-phase BL clouds seem to be driven by the turbulence at their top 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

  19. Future work • Add more persistent BL cases in their analysis • Use CloudSat and CALIPSO data to see if those results stand for a larger area than just Eureka • Compare with the results obtained during other campaigns (SHEBA, NSA site…) 4th pan-GCSS meeting, Polar Cloud Working Group Toulouse, France

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