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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. - PowerPoint PPT Presentation
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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
Scale 1:5 000 000courtesy of the Atlas of Canada
~2km
~1.5
km
~1.5km
~600m
~1.5
km
Locating Eureka
vendredi 21 avril 20234th pan-GCSS meeting, Polar Cloud Working Group
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courtesy of CANDAC
79.9903°N 85.9389°W
InstrumentationMillimeter 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
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
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High spectral resolution lidar (HSRL)
• active and vertically pointing
• 532nm (green)
• 0.5s and 7.5m resolutions (used with 180s and 30m)
• provided by E. Eloranta
Example of measurements
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radar’s(sensitive to crystals)
lidar’s(sensitive to droplets)
temperatures
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
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Methodology – Phases
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Populous particles dominate the lidar backscatter signal
Thus, in mixed-phase conditions, spherical liquid droplets keep the lidar depolarization low
Above 0°C, everything should meltBelow -40°C, every nucleus is assumed
to form ice on it
2-year results – hydrometeor phases
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fraction of hydrometeors, at a given height (lines are isotherms: -40, -20, 0°C)
fraction of time that liquid was observed at any height
2-year observation of liquid
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Height of the liquid
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Winter Summer
Consistency
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supercooled liquid (12.3%)solid above -40°C (87.7%)
2-year results – number of layers
• In a profile, an hydrometeor layer is defined as a group of consecutive gates that all have a radar reflectivity greater than -60 dBZ.
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Methodology – Types
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and everything below the lidar liquid base is assumed to be precipitating
definition of the cloud types based on the cloud base and top heightsbase = lowest height without precip within the layertop = highest radar echo within the layer
2-year results – type of clouds
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BL clouds occurrence
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BL clouds persistence
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Different daily thresholds
A persistent mixed BL cloud
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Radar echo top
Lidar liquid base
Radar echo base
Analysis of the liquid base
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snow
more turbulent near top…
…and at night!
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
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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…)
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