The growth of snow as seen by profiling radars -...
Transcript of The growth of snow as seen by profiling radars -...
The growth of snow The growth of snow as seen by profiling as seen by profiling
radarsradars
P. Kollias and I. ZawadzkiMcGill University
Arctic Cloud StationsBarrow
SHEBA
Eureka
Alert
Ny’Alesund
Tiksi
Radar Lidar
An Example Station
Slide provided by M. Shupe, NOAA
Radar
Lidar
• Very cloudy in general at all stations (~75% total)• Lots of low-level clouds• Liquid is present throughout the year more than half of the time!• Mixed-phase clouds: Maxima in transition seasons
Slide provided by M. Shupe, NOAA
High Spectral Resolution Lidarbackscatter
High Spectral Resolution Lidadepol
Millimeter-Wavelength Radar,backscatter
Millimeter-Wavelength Radarvelocity
Thin Liquid Layer ~ high
lidar
backscatter
Thin Liquid Layer ~ no
lidar depol
Thin Liquid Layer ~ Most of the time not detected
by MMCR’s
Thin Liquid Layerdetection required lidar
in space
Lessons LearnLessons Learned:ed:
1. Profiling radars give information on 1. Profiling radars give information on microphysics and dynamics of snow systemsmicrophysics and dynamics of snow systems
2. Snow exhibits great variability in 2. Snow exhibits great variability in typestypes and fromand from one location to anotherone location to another
3. Lowest km critical for determination 3. Lowest km critical for determination of snow amountof snow amount
4. 4. Low cost, low maintenance ground base Low cost, low maintenance ground base XX--band profiling radars could be deployed band profiling radars could be deployed in some high latitude locations which in some high latitude locations which would nicely complement spacewould nicely complement space--borne borne
systemssystems
Radar Requirements for Radar Requirements for spaceborne spaceborne polar polar hydrology missionhydrology mission
Sensitivity of Sensitivity of --15 dBZ is required to 15 dBZ is required to detect ice cloudsdetect ice clouds
Vertical Resolution of 100m is desirable Vertical Resolution of 100m is desirable to infer surfaceto infer surface snow amount and detect snow amount and detect
sublimationsublimation
Snow fall Doppler velocity range is 0.5Snow fall Doppler velocity range is 0.5--1.5 1.5 m/sm/s. . AnAn accuracy of 0.1 accuracy of 0.1 m/s m/s is is
required to infer snow microphysics and required to infer snow microphysics and system dynamicssystem dynamics
CloudSat
Radar frequency for detection
The sensitivity requirements -15 dBZ for ice cloud detection and -5 dBZ for snow detection (Joe, 2003) and the need to provide high vertical resolution and near the surface
observations can be achieved only with a 94-GHz radarCloudSat Snow Profiles CloudSat Rain Profiles
rimed
Non rimed
Interpretation of snow reflectivity depends on snow density:dual frequency gives information on density
Attenuation is negligible in snow; no
information from single frequency
Dreaming in two colors (13.4 and 94GHz band)