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Blowing Snow Observations during ASCII. David Kristovich Prairie Research Institute University of Illinois. Related Goals in Proposal and Supplemental Request. To examine PBL turbulence as a mechanism of orographic precipitation growth

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slide1

Blowing Snow Observations during ASCII

David Kristovich

Prairie Research Institute

University of Illinois

Related Goals in Proposal and Supplemental Request

  • To examine PBL turbulence as a mechanism of
  • orographic precipitation growth
  • to examine the terrain surface as a source of ice crystals and
  • orographic cloud glaciation, through blowing snow and/or ice
  • multiplication
  • Better characterization of hydrometeors using superior probes at the mountain crest site
  • Dedicated King Air flights
slide2

Blowing Snow Observations during ASCII

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Horizontal transport, surface snow loss, change in snowpack characteristics

Modified from Chung, Y.-C., S. Bélair, J. Mailhot, 2011: Blowing Snow on Arctic Sea Ice: Results from an Improved Sea Ice–Snow–Blowing Snow Coupled System. J. Hydrometeor, 12, 678–689.

slide3

Blowing Snow Observations during ASCII

  • Objectives for ASCII
    • Understand vertical distribution of lofted ice particles throughout the mechanically-mixed BL
    • Understand BL structure, esp. vertical motions (fluxes?)

http://stoneroads.blogspot.com/2010_05_01_archive.html

  • Mountains & Plains
  • Refine observational techniques using relatively new facilities

http://impressions.v-infinity.net/2005_02_01_archive.html

slide4

Blowing Snow Observations during ASCII

  • Issues and Questions
    • Are snow crystals transported vertically far enough to be important to snow growth?
      • Entirely possible in mountainous regions
      • Possible in some circumstances over plains

Geerts, B., Q. Miao, Y. Yang, 2011: Boundary Layer Turbulence and Orographic Precipitation Growth in Cold Clouds: Evidence from Profiling Airborne Radar Data. J. Atmos. Sci., 68, 2344–2365.

slide5

Blowing Snow Observations during ASCII

  • Issues and Questions
    • Are snow crystals transported vertically far enough to be important to snow growth?
      • Entirely possible in mountainous regions
      • Possible in some circumstances over plains

http://lidar.ssec.wisc.edu/experiments/lakeice/highlights.htm

http://www.panoramio.com/photo/47539031

slide6

Blowing Snow Observations during ASCII

  • Issues and Questions
    • Are snow crystals transported vertically far enough to be important to snow growth?
      • Entirely possible in orographic systems
      • Possible in some circumstances
    • Are snow crystals transported vertically far enough to be observed?
      • WCR
        • Somewhat strong side lobes (17-19 dB lower than main lobe); least impact nadir antenna
          • Ground clutter 50 m to 200-300 m (Sam Haimov)
          • Check w/ non-blowing, non-snowing flight
        • 100 nanosec, 7.5 m sampling, 400 gates (3 km max)
        • along-flight sampling ≈ 5 m
        • surface effects on velocity field. BL motions?
slide7

Blowing Snow Observations during ASCII

  • Issues and Questions
    • Are snow crystals transported vertically far enough to be important to snow growth?
      • Entirely possible in orographic systems
      • Possible in some circumstances
    • Are snow crystals transported vertically far enough to be observed?
      • WCR - nadir
      • WCL - nadir
        • very high vertical resol. (3.75 m? Wang et al. 2009)
        • Information on snow profile. BL depth?
        • Return power, linear depolarization ratio
slide8

Blowing Snow Observations during ASCII

  • Issues and Questions
    • Are snow crystals transported vertically far enough to be important to snow growth?
      • Entirely possible in orographic systems
      • Possible in some circumstances
    • Are snow crystals transported vertically far enough to be observed?
      • WCR - nadir
      • WCL - nadir
      • UWKA in situ obs
      • Surface obs
        • Battle Pass (Bart)
        • SPEC Cloud Particle Imager (Paul Lawson)
blowing snow iops
Blowing Snow IOPs
  • Two 3-4 hr long flights, one under optimal blowing snow conditions, the other under packed snow. In both cases, clear sky (non-precipitating clouds OK)
  • Flight plan: single flight under VFR conditions
    • single pattern takes ~ 45 min
    • 3 complete patterns can be flown on a single flight, or parts of the pattern can be flown repeatedly
    • both flights should track the same waypoints
  • No RSE case (seeding activities irrelevant)
  • Case calling controlled by ASCII
  • Required weather conditions
    • clear sky (non-precipitating clouds OK) – VFR conditions
    • blowing snow flight:
      • fresh snow on the ground, cold, very windy
      • high humidity, possibly some orographic cloud over the SM
    • no-blowing-snow flight:
      • weak wind and/or snow surface crusting
  • Leg 1 of the blowing snow flight pattern can be flown as an alternate to the aerosol race tracks in a dual-flight IOP
  • GAUS soundings: two soundings per IOP, launched early and late into the flight
  • Battle Town site fully operational
  • NO DOW operations
blowing snow iops1
Blowing Snow IOPs
  • Two 3-4 hr long flights, one under optimal blowing snow conditions, the other under packed snow. In both cases, clear sky (non-precipitating clouds OK)
  • Flight plan: single flight under VFR conditions
    • single pattern takes ~ 45 min
    • 3 complete patterns can be flown on a single flight, or parts of the pattern can be flown repeatedly
    • both flights should track the same waypoints
  • No RSE case (seeding activities irrelevant)
  • Case calling controlled by ASCII
  • Required weather conditions
    • clear sky (non-precipitating clouds OK) – VFR conditions
    • blowing snow flight:
      • fresh snow on the ground, cold, very windy
      • high humidity, possibly some orographic cloud over the SM
    • no-blowing-snow flight:
      • weak wind and/or snow surface crusting
  • Leg 1 of the blowing snow flight pattern can be flown as an alternate to the aerosol race tracks in a dual-flight IOP
  • GAUS soundings: two soundings per IOP, launched early and late into the flight
  • Battle Town site fully operational
  • NO DOW operations

-20°C

Baggaley, D. G., J. M. Hanesiak, 2005: An Empirical Blowing Snow Forecast Technique for the Canadian Arctic and the Prairie Provinces. Wea. Forecasting, 20, 51–62.

blowing snow iops2
Blowing Snow IOPs
  • Two 3-4 hr long flights, one under optimal blowing snow conditions, the other under packed snow. In both cases, clear sky (non-precipitating clouds OK)
  • Flight plan: single flight under VFR conditions
    • single pattern takes ~ 45 min
    • 3 complete patterns can be flown on a single flight, or parts of the pattern can be flown repeatedly
    • both flights should track the same waypoints
  • No RSE case (seeding activities irrelevant)
  • Case calling controlled by ASCII
  • Required weather conditions
    • clear sky (non-precipitating clouds OK) – VFR conditions
    • blowing snow flight:
      • fresh snow on the ground, cold, very windy
      • high humidity, possibly some orographic cloud over the SM
    • no-blowing-snow flight:
      • weak wind and/or snow surface crusting
  • Leg 1 of the blowing snow flight pattern can be flown as an alternate to the aerosol race tracks in a dual-flight IOP
  • GAUS soundings: two soundings per IOP, launched early and late into the flight
  • Battle Town site fully operational
  • NO DOW operations