1 / 30

The NOAA/FAA/NCAR Winter Precipitation Test Bed: How Well Are We Measuring Snow?

The NOAA/FAA/NCAR Winter Precipitation Test Bed: How Well Are We Measuring Snow?. Roy Rasmussen 1 , Bruce Baker 2 , John Kochendorfer 2 , Tilden Myers 2 , Scott Landolt 1 , Alex Fisher 3 , Jenny Black 1 , Julie Theriault 1 , Paul Kucera 1 , David Gochis 1 , Craig Smith 3 ,

irma
Download Presentation

The NOAA/FAA/NCAR Winter Precipitation Test Bed: How Well Are We Measuring Snow?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The NOAA/FAA/NCAR Winter Precipitation Test Bed:How Well Are We Measuring Snow? Roy Rasmussen1, Bruce Baker2, John Kochendorfer2, Tilden Myers2, Scott Landolt1, Alex Fisher3, Jenny Black1, Julie Theriault1, Paul Kucera1, David Gochis1, Craig Smith3, Rodica Nitu3,Mark Hall2,Steve Cristanelli1 and Ethan Gutmann1 1. National Center for Atmospheric Research (NCAR) 2. NOAA 3. Environment Canada t

  2. The NOAA/FAA/NCAR Winter Precipitation Test Bed:How Well Are We Measuring Snow? Roy Rasmussen1, Bruce Baker2, John Kochendorfer2, Tilden Myers2, Scott Landolt1, Alex Fisher3, Jenny Black1, Julie Theriault1, Paul Kucera1, David Gochis1, Craig Smith3, Rodica Nitu3,Mark Hall2,Steve Cristanelli1 and Ethan Gutmann1 1. National Center for Atmospheric Research (NCAR) 2. NOAA 3. Environment Canada t

  3. The NOAA/FAA/NCAR Winter Precipitation Test Bed was initially established in 1991 at NCAR in Boulder, Colorado to address FAA needs for real-time snowfall rates in support of ground deicing The NOAA Climate Reference Network program started using the site in the late 90’s to evaluate snow measuring instrumentation for climate purposes (Bruce Baker, lead).

  4. Challenges of automatic snow fall rate measurements: • Wind under-catch • - Gauge acting as obstacle to the flow, generating updrafts • Cap over of the orifice by snow accumulating on the gauge • Minimum detectable signal often large (to overcome noise) • Minimum detectable signal impacted by wind speed (higher the wind, the larger the minimum detectable signal) • Eliminating blowing snow false accumulations • High maintenance • Need to empty the bucket after snow fills up and refill bucket with glycol and oil.

  5. Updraft generated upstream of gauge

  6. To address these challenges, developed the NOAA/FAA/NCAR Solid Precipitation Test Site near Boulder, Colorado Insert image of the Marshall site with DFIR Core to the site: Double Fence Inter-comparison Reference (DFIR) shields as “truth” gauge

  7. Layout of site: Flat and level site located 7 km south of Boulder, Colorado NCAR owned and operated with security fence

  8. Aerial View of the NOAA/FAA/NCAR Test site

  9. View of test site to the South

  10. View of test site towards the West

  11. Developed and tested double Alter shield

  12. Developed and tested 2/3 DFIR shield (CRN)

  13. Developed and tested hotplate snowgauge

  14. Testing multiple hotplates

  15. Documented snow under-catch behavior of various shields and gauges Hotplate DFIR Small DFIR Wind speed Double Alter Single Alter

  16. Established transfer functions for various shields and gauges

  17. Data used to develop transfer function shows significant scatter!

  18. Thank You! Rasmussen et al. 2001

  19. Numerical studies of flow past various shield/gauge combinations help explain scatter(Julie Therialt talk later in this session)

  20. 1.7 mm/hr Moderate LGT MOD HVY Established that visibility is a poor method to estimate the liquid equivalent rate of snow (light, moderate, heavy)

  21. Developed and tested the Liquid Water Equivalent system for ground deicing use

  22. Developed method to heat the orifice of a gauge using temperature controlled heat tape (max temperature 2 ˚C)

  23. Precipitation Type sensor (HSS) Precipitation Type sensor (Vaisala PWD-22) Moderate Snow Snow Liquid Water Equivalent System WXT temperature, humidity, and wind sensor (Vaisala) Hotplate (Yankee) Liquid Equivalent snowfall rate determination Weighing Snowgauge (GEONOR)

  24. Aircraft Deicing Fluid testing

  25. Accurate snow depth measurements remain a challenge!

  26. Summary • The NOAA/FAA/NCAR Winter Precipitation Test Bed has been used to investigate a number of important aspects of winter precipitation: • Under-catch of snow as a function of shield type and the development of transfer functions • Develop and test new wind shields • Evaluate the use of various gauge/shield combinations for both real-time and climate snow measurements. • Develop and test new precipitation instruments (hotplate) • Real-time measurement of snow for aircraft ground deicing purposes • The use of visibility to measure snow intensity • Snow size distributions and terminal velocity • Radar- reflectivity snowfall relationships

  27. Summary • How well are we measuring snow? • While advances in shields and gauges have been made, we still don’t fully understand the significant scatter in the data nor have we designed the perfect wind shield to reduce the scatter. • Need to use direct measurements of the liquid equivalent rate of snow to estimate snow intensity in METARs rather than use visibility • The automated measurement of precipitation type and snow depth remains a significant challenge. • The upcoming WMO Solid Precipitation Intercomparison Experiment mentioned by Rodica can help address these challenges.

  28. Thank You!

More Related