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How well are we measuring snow?

WMO Intercomparison of Instruments and methods for the Measurement of Solid Precipitation and Snow on the Ground, WMO-SPICE: Pre-SPICE Studies

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How well are we measuring snow?

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  1. WMO Intercomparison of Instruments and methods for the Measurement of Solid Precipitation and Snow on the Ground, WMO-SPICE: Pre-SPICE Studies R. Rasmussen(1) ,R. Nitu (2),B. Baker(3),E Lanzinger (4),D Yang(7),C Smith(7),Y.A. Roulet(5),B Goodison((15) ,H Liang(6),F Sabatini(8),J Kochendorfer(3),M Wolff(9) ,J Hendrikx (10), E Vuerich(11),L Lanza(12),P. Joe(2),O Aulamo(13),V Vuglinsky(14) , Michael Earle(2) ,Jeffery Hoover(2), S Landolt(1) (1) National Center for Atmospheric Research, Boulder, USA, rasmus@ucar.edu(2) Environmemt Canada, Toronto, Canada, Rodica.nitu@ec.gc.ca, 3) NOAA Air Resources Laboratory, Oak Ridge, TN, 37830 ,4)DeutscherWetterdienst, Hamburg, Germany,(5)MétéoSuisse,PAYERNE, Switzerland, (6)China Meteorological Administration, BEIJING, China. 7)Environment Canada, Saskatoon, Canada . (8) CNR-IBIMET, Institute of Biometeorology, Florence, Italy, (9)Norwegian Meteorological Institute,Oslo, Norway, (10)Montana State University, Montana, U.S.A., (11) Italian Met Service – Air Force, Centre of Meteorological Experimentations, Vignadi Valle (Rome) Italy, 12) DICAT - Department of Civil, Environmental and Territorial Engineering, University of Genoa , GENOVA Italy , 13) Finnish Meteorological Institute, Arctic Research Centre, Sodankyla , (14) State Hydrological institute,St.Petersburg, Russian Federation, (15) World meteorological Organization, EC-PORS, GCOS, GenevaSwitzerland

  2. How well are we measuring snow?

  3. Challenge to Measuring Snowfall Updraft generated upstream of gauge

  4. Due to updraft, snowgauges significantly undercatch Data from single alter GEONOR gauge at Marshall (box plots) Model results (lines) from Fluent simulation of flow past single Alter GEONOR with snowflake trajectory modeling Single Alter GEONOR Theriault et al. 2011

  5. Challenges to Measuring Snowfall Capping of gauge

  6. Key goal of Pre-SPICE: Establish Field Reference Systems for SPICE • Need to establish a recognized field reference using automatic gauges to calculate the undercatch as a function of wind speed (transfer function). • Proposed configuration: DFIR shield surrounding a Weighing Gauge (WG) • Develop transfer functions to characterize the proposed reference against the WMO Secondary Reference (Tretyakov gauge inside DFIR); • Options for the configuration of a Filed Reference using WG: • Type of WG: proposed Geonor T-200, OTT Pluvio 2; • Configuration of WG: • heated/non-heated; • wind shield: • DFIR, • Double Alter, Belfort Double Alter.

  7. Instruments and Site Focus for Pre-SPICE • A WMO secondary field reference, using a manual Tretyakov gauge installed in a DFIR, was used in Canada and Finland. • A DFIR shield surrounding an automatic precipitation weighing gauge was configured and assessed as a field working reference in Canada (CARE and Bratt’s Lake), Finland (Jokioinen), Norway (Haukeliseter), and USA (Boulder),(DFAR) • In Switzerland, the focus of the pre-SPICE experiment was the assessment of the heating of a weighing gauge, in alpine conditions, in the presence of large amounts of snowfall. • A laboratory calibration of the instruments considered for use as part of the working field reference was performed at the Precipitation Intensity Lead Centre in Genoa (Italy). This focused on the testing of the weighing gauges at temperatures representative of the winter operating conditions. Week long meeting was held the week of June 11th in Boulder, Colorado to review the results of the Pre-SPICE testing

  8. Current reference for snowfall observations are manual Bush Gauge Primary Reference (Valdai, Russia) Only one!

  9. Secondary Reference: DFIR surrounding a Tretyakov precipitation gauge • WMO Solid Precipitation Measurement Inter-comparison (WMO CIMO IOM Report No. 67, WMO/TD-No. 872, 1998 http://www.wmo.int/pages/prog/www/IMOP/publications/IOM-67-solid-precip/WMOtd872.pdf) • Recommended : “The Double Fence Intercomparison Reference (DFIR) should be accepted as a secondary reference for the (manual) measurement of solid precipitation;” (section 6.1.2) • (DFIR): “The octagonal vertical double-fence inscribed into circles 12 m and 4 m in diameter, with the outer fence 3.5 m high and the inner fence 3.0 m high surrounding a Tretyakov precipitation gauge mounted at a height of 3.0 m.”( section 2.2.2) Double Fence Intercomparison Reference

  10. Cross section of DFIR shield

  11. Pre-SPICEWinter 2011-2012 Set-up and some results from Weissfluhjoch/Davos 11.6.2012

  12. Testing at Davos, Switzerland by MeteoSwiss - Impact of heating on OTT Pluvio2 200 cm2 gauge with Tretyakov shield

  13. 21.02.2012

  14. Schematic of ice bridging inside the OTT PLUVIO2

  15. Summary of Testing at Switzerland Impact of heating unshielded OTT Pluvio2 200 cm2 gauge 1. For prevailing alpine conditions, measurement is difficult with an unheated gauge: snow can induce mechanical effects on the sensor, with possible formation of ice or snow bridges between the housing and the weighing elements. 2. Heating of the ring is mandatory to ensure good quality measurements in Alpine winter conditions with high snow amount. 3. No under-catch due to the heating.

  16. Jokioinen: Pre-SPICE field 60° 48' 50.44" N, 23° 29' 51.40” E, 104 m, from the sea level Measurements 19.02.2012 – 30.04.2012 Manual measurements only once every day at 0600 UTC Compared manual measurement in DFIR with Tretyakov shield and can with automated measurement in DFIR with OTT Pluvio2 gauge Finnish Meteorological Institute

  17. Rain Both gauges in DFIR Finnish Meteorological Institute

  18. Snow Both gauges in DFIR Finnish Meteorological Institute

  19. Results from testing in Finland: The daily precipitation amount from the automated gauge in the DFIR compared well with the manual measurement from the Tretyakov can also in a DFIR. Suggests that can use an automated gauge in a DFIR as a reference for SPICE (DFAR). Finnish Meteorological Institute

  20. Summary of results from the Canadian contribution to Pre-SPICE Rodica Nitu, Paul Joe, Daqing Yang, Craig Smith, Michael Earle, Jeff Hoover, Jim Waller, Faisal Boudala Toward the definition of a SPICE field reference Pre-SPICE Workshop Boulder, Colorado June 11, 2012

  21. Measurements from two field sites Canada Bratt’sLake CARE • Centre for Atmospheric Research Experiments (CARE) • Egbert, Ontario CARE • Bratt’s Lake (BL) • Bratt’s Lake, Saskatchewan Bratt’s Lake

  22. Instruments at the Canadian CARE site Tretyakov manual gauge in DFIR Geonor T-200 heated (DFIR) Pluvio 2 (Belfort Double Alter) Geonor T-200 in BDA

  23. The Bratt’s Lake Precipitation Intercomparison Facility • Bratt’s Lake, Saskatchewan: • Under test: • Unheated Geonor in a DFIR • Heated Geonor (using the CRN heating algorithm), in a DFIR Heated Geonor gauge (CRN heating) Unheated Geonor gauge

  24. Summary of Canadian Pre-SPICE testing • Rim heating has a positive impact on the gauge performance (accuracy, improved catch), both GEONOR T-200 or OTT PLUVIO2. • Both GEONOR T-200 and OTT PLUVIO2 performed well in terms of accuracy • Either GEONOR T-200 or OTT PLUVIO2 acceptable at weighing gauge for Field Reference

  25. Marshall (Boulder, CO USA) site with DFIR and Alter shielded snow guages

  26. Summary of Pre-SPICE Results from Marshall Field Site, USA 1. Gauge performance in Small DFIR and standard DFIR similar in terms of accuracy. 2. Provided estimate of the performance of various wind shield types. 3. Noted the importance of heating the entire collection tube of the GEONOR T-200 gauge. 4. Noted that the current OTT PLUVIO2 heating algorithm may not be sufficient for heavy, wet snow conditions (dumps occurred in this situation).

  27. Test site Haukeliseter, NorwayPre-SPICE Data Mareile Wolff, Ketil Isaksen, Ragnar Brækkan Norwegian Meteorological Institute, Oslo, Norway

  28. Haukeliseter 59°48.71’N, 7°12.86’E, 991m

  29. Summary Identified the need for improved identification of the onset and offset of weak precipitiation events - Suggested use of a precipitation detector, yes/no sensor, video camera Blowing snow needs to be taken into account in open, high alpine sites

  30. WMO-CIMO LEAD CENTRE“BENEDETTO CASTELLI”ON PRECIPITATION INTENSITYITALY Laboratorytestsof SPICE referenceinstruments 2nd WMO SPICE, Boulder ,CO, USA, 11-15 June 2012

  31. Experiment setupTemperature tests Gauges in the cold chamber Set-up for OTT Set-up for Geonor

  32. Conclusions 3/3 • The dynamic tests show that both gauges are able to reproduce likely real world events with comparable performance; • The results from laboratory tests open the way for possible improvements of their accuracy and precision (including low intensities, the interest for SPICE) • The Lead Centre is currently conducting additional tests. • Matteo Colli from the U. of Genoa is currently visiting NCAR and testing the GEONOR T-200 gauge with the NCAR snow machine for heater performance for various snowfall rate and temperature conditions (snow capping elimination).

  33. Reference Systems for SPICE • LWE Precipitation Amount

  34. Working Field Reference for Precipitation Amount As agreed during the Boulder Meeting June 2012 • R1: DFIR + Tretyakov gauge (manual measurements) + Tretyakov shield designated in the 1989-1993 intercomparison as secondary field reference WMO/TD-872/1998); • R2: DFIR + automatic weighing gauge (AWG) + shield • Shield will be an Alter shield • Either GEONOR T-200 or OTT PLUVIO2 acceptable as the weighing gauge • Both gauges will be heated with the CRN heating algorithm (heat between +2 and -5 C, every 24 hours otherwise) • A capacitive precipitation detector will be used to detect the presence of precipitation

  35. Working Field Reference for Precipitation Amount As agreed during the Boulder Meeting June 2012 • R3: An automatic weighing gauge in a (small) windshield paired with an unshielded gauge • - The Working Field Reference System type R3 consists of a pair of identical automatic weighing gauges heated in the same manner, one being unshielded and the second installed with a single Alter Shield. The configuration of the Alter shield is specified by the SPICE IOC. Gauge type: GEONOR T-200 or OTT PLUVIO2 • - A capacitive precipitation detector will be used to detect the presence of precipitation. + + A

  36. How well are we measuring snow? Hopefully, after SPICE a lot better!

  37. Thank You! http://www.wmo.int/pages/prog/www/IMOP/reports/2011/Joint_ET-II_IOC-SPICE.pdf rasmus@ucar.edu

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