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CIMO SurveyNational Summaries of Methods and Instruments Related to Solid Precipitation Measurement at Automatic Weather Stations- Very Preliminary results -
R Nitu, G Fournier
WMO/CIMO - TECO St Petersburg, Nov 29, 2008
Page 2 DRAFT - DATE
Scope
• The fourteenth session of the WMO CIMO (CIMO-XIV), has tasked the Expert Team on Surface-Based Instrument Intercomparisons and Calibration Methods, to assess the needs and methods of measurement and observation of solid precipitation at automatic stations:
– Preparing national summaries of methods, issues and challenges;
– Updating metadata related to precipitation measurement instrumentation at all NMHS AWS;
– Documenting the needs of WMO Technical Commissions and Programs;
– Compiling measurement standards and requirements of WMO Technical Commissions.
– Assessing the need for an intercomparison of methods and equipment for automatic snowfall, snow depth, precipitation measurements, and develop an intercomparison plan.
Page 3 DRAFT - DATE
1986-1993 WMO Solid Precipitation Measurement Intercomparison
• assessed national methods of measuring solid precipitation against methods of known accuracy and reliability (primarily manual);
• determined wind related errors in national methods of measuring solid precipitation;
• derived standard methods for adjusting solid precipitation measurements;
• introduced a reference method of solid precipitation measurement for general use to calibrate any type of precipitation gauge.
• Final report: WMO/TD- No. 872, 1998, WMO Solid Precipitation Measurement Intercomparison, by B.E. Goodison and P.Y.T. Louie (both Canada), and D. Yang (China)
Page 4 DRAFT - DATE
2008 CIMO Survey on Methods and Instruments for Solid Precipitation
• Distributed July 2008, through CIMO Secretariat.
• Response deadline: Sept 15, 2008
• Goals of the survey:– the extent of measuring solid precipitation using automatic
instruments;– parameters measured, instruments used and their
configuration;– Identify adjustments applied to precipitation measurements;– Summary of derived solid precipitation parameters from
automatic stations measurements;– Summary of testing/developing new instruments and methods
of measurement of solid precipitation parameters
Page 5 DRAFT - DATE
Preliminary Results
• By mid October 2008: – 51 Member countries responded to the 2008 CIMO
Questionnaire (40% of the global landmass)– 45 respondents provided detailed information on their
precipitation measurement programs, a combination of manual observations and automatic instruments:
▪ 27,812 stations,
▪ Average density 1 station/1280 sq Km).
– 32 of the respondents measure solid precipitation:▪ 13,614 stations
▪ Average density: 1 station/2097 sq Km.
• Additional responses are still encouraged.
Page 6 DRAFT - DATE
Measurement synopsis
• Of the 45 Member countries providing detailed information on their measurement programs:
– 45, measure Accumulated Precipitation (100%);– 27, measure Depth of snow on the ground (60%);– 13, measure Snowfall amount (29%);– 17, measure Snow water equivalent (38%).
• Note: various parameters are monitored in various countries.
Page 7 DRAFT - DATE
Use of automatic instruments
• 30 responding Member countries operate automatic instruments at 6590 stations (24% of stations included in the survey).
– Many of the automatic precipitation instruments operate in conjunction with a human observation program.
• Reporting of snow parameters, from 13,614 stations:– 10% of stations use automatic sensors.– 90% of stations use manual measurements
• 10 Member countries use automatic snow depth sensors
• 3 Member countries derive snowfall using data from automatic instruments (Canada, Germany, Japan).
Page 8 DRAFT - DATE
Measuring total precipitation accumulation: instruments in use
• Of the 6590 stations using automatic instruments for measuring total precipitation accumulation:
– 14% use weighing type gauges:▪ used in 15 NMHSs,
▪ from 5 different manufacturers (Geonor, OTT, Vaisala, MPS Systems, and Belfort);
▪ All are used with shields (Alter, Tretyakov).
– 86% use tipping bucket type gauges, ▪ Used in 18 countries
▪ 23 different types of instruments.
▪ The majority have heating circuits.
Page 9 DRAFT - DATE
Measuring snow on the ground: instruments in use
Instruments in use:
• Sonic ranging sensors– SR-50 from Campbell Scientific,
most widely used (488 stations)– Sommer Ultrasonic snow depth
sensor USH-8, – MPS System SwS-3, – Ultrasonic snow level meter
Ogasawara Keiki Seisakusho JMA-95-1,
– Ultrasonic Kaijo Sonic JMA-89, JMA-93, JMA-04-1.
SR-50:
Page 10 DRAFT - DATE
Next steps
• Complete analysis of the results: first half of 2009
• Final report on the Questionnaire results: mid 2009.
• Evaluation of results by the Expert team on Surface Instrument Intercomparison and Calibration Methods.
• In cooperation with their representatives, document the needs of WMO Technical Commissions and Programs, regarding precipitation measurement.
• Assess the need for an intercomparison of methods and equipment for automatic snowfall, snow depth, precipitation measurements.
Page 11 DRAFT - DATE
Intercomparison?
Potential Outcomes:• Understand the performance of measurement of gauges in use.
• The efficiency of shields for precipitation gauges, in particular those measuring solid precipitation (snow).
• The re-evaluation of the Double Fence Intercomparison Reference (DFIR) using automatic gauges.
• Development of adjustment curves using hourly precipitation and 2-meter wind during the precipitation events.
Page 12 DRAFT - DATE
Message
• Additional responses are still expected and encouraged.
• Thank you!
Rodica Nitu
Meteorological Service of Canada