CIMO Survey National Summaries of Methods and Instruments Related to Solid Precipitation Measurement at Automatic Weather Stations - Very Preliminary results -

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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

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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.

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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)

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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

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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.

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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.

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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).

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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.

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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
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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.

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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.

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Message

• Additional responses are still expected and
  encouraged.
• Thank you!
• Rodica Nitu
• Meteorological Service of Canada
• Rodica.nitu_at_eg.gc.ca