R Nitu Meteorological Service of Canada AMS, Phoenix, AZ 12 Jan 2009
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Transcript of R Nitu Meteorological Service of Canada AMS, Phoenix, AZ 12 Jan 2009
WMO CIMO SurveyNational Summaries of Methods and Instruments for Solid Precipitation Measurement- Preliminary results -
R Nitu
Meteorological Service of Canada
AMS, Phoenix, AZ
12 Jan 2009
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Scope
• The WMO CIMO-XIV, has tasked the Expert Team on Surface-Based Instrument Intercomparisons and Calibration Methods to:
– assess the methods of measurement and observation of solid precipitation at automatic stations:
– 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.
• Goals of the survey:– The extent of using automatic instruments for measuring
precipitation (liquid and solid);– 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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Questions:
• How many stations use automatic precipitation gauges?
• How many stations use shields with such gauges as recommended by WMO? If so what type of shielding?
• How many stations use heated gauges?
• How many stations use other type of electronic sensors to measure precipitation, e.g. distrometers, snow pillows, etc?
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Survey Results
• By Dec 2008: – 53 Member countries responded to the 2008 CIMO
Questionnaire (46% of the global landmass) operate precipitation measurement programs using a combination of manual observations and automatic instruments:
▪ 41,187 stations,
▪ Average density: 1 station/1100 sq Km.
– 34 of the respondents (28% of the land mass) measure solid precipitation:
▪ 17,242 stations,
▪ Average density: 1 station/2200 sq Km.
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How many stations use automatic precipitation gauges?
• Measuring the amount of precipitation (41,187 stations, 53 countries):
– 82% of stations use manual means of observation;– 18% of stations use automatic instruments in 33 participating
Member countries.
• Measuring snow on the ground and snowfall (17,242 stations, 34 countries):
– 93% of stations use manual means of observation; – 7% of stations use automatic sensors.
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Automatic instruments in use
Amount of precipitation:
Weighing type gauges: measuring the mass accumulated in its bucket over a given period.
Tipping bucket type gauges: integrating over time the mass falling onto one of two small buckets in a tipping balance.
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Automatic instruments in use
Weighing Type Gauges:▪ used in 18 NMHSs,
▪ Six manufacturers (Geonor, OTT, Vaisala, MPS Systems, Meteoservis, and Belfort);
▪ Collecting area: 200, 400, 500 cm2
▪ Collecting capacity: 250 to 1000 mm
▪ Heating: optional (Geonor, OTT, Vaisala), standards feature (MPS Systems, Meteoservis)
Tipping Bucket Type Gauges:▪ Used in 22 countries;
▪ 28 different types of instruments from 21 manufacturers;
▪ The majority have heating circuits (funnel, collecting ring);
▪ Sensitivity: 0.1;0.2;0.25;0.5 mm of precipitation;
▪ Collecting area: 200 to 1000 cm2.
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How many stations use shields with gauges, as recommended by WMO? If so, what type of shielding?
• Overall, the automatic gauges:– 28% used with windshields
– 72% do not have windshields
• Weighing type gauges (WG):– 78% of WG use single wind shields
(Alter, Tretyakov, Nipher);– 22% of WG do not have wind
shields;
• Tipping Bucket type Gauges:– 30% configured with wind shields
(Japan, USA)– 1% configured with windshields in 6
other countries;– 69% do not have windshields
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Automatic Instruments for Solid Precipitation
• 13 participating countries use automatic instruments for snow on the ground and snowfall;
• 7% of sites reporting solid precipitation;
• Types of instruments: – sonic ranging sensors, – optical forward scatter
sensors;– snow pillow sensors.
• Sensors per site: 1-3;
SR-50:
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Next steps
• 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 for precipitation measurement of WMO Technical Commissions and Programs.
• Assess the need for an intercomparison of methods and equipment for automatic snowfall, snow depth, precipitation measurements.
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Intercomparison?
Potential Outcomes:• Relative performance of measurement of gauges in use.
• Efficiency and configuration 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.