Handbook on Meteorological Observations
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Transcript of Handbook on Meteorological Observations
Handbook onMeteorological Observations
Henk Benschop, Jitze van der Meulen
Royal Netherlands Meteorological Institute
04/19/23 TECO 2005 2
BackgroundThe National Meteorological Authority should provide a Manual (or Guide) with Standard procedures on:
definitions of the variables to be observed functional specifications of each variable Recommended observation technology (standards) Siting and exposure of instruments Station inspection Data acquisition and data processing
(computation) Data presentation (code formats) Data validation and archive
04/19/23 TECO 2005 3
Problem Many guides are available on instrument
measurement, data processing and presentation and on weather information services- e.g. CIMO Guide, Manuals on GOS, GDPS, Codes, etc.
But no integral standard manual in which the national standards are stated to provide the data service from OBS to INFO.
04/19/23 TECO 2005 4
Objectives Definitions, units, coding, derived variables Requirements on range, resolution, measurement
uncertainty, frequency of measurements, etc. Instruments and technical specifications, calibration
procedures Procedures in case of missing data, methods for data
validation, procedures on site inspection Calculation of parameters, formulae to reduce data;
encoding siting and exposure criteria Inspection criteria Considerations with respect to the surroundings
04/19/23 TECO 2005 5
Handbookon Observations
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Structure in line with CIMO Guide1. General2. Temperature3. Atmospheric pressure4. Humidity5. Wind6. Precipitation7. Radiation8. Sunshine duration 9. Visibility 10. Evaporation 11. Soil temperature
12. Upper air pressure, temperature, humidity
13. Upper air wind 14. Present weather,
past weather, state of the ground
15. Observation of clouds
16. Ozone measurement17. Atmospheric
composition18. Seawater temperature19. Ocean waves 20. Lightning
04/19/23 TECO 2005 7
1. Description1.1 name of variable (e.g.. wind, precipitation) 1.2 definitions 1.3 units: standard cf. SI (e.g. m/s), or non-standard (e.g kts.) 1.4 derived variables (e.g. wind speed, -direction) + definition 1.5 codes and explanations (synop, metar)
Contents
2. Operational requirements2.1 range, e.g. 0 - 50 m/s 2.2 resolution, e.g. 0.1 ° C 2.3 required accuracy, e.g. ± 0.5 hPa 2.4 required frequency of observations, e.g. every 12 s2.5 required availability per specific period, e.g. 50 %
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3. Instruments and techniques 3.1 technical specifications of the instruments 3.2 management, maintenance and calibration procedures
Contents (cont.)
4. Procedures4.1 procedures in case of missing data 4.2 procedures for data validation 4.3 procedures for control of observation sites (inspection)
04/19/23 TECO 2005 9
Contents (cont.)
5. Calculation of other parameterse.g. formula for reduction to MSL pressure, formula for calculating dew point from U and air-t
6. Siting, requirements with respect to surroundings6.1 Specific conditions per instrument 6.2 Conditions with respect to the surroundings of the site
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A. Temperature_1.50m(C) B. Relative_humidity_1.50m(%) C. Global Radiation(Joule/cm2) D. Temperature 10cm(C) E. Visibility F. Sum of precipitation(mm) G. Duration of precipitation(hr) H. Wind speed(m/s) I. Wind direction(degrees) J. Atmospheric pressure (hectoPascal)
Station lay-out
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Instrument description• E.g. cup anemometer
steel-cup .
A sensor is built into the mechanism the reacts to a signal from the rotating spindle every revolution. Registration of the rotation rate, which is near enough proportional to the prevailing wind speed, is done using a pulse counter. The number of pulses per unit time (e.g. per second) is counted and the speed of rotation is derived from this.
drum with slots
optical sensor with photo cell
04/19/23 TECO 2005 12
Codes (SYNOP, METAR, CLIMAT) Full explanation of codes, e.g. code fxfx:
group 910ff: the maximum wind gust in m/s in the 10 minutes preceding the moment of observation {i.e. exactly 5 minutes before every whole hour (UTC)} where this is 5 m/s or more greater than the synchronous value of ff in section 1.
(etc.)
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Validation
E.g. FX FX must be FH, otherwise suspect; FX must be FF, otherwise suspect; abs[FXh - (-1/6 (FXh-2+FXh+2) + 2/3 (FXh-
1+FXh+1))] must be 8 knots, otherwise FX is suspect;
FX must be 80 knots, otherwise suspect;
04/19/23 TECO 2005 14
Station inspection procedures
Every wind measurement site that has an operational function within the KNMI observation network is inspected on average twice annually by an official from WM/OD/station management. Extra interim inspections can also be carried out on request
The inspection can cover the following checks (example):d) Comparison of the instantaneous (12") wind speed value measured by the sensor with the instantaneous wind speed value as read off from a reference ...(etc.)
04/19/23 TECO 2005 15
Publication
Strategy: all open to the public (through national meteor. library)
• hard copy book, with replaceable loose leaves, yearly updated
• electronic versions available on WWW
http://www.knmi.nl/onderzk/applied/ob/nl/ob_handboek.html (Dutch)
http://www.dwd.de/EUMETNET/Berichte/Handbuch_NL.doc (English)
04/19/23 TECO 2005 16
Version management
Yearly updates:• procedure for updating text, figures, formulas• list of recipients• chapter ‘ownership’
To keep it up-to-date
04/19/23 TECO 2005 17