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Handbook on Meteorological Observations. Henk Benschop , Jitze van der Meulen Royal Netherlands Meteorological Institute. Background. The National Meteorological Authority should provide a Manual (or Guide) with Standard procedures on: definitions of the variables to be observed

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Handbook on meteorological observations

Handbook onMeteorological Observations

Henk Benschop, Jitze van der Meulen

Royal Netherlands Meteorological Institute


Background
Background

The 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

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Problem
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.

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Objectives
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

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Handbookon Observations

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Structure in line with cimo guide

1. General

2. Temperature

3. Atmospheric pressure

4. Humidity

5. Wind

6. Precipitation

7. Radiation

8. 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 measurement

17. Atmospheric composition

18. Seawater temperature

19. Ocean waves

20. Lightning

Structure in line with CIMO Guide

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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. Procedures

4.1 procedures in case of missing data 4.2 procedures for data validation 4.3 procedures for  control of observation sites (inspection)

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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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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

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    Codes synop metar climat
    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
    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;

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    Station inspection
    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.)

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    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)

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    Version management

    To keep it up-to-date

    • Yearly updates:

    • procedure for updating text, figures, formulas

    • list of recipients

    • chapter ‘ownership’

    TECO 2005



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