Transcript Handbook on Meteorological Observations Henk Benschop, Jitze van der Meulen Royal Netherlands Meteorological Institute.

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

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
6-11-2015
TECO 2005
2
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.
6-11-2015
TECO 2005
3
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
6-11-2015
TECO 2005
4
Handbook
on Observations
6-11-2015
TECO 2005
5
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
6-11-2015
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
TECO 2005
6
Contents
1.
Description
1.1
1.2
1.3
1.4
1.5
name of variable (e.g.. wind, precipitation)
definitions
units: standard cf. SI (e.g. m/s), or non-standard (e.g kts.)
derived variables (e.g. wind speed, -direction) + definition
codes and explanations (synop, metar)
2.
2.1
2.2
2.3
2.4
2.5
Operational requirements
range, e.g. 0 - 50 m/s
resolution, e.g. 0.1 ° C
required accuracy, e.g. ± 0.5 hPa
required frequency of observations, e.g. every 12 s
required availability per specific period, e.g. 50 %
6-11-2015
TECO 2005
7
Contents (cont.)
3. Instruments and techniques
3.1 technical specifications of the instruments
3.2 management, maintenance and calibration procedures
4.
4.1
4.2
4.3
Procedures
procedures in case of missing data
procedures for data validation
procedures for control of observation sites (inspection)
6-11-2015
TECO 2005
8
Contents (cont.)
5. Calculation of other parameters
e.g. formula for reduction to MSL pressure, formula
for calculating dew point from U and air-t
6. Siting, requirements with respect to surroundings
6.1 Specific conditions per instrument
6.2 Conditions with respect to the surroundings of the site
6-11-2015
TECO 2005
9
Station lay-out
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)
6-11-2015
TECO 2005
10
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
6-11-2015
TECO 2005
11
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.)

6-11-2015
TECO 2005
12
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;
6-11-2015
TECO 2005
13
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.)
6-11-2015
TECO 2005
14
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)
6-11-2015
TECO 2005
15
Version management
To keep it up-to-date
Yearly updates:
• procedure for updating text, figures, formulas
• list of recipients
• chapter ‘ownership’
6-11-2015
TECO 2005
16
6-11-2015
TECO 2005
17