Class 1 · 100 m
Class 2 · 30 m
Class 3 · 10 m
Class 4 · 3 m
24 m · class 3
0 min
60 min
120 min
180 min
-10 °C
0 °C
10 °C
20 °C
30 °C
Logger · 1-min air temperature
76 flagged
SI kelvin · ITS-90
National metrology institute
Accredited laboratory
Field reference
Station sensor
U 0.040 °C
U 0.057 °C
U 0.101 °C
1 · Observed variable
2 · Purpose of observation
3 · Station/platform
4 · Environment
5 · Instruments and methods
6 · Sampling
7 · Data processing and reporting
8 · Data quality
9 · Ownership and data policy
10 · Contact
0 km
50 km
100 km
150 km
200 km
5 km
10 km
15 km
0.5° · 1.5 km
P
S
30 s · 100 sps
0 dbar
1,000 dbar
2,000 dbar
Ascent · 5.5 h
Drift · 10 day cycle
Class 1 · 100 m; Class 2 · 30 m; Class 3 · 10 m; Class 4 · 3 m
Sensors · Explainer
Interactive
An observation carries where it was made, how it was checked, what it traces back to and who can vouch for it. Seven steps from a weather station’s mast to a float two kilometres down.
01 · Siting
WMO-No. 8
WMO-No. 8 grades a site from class 1 to 5 for each variable. For air temperature it is the distance to heat sources such as buildings, car parks and water: class 1 beyond 100 m, then 30, 10 and 3 m. For wind it is distance in obstacle heights: 30, 10, 5 and 2.5 times. Classes 3 to 5 add up to 1, 2 and 5 °C of uncertainty to temperature.
Variable
02 · Quality control
Flags
The sensor feeds a logger that averages one-minute values; automatic checks flag each one before it travels. The range check rejects air temperatures outside −80 to +60 °C, the step check doubts a jump of more than 3 °C in a minute, and the persistence check doubts an hour that varies by less than 0.1 °C. Inject a fault and watch the flags.
Faults
03 · Traceability
GUM
Each calibration compares an instrument with a better one and adds its own uncertainty. Following the GUM, independent standard uncertainties combine as uc = √Σu², and the expanded uncertainty U = 2uc covers about 95 %. A display that reads in 0.1 °C steps alone contributes 0.1/√12. WMO-No. 8 asks for 0.1 K on air temperature.
Display resolution
Expanded uncertainty down the chain, k = 2
Lab reference
0.040 °C
+ bath
0.057 °C
Station sensor
0.101 °C
WMO-No. 8 target
0.100 °C
04 · WIGOS metadata
WMO-No. 1192
The WIGOS Metadata Standard describes an observation in ten categories, and a WIGOS station identifier names the station worldwide: series, issuer, issue number and local identifier, as 0-20000-0-71xxx for a station with a WMO number. Fill the categories this station reports.
Categories reported
Issuer of identifier
05 · Radar volume scan
VCP
A weather radar sweeps a stack of elevation angles every few minutes. Under standard refraction the beam rides an Earth of 4/3 its radius: h = √(r² + (kea)² + 2rkea sin θ) − kea. Far from the radar, the lowest tilt overshoots the weather near the ground and the beam widens as r·θ. Heights are stretched tenfold.
Radar
06 · Seismic vault
GNSS time
The P wave outruns the S wave, about 6 against 3.5 km/s in the crust, so the gap between them grows with distance: S − P = R(1/Vs − 1/Vp), about 8.4 km per second of gap. A GNSS receiver on the vault stamps every sample; any clock error moves the event by Vp × error.
Clock error
Samples per second
07 · Ocean profile
Argo
A profiling float changes its buoyancy with an oil bladder: it sinks to drift at 1,000 dbar, drops to its profile depth, then rises sampling temperature, salinity and pressure, and sends the profile by satellite before it sinks again. A decibar of pressure is close to a metre of depth.
Sample every
Cycle
An observation carries where it was made, how it was checked, what it traces back to and who can vouch for it. Seven steps from a weather station’s mast to a float two kilometres down.
WMO-No. 8 grades a site from class 1 to 5 for each variable. For air temperature it is the distance to heat sources such as buildings, car parks and water: class 1 beyond 100 m, then 30, 10 and 3 m. For wind it is distance in obstacle heights: 30, 10, 5 and 2.5 times. Classes 3 to 5 add up to 1, 2 and 5 °C of uncertainty to temperature.
The sensor feeds a logger that averages one-minute values; automatic checks flag each one before it travels. The range check rejects air temperatures outside −80 to +60 °C, the step check doubts a jump of more than 3 °C in a minute, and the persistence check doubts an hour that varies by less than 0.1 °C. Inject a fault and watch the flags.
Each calibration compares an instrument with a better one and adds its own uncertainty. Following the GUM, independent standard uncertainties combine as uc = √Σu², and the expanded uncertainty U = 2uc covers about 95 %. A display that reads in 0.1 °C steps alone contributes 0.1/√12. WMO-No. 8 asks for 0.1 K on air temperature.
The WIGOS Metadata Standard describes an observation in ten categories, and a WIGOS station identifier names the station worldwide: series, issuer, issue number and local identifier, as 0-20000-0-71xxx for a station with a WMO number. Fill the categories this station reports.
A weather radar sweeps a stack of elevation angles every few minutes. Under standard refraction the beam rides an Earth of 4/3 its radius: h = √(r² + (kea)² + 2rkea sin θ) − kea. Far from the radar, the lowest tilt overshoots the weather near the ground and the beam widens as r·θ. Heights are stretched tenfold.
The P wave outruns the S wave, about 6 against 3.5 km/s in the crust, so the gap between them grows with distance: S − P = R(1/Vs − 1/Vp), about 8.4 km per second of gap. A GNSS receiver on the vault stamps every sample; any clock error moves the event by Vp × error.
A profiling float changes its buoyancy with an oil bladder: it sinks to drift at 1,000 dbar, drops to its profile depth, then rises sampling temperature, salinity and pressure, and sends the profile by satellite before it sinks again. A decibar of pressure is close to a metre of depth.
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