ISO 17714:2007

Overview

ISO 17714:2007 - Meteorology: Air temperature measurements - Test methods for comparing the performance of thermometer shields/screens and defining important characteristics - defines how to characterise and test thermometer shields (screens) used to protect temperature sensors from radiation, precipitation and accidental damage. The standard applies only to air temperature measurements (not humidity) and covers both naturally ventilated and artificially ventilated (aspirated) screens. It establishes test procedures to inter-compare screen designs and to quantify measurement biases such as solar radiation errors.

Key topics and technical requirements

• Scope: Tests and characteristics specific to temperature measurement screens; both natural and artificial ventilation considered.
• Defined terms: aspiration rate, internal ventilation factor, representative height, screen reference point, solar radiation errors, system response time.
• Field test conditions:
  • Test sites must represent expected meteorological conditions (radiation, wind, snow, fog, etc.).
  • Screens installed on level, homogeneous ground; minimum 30 m from heat sources; separation between screens ≥ 3 m.
  • Representative measurement height typically 1.25–2 m (±5 % tolerance).
• Instrumentation & performance:
  • Use matched thermometers with similar response times (WMO recommends ~30 s); measurement uncertainty ≤ 0.2 K.
  • Data sampling: averages over 1-minute periods with at least 6 samples/minute; wind data ≥ 1 Hz.
• Measured variables: horizontal global solar radiation, wind speed/direction at representative height and at 10 m, relative humidity, cloud cover, precipitation occurrence/type, surface albedo, sun azimuth/elevation.
• Test methods & analyses: comparability analysis, global temperature analysis, extreme-value analysis, statistical analysis of radiation error, influence of surface albedo, selection of typical conditions.
• Screen characteristics to measure: aspiration rate, internal ventilation factor, representative height/reference point, and system response time (response defined at external wind speed 1 m·s⁻¹).

Applications and who uses it

ISO 17714:2007 is practical for:

• National meteorological services and weather station operators ensuring comparable and accurate air temperature records.
• Instrument and thermometer shield (screen) manufacturers validating and improving designs.
• Climate researchers and environmental monitoring networks needing standardized intercomparison methods.
• Regulatory bodies and standards organizations adopting measurement best practices.

Use cases include performance benchmarking of new shield designs, site acceptance testing, and improving climatological data quality by reducing radiation-induced temperature biases.

Related standards

• WMO No. 8 (screen best practices and siting guidance)
• IEC 60751 (platinum resistance thermometers) and ASTM E644 (thermistors) - referenced for thermometer examples and calibration guidance.

Keywords: ISO 17714:2007, thermometer shield, thermometer screen, air temperature measurements, radiation error, aspiration rate, system response time, meteorology, weather stations.