Mesonet | Air Temperature and Related Measurements

TAIR

The 5-minute average air temperature at a height of 1.5 meters above the ground.

This sensor is quite rugged and accurate. Prior to 2009, the sensor was housed in a naturally-ventilated radiation shield. Such shields can create temperature errors of several degrees Celsius when the wind is calm (less than 1 m/sec) and solar radiation is high.
Since 2009, the sensor is housed in an aspirated radiation shield, which continuously draws ambient air over the sensor, while protecting it from solar radiation.

Type	Sensor Used	Standards Units	Accuracy
Standard - Primary	RM Young 41342 Platinum RTD Probe 2017-Present; Thermometrics Air Temperature 2004-2017; PDF Vaisala HMP35C 1994-2003	degrees Celsius	± 0.5 °C

RM Young 41342 Platinum RTD

Same sensor as TAIR but positioned at 9 meters above ground level.

This thermistor uses an unaspirated radiation shield, resulting in readings with a warm bias on calm, sunny days.

Type	Sensor Used	Standards Units	Accuracy
Standard - Secondary	RM Young Platinum RTD Probe 2015-Present; Thermometrics Air Temperature, PDF; 1994-2015	degrees Celsius	± 0.5 °C when windspeed is > 6 m/s
			± 1.0 °C when windspeed is 3 - 6 m/s
			± 1.5 °C when windspeed is 2 - 3 m/s
			±3.0°C when windspeed is 1 - 2 m/s

RM Young 41342 Platinum RTD

Not measured, but computed from the 1.5 meter air temperature and relative humidity.

The heat index is used to provide information about possible heat stress on the human body.

Sensor Used	Standard Units
Thermometrics Air Temperature (for Air Temperature), PDF	degrees Celsius
Vaisala HMP45C (for Relative Humidity), PDF

Not measured, but computed from the 1.5 meter air temperature and the wind speed at 10 meters.

Wind chill represents the cooling effect on the human body of low temperatures combined with wind.

Sensor Used	Standard Units
Thermometrics Air Temperature (for Air Temperature), PDF	degrees Celsius
RM Young Wind Monitor (for Wind Speed), PDF