Each AZMET weather station is controlled by a Campbell Scientific Inc.
datalogger. From 1987 to 1992, the datalogger sampled the sensors every
60 seconds. From 1993 to present, the sampling rate is every 10 seconds.
At the end of each hour, the datalogger processes and stores all the
sampled measurements for that hour. Rain and solar measurements are
totalized. Soil temps are point measurements taken on the hour, and
all other readings are averaged from measurements during the hour.
An AZMET hour starts at one second after the hour and goes to the top
of the next hour. For example, the data listed for the 8:00 hour are
measurements from 7:00:01 to 8:00:00.
At midnight, the datalogger processes all the 10 second measurements,
picks out the daily maximums and minimums, and calculates the daily
averages, and totals. An AZMET day begins one second after midnight.
AZMET is on Arizona time; Mountain Standard Time.
Arizona does not adjust clocks for daylight savings time.
Below is a list of the sensors used at AZMET stations.
Once a year, we replace all the Solar sensors and Wind Speed sensors
with recalibrated sensors. Humidity sensor chips are replaced twice
a year. Other sensors are carefully monitored and checked during
each station visit.
Measurement Instrument Model Sensor Type Siting Accuracy
----------- ---------------- ----------- ------ --------
Air Temp. Vaisala Thermistor 1.5 m +/-0.4C
1992-Present HMP35C, HMP45C Fenwall Above
Air Temp. Camp. Sci. Model Thermistor 1.5 m +/-0.2C
1987-1995 207 Probe Fenwall Above
Rel. Humidity Vaisala Vaisala 1.5 m +/-2%RH
1992-Present HMP35C, HMP45C Capacitive Above
Rel. Humidity Camp. Sci. Model Resistance 1.5 m +/-5%RH
1987-1995 207 Probe Chip: Phys Above
Chem PCRC11 Surface
Soil Temp. Thermocouple Type 1 5,10 cm +/-0.2C
Solar Radiat. LiCor LI200 Silcon Cell 2.5m +/-5%
Pyranometer Pyranometer Above
Precipitation Sierra Misco Tipping Gage Top +/-1mm
RG2501 Rain Bucket With At ~43 cm
Gage Magnetic Above
Texas Electronics Tipping Gage Top +/-1mm
Model # TE525 Bucket With At ~43 cm
Rain Gage Magnetic Above
Reed Switch surface
Wind Speed Met One Model Anemometer 3.0 m +/-1.5%
014A Wind Speed Using Reed Above
Sensor Switch Surface
RM Young Anemometer 3.0 m +/-0.5 m/s
Wind Sentry Generating Above
Model 03101-5 AC Voltage Surface
Wind Direct. Met One Model Wind Vane 3.0 m +/-5 degrees
024A Wind Dir. Attached to Above
Sensor Potentiom. Surface
RM Young Wind Vane 3.0 m +/-5 degrees
Wind Sentry Attached to Above
Model 03301-5 Potentiom. Surface