Bucknell Weather Station  Information

Operation.
Once per minute, sensors measure temperature, relative humidity, wind speed and direction, and radiation (incoming and outgoing solar and far infrared). At the top of each hour, the datalogger calculates hourly mean values for these and several derived variables, measures atmospheric pressure, and stores the data in an output file (click here).






For full information on each sensor, click the link in "component" column below to download a technical manual (.pdf files).
Location
Lewisburg, PA
40°57'N 76°54'W
UTM 18N 340730E 453490N
Elevation 525' (160 m)

ariable/Function
Component
Range
Accuracy
Sensor
Temperature
HMP45C Temp/RH probe (mounting height: 2m)
-40°C to +60°C
±0.2°C at 20°C, ±0.4 at -20°C and 60°C
Platinum resistance Temperature (PRT) Detector
Relative Humidity
0-100%
at 20°C: ±2%RH (0 to 90%RH) ±3%RH (90 to 100%RH)
Vaisala HUMICAP 180 capacitive RH sensor
Precipitation
TE525WS Rain Gage
0 to 700mm/ hr
±1% up to 25 mm/hr
0 to -2.5% at 25-50mm/hr
0 to -3.5% at 50-75mm/hr
Tipping Bucket 
Barometric Pressure
CS105 Barometric Pressure Sensor
600-1060 mb
0.5mb at 20°C; ±2mb at -20°C to +45°C
Vaisala Barocap silicon capacitive pressure sensor
Wind Speed
Met One 034A-L Windset (mounting height: 3m)
0-49m/sec
for wind speed 
<10.1 m/sec = ±0.12m/sec ; 
>1m/sec = ±1.1% 
Cup anemometer
Wind direction
0-360°
±4°; resolution 0.5°
Vane driven potentiometer
Solar Radiation(incoming and outgoing)
Kipp & Zonen CNR1 Net Radiometer (mounting height: 3m)
0.3 to 3 micrometers
±10%  for daily sums
CM3 Pyranometers
Far Infrared Radiation(incoming and outgoing)
5 to 50 micrometers,
CG3 Pyrogeometers
Measurement and Control
Campbell Scientific CR10X datalogger
 Click here to access the datalogger control program.
Click here for the weather station wiring diagram
Support Structure
CS UT10 Tower (3m)
  

Notes on individual sensors and measurements:

Wind speed and direction. The station site meets the minimum criteria specified in the sensor technical manual. However, a row of evergreen trees to the west, topsoil and clean fill storage piles to the south, and buildings to the east of the station may affect wind measurements.


Radiation. The ground immediately west of the sensor is a tree nursery, and the presense of shrubs and small trees may affect radiation balances, particularly early and late in the day. The tower itself is a bright object that increases site reflectivity. Errors due to these factors may range from an estimated 1% to 10%. If needed for specialized research or teaching applications, the sensor can be temporarily relocated to a shorter mast up to 30 feet from the tower and on more level ground, eliminating these problems. Contact Professor Griffin in the Geography Department about proposed modifications.

Temperature and Relative Humidity. No special concerns.

Precipitation. Texas Instruments reports accuracy of 1% for rainfall intensities <25mm/hr. However, when precipitation is very light, the gage may not record any precipitation at all. Snow is not recorded until it melts. The gage is not heated, and can only store approx. 6 cm of snow, so frozen precipitation measurements are likely to be highly unreliable.

Currently, the rain gage is mounted on the tower, 3m above ground level. Updrafts may affect measured precipitation when wind speeds are high.