Experimental Design/Sampling Description:
A Campbell 21x data logger has collected weather data at Toolik Lake since June 1988. Sensors that are measured every minute and averaged or totaled every hour include: air temperature and relative humidity at 1 and 5 meters, wind speed at 1 and 5 meters, wind direction at 5 meters, global solar radiation, photosynthetically active radiation, barometric pressure, and unfrozen precipitation. Sensors measured every 10 minutes and averaged every three hours include, soil temperatures, lake temperature, lake depth, and evaporation pan depth and pan water temperature. Net radiation and pan evaporation are only measured during the summer months. The hourly data are in the file yyyyDLTLH.DAT, the three hourly data are in yyyyDLTLO.DAT, and daily summaries are in yyyyDLTLD.DAT. A second Campbell 21x data logger about 700 meters from the main weather station logs air and soil temperatures and photosynthetically active radiation in the experimental treatment plots. Treatments include greenhouse, shading, and fertilization. In the control plot wind speed and direction, global solar radiation and unfrozen precipitation are also measured. This station is also used as a backup to the main weather station. The full description of the sensors and site is in file SENSORS.DOC. The original data is in file yyyyDLTDAT.ZIP, which is archived at The Marine Biological Lab, Woods Hole, MA.

Notes and Comments:
High winds Nov 2003 caused the logger to skip two hours and the solar changer to fail. Logging stopped on Jan 2004 when the battery voltage dropped below 9 volts. In addition the Onset Computer Hobo loggers that are used as a backup stopped logging on Nov . Most likely caused by static electricity build up.

Wind Speeds less than .447 are considered calm. For the global solar radiation and photosynthetically active radiation sensors no attempt is made to correct for frost or snow on the sensors during the winter months. Therefore winter radiation data should be view as suspect and used only qualitatively. August 1998 the tipping rain gage was fitted with a Campbell CS705 adapter for measuring snow. A Wyoming windshield was build for the precipitation gage 30Aug99.

See additional notes under Comments variable.

CALCULATIONS
variable Formula
DAYS : JULIAN + (HOUR/2400)
VAPOR PRESS 5M: If Air Temp > 0 then (RH 5M/100) * 6.1121 *
exp(17.368 * AIR TEMP 5M/(238.88 + AIR TEMP 5M))
If Air Temp < 0 then (RH 5M/100) * 6.1121 *
exp(17.966 * AIR TEMP 5M/(238.88 + AIR TEMP 5M)) (Buck 1981).
TOTAL J CM2 HR: PYRANOMETER * 0.3600 jcm2 * 1000 Watt/Kwatt

REFERENCES: Buck, A.L.. 1981 New equations for computing vapor pressure and enhancement factor. Journal of Applied Meteorology 20:1527-1532.