Weather data has been collected at Toolik Lake by a Campbell 21x datalogger 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 99DLTLH.DAT, the three hourly data are in 99DLTLO.DAT, and daily summaries are in 99DLTLD.DAT. A second Campbell 21x datalogger 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 98DLTDAT.ZIP, which is archived at The Marine Biological Lab, Woods Hole, MA.

Notes: Wind Speed less than .447 is considered calm. Lake quantum stopped working in winter 1991 and was reinstalled just for the summer of 1998,1999. In August the Lake quantum sensor was not cleaned. Therefore the values are low. Quantum has an offset of -1.4 to -2.7. The data is not corrected. 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. Barometric pressure sensor was erratic for a few days in January for unknown reasons. Values were corrected. It was replaced 16Aug99. I August 1998 the tipping rain gage was fitted with a Campbell CS705 adapter for measuring snow. A Wyoming wind shield was build for the precipitation gage 30Aug99. See additional notes under Comments variable.

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

Sampling Description.

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