Weather data has been collected at Toolik Lake (68 degrees 38'N, 149 degrees 36'W) 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, net radiation (Fritschen type), 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 89DLTLH.DAT, the three hourly data are in 89DLTLO.DAT, and daily summaries are in 89DLTLD.DAT. Data in the field are stored on a Campbell SM716 storage module (capacity of 358,000 data points ). In the summer a direct line from the datalogger to a computer allows data to be viewed and collected daily. 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 89DLTDAT.ZIP which is archived at The Marine Biological Lab, Woods Hole, MA.

Notes: Wind speed less than .447 is considered calm. A number of sensors were unhooked for the winter months. Changed AIR TEMP 5M < -40 C to the value of AIR TC 1M. Thermister at 5 meters is only good to -40 C. Temperature data from Kane and Hinzman's Imnavait weather station included and and used to fill in some missing data. Since the Imnavait station is about 200 meters higher in elevation and 12 km east, regression equations were developed using data from before and after missing data. The precipitation tipping rain bucket has an Alter type wind screen. 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. 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.

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 HOUR: PYRANOMETER * .3600 jcm2 * 1000 watt/Kwatt

Imnavait data collected by Larry Hinzman and Doug Kane Water Research Center; University of Alaska Fairbanks Fairbanks, AK 99775-5860