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 Imnavait weather station,12 kilometers away and 200 meters higher, is also used to fill in data gaps. Regressions of summer air temperature between Imnavait and with Toolik are good but during the winter months there is greater variability. This station is maintained by Larry Hinzman and Doug Kane, Water Research Center; University of Alaska Fairbanks; Fairbanks, AK 99775-5860. Precipitation data from the Natural Resources Conservation Service (NRCS) Alaska Imnavait weather station is also used to fill in the data gaps. Please contact Rick McClure, Data Collection Officer, Natural Resources Conservation Service, 949 E. 36th Ave., Suite 400,, Anchorage, AK 99508-4362, (907) 271-2424 for more details.
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: Campbell CS500 temperature/RH sensors were problematic. The splice in the lead Moisture infiltrated the lead wire splice joint and caused a short resulting in bad readings and in the worst case it affected other sensors on the data logger. Backup air temperature/RH and radiation sensors were used to estimate the 5-meter air and temperature/RH sensor and the radiation sensors. Wind speed less than .447 is considered calm.
Radiation data were not totaled for the winter months since no attempt was made to keep sensors snow and frost-free.

Lake temperature is measured at the lake depth sensor. Therefore the lake depth measurements give the depth at which lake temperature is measured.

See additional notes under Comments