Hourly weather data from the Arctic Tundra LTER site at Toolik Lake. The following parameters are measured every minute and averaged or totaled every hour: 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 precipitation.
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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 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 98DLTLH.DAT, the three hourly data are in 98DLTLO.DAT, and daily summaries are in 98DLTLD.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 speeds less than .447 are considered calm. The precipitation tipping rain bucket has an Alter type wind screen. In the fall of 1998 a Campbell CS705 Snowfall adapter was added for snowfall measurements. Air temperatures are measured with Campbell 207 sensors and type T thermocouple wire. The difference between the Campbell (Air Temp 1M and Air Temp 5M) and thermocouple measurements (Air TC 1M and Air TC 5M) is about +- 0.5 Celsius with a slightly greater difference at temperatures below - 40. The Campbell 207s were not corrected at temperatures below -40. Lake quantum stopped working in winter 1991 and was reinstalled just for summer months starting 1998. The quantum sensor has an offset of about -1.8. During the winter months there were some abnormal barometric pressure values which were deleted. 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. 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
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))
TOTAL J CM2 HR: PYRANOMETER * 0.3600 jcm2 * 1000 Watt/Kwatt
Log of changes:
17June98 Added winter data and error checked. JL
For Archival Use:
DATE RECEIVED: Aug 1998, June 1999
DATA FILE ENTERED BY: Jim Laundre
DATA FILE VALIDATION:
NAME: Jim Laundre
Version 3: Metadata updated to newer form (with sites sheet). Units updated to current standards. Discrepancy with variable names fixed. CH April 2013.
Version 4: Corrected Distrubution URL. It had xlsfiles in the path. Jim L 19Jun14
Version 5: Changed Distrubution URL since the LTER network DAS system is being discontinued. JimL 9Apr2015
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