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 3 and 5 meters, wind speed at 3 and 5 meters, wind direction at 5 meters, global solar radiation, photosynthetically active radiation, barometric pressure, and unfrozen precipitation.
Data set ID:
EML revision ID:
Experimental Design/Sampling Description:
The Arctic LTER 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:
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 August 2006 the tipping rain gage was fitted with a Campbell CS705 adapter for measuring snow. A Wyoming windshield was build for the precipitation gage 30Aug99. In August 2006 a OTT Pluvio Precipitation Gauge. (Standard with a heating ring. Resolution: 0.01/0.1; Collecting area 200 cm2; Total quantity 250 mm) replaced the tipping rain gauge/CS705 adapter.
On 12June2006 replace the Vaisala barometer with a Setra 278 Barometric Pressure Sensor. Changed Barometric output from mmHg to millibar for all of 2006 to present .
The Temperature /RH sensor (CampbellCS500) only records to -39 C and there is greater error below -35 C. The Thermocouples(TC) are used to correct for temperatures below -35 C. A regression is used since the TC are slightly different.
In October 2007 the program was changed to correct the reference temperature for measuring thermocouples. A polynomial was fitted against the output temperatures vs. real temperatures for temperatures below zero. See Campbell 107 manual. A subroutine is used to apply the polynomial when temperatures are below 0 C.
On August 19-20, 2008 - the weather station underwent an upgrade to the main data logger to a Campbell CR3000. Wind speed at 1 m was removed; Wind speed at 5m was replaced Vaisala HMP45C. Pyranometer was replaced w/ Kipp and Zonen CMP6 (ventilation unit - year round numbers are now available). Temperature/RH at 1 m was removed and replaced w/ an RMYoung T/RH probe at 3 m.
There appears to be an offset between the Vaisala at 5 meters and the RMYoung Temperature at 3 meters. This still needs more testing.
All wind directions after August 19th were deleted. There was programming error where the wind direction was only sampled once an hour. This was not corrected until summer 2010.
Wind speeds from Moist acidic station could be used instead.
Additional comments from J. Cherry:
Wind speed data from Jan 1, 2009-April 19, 2009 is suspect.
Winter precipitation (precip when temp < approx. 1 C) is always suspect. False precipitation events are common in winter. Data Delete
Program change to correctly calculate the wind vector. Previously the program statement had wind speed entered twice instead of wind speed and wind direction. Jim L
Reprogrammed the barometric pressure to a double storage to increase precision.
Corrected rain_mm since the program is assuming the tip = .01 mm but it is .1mm
See additional notes under Comments variable.
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
Updated Metadata sheet
Version 2: Corrected Distrubution URL. It had xlsfiles in the path. Jim L 19Jun14
Version 3: Changed Distrubution URL since the LTER network DAS system is being discontinued. JimL 9Apr2015
Download a comma delimited (csv) or Excel file (includes metadata and data sheets).
Use of the data requires acceptance of the data use policy --> Arctic LTER Data Use Policy
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