In 1990 a data logger and sensors were installed at block 2 of the Moist Acidic Tundra (MAT) site at Toolik Field Station Long Term Ecological Research Site (LTER). These have been used since to monitor weather and soil temperatures. Please see temperature soil files for soil temperature information .
Climatic conditions were measured in plots covered by green houses, shade coverage and control non-disturbed plots.
For sensor and column labels CT = Control, GH = Greenhouse and SH = shade house. Note that shade cloth and plastic greenhouse material are attached to a permanent frame structure every spring (early to mid June) and removed in late August each year. Thus temperature measurements in the control plot may be representative of all three sites when the covers are not present.
Sensors in the control plot include: global solar radiation, photosynthetic active radiation, unfrozen precipitation, air temperature, relative humidity, wind speed, and wind direction at 3 meters. Additional seasons in greenhouses and shade houses plots measure air temperature, relative humidity and photosynthetic active radiation during the growing season. These sensors are read every minute and averaged or totaled every hour. Hourly and daily summaries are in files yyyy-yyyy_SiteCode_WeatherHourly and yyyy-yyyy_SiteCode_WeatherDaily respectively, where yy is the year in which the data are collected. The original data is archived at The Marine Biological Lab, Woods Hole, MA.  NOTES: -The covers on greenhouses and shade houses are removed every fall and reinstalled every spring as described above.-Only unfrozen precipitation is reported.-Soil temperatures are problematic since frost heaving of the probes caused depth of measurements to change. -For the global solar radiation and photosynthetic 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.

CALCULATIONS:
DAYS: JULIAN + (HOUR/2400)
PYR TOTAL CM2 HOUR: PYRANOMETER * 0.3600 jcm2 * 1000 Watt/Kwatt NOTE: Control PAR (CQUANT )sensor reads - 50 when in the dark. Sensor errors, erroneous data and values outside the instrument range are indicated by #N/A. Due to changes in sensor locations over time '.' have been added in years where sensors were not present. Prior to 1995 some sensors had duplicates where one was placed in the north end of the plot (indicated by N) and the other in the South (S). From 1995 onward these were replaced with a single sensor in the center of the plot. The columns for N & S were continued in later years despite no data to ease with analysis if multiple years were to be compared.  -----------------------------------------------------------------------------------------------------------------------------------------------Sensor DescriptionFollowing are brief descriptions of the sensors used at the weather monitoring station. Included with each description is a list of stations using the sensor and the number of sensors at that site. Company addresses follow the list. ---------------------------------------------------------------------------------------------------------------------------------------------PYRANOMETER:Li-Cor, Pyranometer: Model LI-200SA- Sensor measures global solar radiation (sun plus sky). Specs: Sensitivity - 80mA per 1000 Watts m-2. Absolute error max ±5% but typically ±3QUANTUM:Li-Cor, Quantum. Model LI-190SB. Quantum measure photosynthetically active radiation (PAR) in mmol s-1 m-2. Specs: range 400-700nm wavelength. Sensitivity 8mA/1000 mmol s-1 m-2. Relative error less then ±10% for plant canopies or less then ±5% for growth chambers. Toolik.RELATIVE HUMIDITY/TEMPERATURE:Campbell Scientific, CS500 Temperature and Relative Humidity Probe. Uses PRT for temperature measurement; capacitive RH chip for RH. Accuracy is ±3% over 10-90% RH; ±6% over 90-100% RH. Manufactured by Vaisala, Inc.WIND DIRECTION:MET-ONE, (supplied by Campbell Scientific) Wind direction use a light weight, air foil vane and a potentiometer to produce an output that varies proportional with wind direction. Specs: Minimum Wind speed to get accurate reading = 1.0 mph. Accuracy ±5° Temperature range -50 to 70°C.WIND SPEED:MET-ONE, (supplied by Campbell Scientific) Wind speed sensor Model 014A. Sensor uses a 3-cup anemometer assembly and simple magnet-read switch assembly to produce a series of contact closures whose frequency is proportional to wind speed. Specs: Operating Range - 0 to 125 mph or 0-60 m/s. Accuracy ±1.5% or 0.25 mph. Working temperature range - -50 to 85°CRAIN GAUGE:Texas Electronics, Inc. (supplied by Campbell Scientific) Tipping Bucket Electric Rain Gauge. A complex spun collector funnel with a knife edge that diverts the water to a tipping bucket mechanism. For each tip a magnet causes an electronic pulse that is recorded. Each alternate tip occurs for each 0.01 inch of rainfall. Specs: Accuracy 1% at 2 inches/hr or less. Accurate Temperature Range: 0 - 37°C. Alter wind shield installed around gauge.THERMOCOUPLES:Omega Engineering, Copper-Constantan wire. Range -200 to 350 °C. Limits of error: Standard wire 1.0°C or 0.75% above 0°C and 1.0°C or 1.5% below 0°C. Special wire 0.5°C or 0.4%.List of manufactories and suppliers.Campbell Scientific, Inc.81 W. 1800 N.Logan, Utah 84321-1784(435)750-1739Li-Cor : 4421 Superior St, P.O. Box 4425, Lincoln, Nebraska 68504 (800)447-3576Omega Engineering, Inc. P.O. Box 4047, Stamford, CT 06907-0047 (800)826-6342 Reference Citations: Buck, A.L. 1981 New equations for computing vapor pressure and enhancement factor. Journal of Applied Meteorology 20:1527-1532.