Station Site Description and Equipment Overview
Station Topography Description: Our goal was to select permanent station sites that meet strict criteria so they represent the general climate of the surrounding area. Higher landscape positions were chosen to avoid low lying areas prone to cold air drainage or other microclimatic influences. Steeply sloping sites were avoided if possible because they sometimes produce reverse or erratic wind directions. Most stations are located in the open, at least 20 to 25 times the height of an obstruction away from it, where winds are minimally affected. With these provisions, we assume that each station adequately represents all weather conditions, except rainfall, in a 20 mi. (32 km) radius circle. Rainfall is extremely variable, even over short distances, because it is usually produced by thunderstorms.
Site Description: The station's site area is about 20 by 25 feet and is fenced if necessary. Our goal is to maintain grass cover in the area, except for a 4- to 5-foot square area that is kept bare for soil temperature measurement.
Equipment and Sensor Overview: The majority of the sites consist of a Campbell Scientific, Inc. 10-meter (30 ft) tall steel tripod. The tripods are equipped with a Wind Monitor HD to measure wind speed and direction. It is mounted on the north side of a cross arm located at 3 meters (10 ft). An SP-110 pyranometer is mounted on the south side of the same crossbar, and a Vaisala HMP temperature/humidity sensor is located in a gill shield mounted directly on the tripod at 1.5 meters (5 ft). A tipping bucket rain gauge is located approximately 3 meters (10 ft) from the tripod. It is attached to a steel pipe 75 centimeters (30 in) from the soil surface.
Select sites also have a 3-meter (10 ft) tower purchased from Campbell Scientific, Inc. (model UT30) which is cemented into the ground. These sites include the traditional wind sensors (mounted at 3 meters (10 ft) as well as the standard temperature sensors at 1.5 meters (5 ft). In addition, these sites have a second Wind Monitor HD wind speed and direction sensor mounted at 10 meters (33 ft) and a second Vaisala temperature/relative humidity sensor located at 9 meters (30 ft).
A weatherproof enclosure is attached to the north side of the tower or tripod. A solar panel is mounted to the south side of all 3-meter (10 ft) tripod stations with most 10-meter (33 ft) tower sites having a solar panel mounted on a separate pole. The enclosure contains a Campbell Scientific, Inc. CR-1000 datalogger, Sierra Wireless Raven XT or Raven RV50 wireless modem, one or two batteries, and a voltage regulator. All stations are accessed by wireless modem only. Barometers are housed inside the enclosures at 33 stations. Soil temperatures at the 10-centimeter (4 inch) depth are measured with copper-constantan thermocouples.
Select sites also have deep soil temperatures ranging from 5 to 225 centimeters (2 to 88 in) in depth and/or soil moisture sensors ranging from 10 to 100 centimeter (4 to 40 in) in depth. Deep soil temperatures are measured using copper-constantan thermocouples. Volumetric water content is measured using Campbell Scientific, Inc., CS655 Soil Water Content Reflectometers.
Equipment List
Barometer - Vaisala - Model PTA-427
NDAWN measures barometric pressure at 70 centimeters (2 ft) above the soil surface. One measurement is taken every 15 minutes, beginning at the top of the hour. The pressure value recorded at the top of the hour is the one archived. For more details, see the PTA-427 Barometric Pressure Transducer Operator's Manual printed by Campbell Scientific, Inc.
Datalogger - Campbell Scientific, Inc. - CR1000
Dataloggers are a data acquisition system that provides sensor measurement, time keeping, data reduction, data/program storage and control functions. For more details, see CR1000 Measurement and Control System Operators Manual printed by Campbell Scientific, Inc.
Cellular Communication Modem - Sierra Wireless - AirLink Raven XT or AirLink Raven RV50
Cell modems provide contact between the computer and datalogger across a wireless communication system. The wireless modem allows stations to be accessed frequently and display data online every 5 minutes. For more details, see the AirLink Raven XT User Guide or AirLink Series RV User Guide printed by Sierra Wireless.
Multiplexer - Campbell Scientific, Inc. - AM416 - AM16/32B
NDAWN uses multiplexers at 12 stations where deep soil temperatures are measured. This device increases the number of sensors that may be scanned by the datalogger. For more details, see the AM416 Relay Multiplexer Instruction Manual and AM16/32B Relay Multiplexer Instruction Manual printed by Campbell Scientific, Inc.
The pyranometer measures incoming solar radiation. NDAWN measures solar radiation 2.7 meters (9 ft) above the soil surface at the majority of stations. For more details, see the Pyranometer SP-110 Owner's Manual printed by Apogee Instruments.
Rain Gauge - Texas Electronics - TR-525I
NDAWN measures rainfall (inches) at approximately 1 meter (3 ft) above the soil surface. The rain gauge uses a tipping bucket system that measures .254 millimeters (0.01 in) with each bucket "tip". The rain gauges do not measure snowfall. An 'M' indicates a missing value. An 'E' indicates data have been estimated from surrounding stations. Estimated rainfall amounts are always suspect because of the large spatial variation in rainfall. Users should evaluate estimated data for their applications. For more details, see the TE525 Tipping Bucket Rain Gage Instruction Manual printed by Campbell Scientific Inc.
Solar Panel - Campbell Scientific, Inc. - SP20, SP10, and Ameresco, Inc. - BSP30-12, 90J-12
The solar panel recharges the battery during the daylight hours. For more details, see the SP10, SP10R, SP20, and SP20R Solar Panels Instruction Manual printed by Campbell Scientific, Inc. or the BSP Panel Series - 30W Solar Panel data sheet printed by Ameresco, Inc.
Soil Temperature - Thermocouple
The Type T (copper-constantan) thermocouple measures bare soil temperatures and turf soil temperatures at a 10-centimeter (4 in) depth, as well as deep soil temperature's at 5 centimeters (2 in), 10 centimeters (4 in), 20 centimeters (8 in), 30 centimeters (11 in), 40 centimeters (16 in), 50 centimeters (20 in), 60 centimeters (24 in), 80 centimeters (31 in), 100 centimeters (39 in), 125 centimeters (49 in), 150 centimeters (60 in), and 175 centimeters (69 in). Select sites also have thermocouples located at 200 centimeters (79 in) and 225 centimeters (89 in).
Temperature and Relative Humidity Sensor - Vaisala - HMP45C, HMP155A
The probes contain a Vaisala capacitive relative humidity sensor and a platinum resistance temperature detector (PRT) for measuring air temperature. For more details, see the Model HMP45C Temperature and Relative Humidity Probe Instruction Manual printed by Campbell Scientific, Inc. and Model HMP155A Temperature and Relative Humidity Probe Instruction Manual printed by Campbell Scientific, Inc.
Tower - Campbell Scientific, Inc. - Model UT30
Select sites have equipment mounted on a 10-meter (33 ft) aluminum tower which is cemented into the ground. For more details, see UT20 and UT30 Instruction Manual printed by Campbell Scientific, Inc.
Tripod - Campbell Scientific, Inc. - CM106B, CM110
Instrumentation at the majority of sites are mounted on to a 3-meter (10 ft) aluminum tripod. For more details, see CM106B Instruction Manual and CM110, CM115, and CM120 Instruction Manual printed by Campbell Scientific, Inc.
Soil Moisture - Campbell Scientific, Inc. - CS655 Soil Moisture Reflectometer
Volumetric water content and corresponding soil temperatures are measured at 10 centimeters (4 in), 20 centimeters (8 in), 50 centimeters (20 in), and 100 centimeters (40 in). In collaboration with the USGS, the Red River Valley sites also include measurements at 30 centimeters (12 in) and 75 centimeters (30 in).
Wind Speed and Direction - R.M. Young Company - Heavy Duty Wind Monitor HD Model 05108
NDAWN measures wind direction and speed 3 meters (10 ft) above the soil surface and also at 10 meters (30 ft) on select tower sites. The wind direction is the average hourly direction from which wind is blowing. Therefore, starting with degrees clockwise from true north, North = 0; NE = 45; E = 90; S = 180; SW = 225; W = 270; etc. through 360. For more details, see Heavy Duty Wind Monitor HD Model 05108 Instruction Manual printed by R.M. Young Company.