ARM/GCIP NESOB-96 NOAA/ATDD Little Washita Watershed Soil Temperature Dataset 1.0 General Description The National Oceanic and Atmospheric Administration (NOAA)/ Atmospheric Turbulence and Diffusion Division (ATDD) Soil Temperature Dataset is one of several sub-surface datasets provided for the GEWEX Continental-Scale International Project (GCIP) Near Surface Observation Data Set (NESOB) 1996 project. This dataset contains data from one station, the Little Washita Watershed Long Term Flux Site, within the NESOB 1996 domain (100.5W to 94.5W longitude and 34N to 39N latitude) and time period (01 April 1996 through 30 September 1996). 2.0 Detailed Data Description The first long-term flux monitoring site was established within the Little Washita Watershed, near Chickasha, Oklahoma, which is within the LSA-SW region. Soil temperature is measured at the base of the tower (34 58' N, 97 77' W) which is located about one quarter mile north of State Road 19 within a grazed pasture owned by Earl Morris. Pasture surrounds the 3 meter tower in all sectors providing a minimum fetch of 200 meters over gently rolling terrain. The soil at this site (upper 60 cm) is classified as clay loam with sand, silt, and clay fractions of 25%, 45%, and 30%, respectively. The bulk density at this site is 1.6 g/cm3 +/- 0.1. The grasses and vegetation surrounding the tower are occasionally grazed by the farmers cattle. Data Acquisition Soil Temperature is sampled every 2 s with a datalogger and multiplexor (CR21x, Campbell Scientific, Inc.) and averages are computed every 30 minutes. A laptop computer retrieves the soil temperature data from the CR21X datalogger every 30 minutes and appends the data to an existing file. After midnight, the data are copied to separate files with a name, year and calendar day header. The computer is equipped with a modem and cellular phone in order to retrieve the data and conduct occasional system checks. On average, data are retrieved from the laptop computers about once every two days. Power Operation and Management To avoid the constraints of using standard line power, the entire flux/meteorological system is designed to operate on 12 volts DC making it truly remote and portable. The entire flux system, including all the instruments and data logging devices are powered by nine deep-cycle 12 volts DC batteries that are charged daily with solar panels ( M75, Siemans, Inc.). Each solar panel is capable of producing 3 amperes at 12 volts in full sunlight. The batteries are enclosed in an insulated container that is 2/3 submerged into the ground near the base of the tower. Eight solar panels are required at the Little Washita location. Each charging system is controlled with a 30 ampere regulator. The regulator is equipped with a low voltage disconnect option that disconnects electronic devices with the largest power consumption when the battery voltage falls below 11.5 VDC. The entire system continuously draws about 3 amperes at 12 VDC. The 21X datalogger and cellular phone are connected directly to the batteries and operate continuously since they have low power demands. When the regulator disconnects the computer because of low voltage (i.e. long periods of cloudy weather), only standard meteorological data are logged. After the batteries are charged to 12.5 VDC, the computer, IRGA and sonic are reconnected and logging of the flux data resumes. This happens infrequently and only during the winter months when cloudy conditions persist during the relatively short daylight hours. 2.1 Detailed Format Description The NOAA/ATDD Soil Temperature Dataset contains eight metadata parameters and eighteen data parameters and flags. The metadata parameters describe the date, time, network, station and location at which the data were collected. Data values are valid for the 30 minutes preceeding the time of observation. All times are UTC. The data parameters consist of triplets for each depth. Soil temperature is measured at 2 cm, 4 cm, 8 cm, 16 cm, 32 cm, and 64 cm. Table 1 below details the data parameters. The data parameters have an associated Quality Control (QC) flag. A description of the possible QC flag values is listed in Table 2. ------- Parameters Units ---------- ----- Date of Observation UTC Time of Observation UTC Network Identifier Abbreviation of platform name Station Identifier Network Dependent Latitude Decimal degrees, South is negative Longitude Decimal degrees, West is negative Station Occurrence Unitless Station Elevation Meters Soil Temperature Celsius Soil Depth centimeters (2,4,8,16,32,& 64cm) QC flag (See Table 2) Table 2 ------- QC Code Description ------- ----------- U Unchecked G Good M Normally recorded but missing D Questionable B Unlikely N Not available or Not observed. X Glitch E Estimated C Reported precipitation value exceeds 9999.99 millimeters or was negative. T Trace precipitation amount recorded. 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