ARM/GCIP NESOB-96 5 Minute Surface Composite 1.0 General Description The GEWEX Continental-Scale International Project (GCIP) Near- Surface Observation Data Set (NESOB) 1996 ARM 5 Minute Surface Composite is composed of data from the Department Of Energy (DOE) Atmospheric Radiation Measurement Surface (ARMSFC) Network within the NESOB 1996 domain. This Surface Composite contains data for the NESOB 1996 time period (01 April 1996 through 30 September 1996) and for the NESOB 1996 which is approximately 34N to 39N latitude and 94.5W to 100.5W longitude. This dataset was not quality controlled by UCAR/JOSS. 2.0 Detailed Data Description 2.0.1 DOE ARM Surface Algorithms The DOE ARM Surface (ARMSFC) 5-minute values were derived from ARMSFC 1-minute data. The ARMSFC instrument readouts were every second for all variables except 1 minute for barometric pressure. The detailed descriptions of the algorithms used to produce ARMSFC one minute data are not currently available. A description of the uncertainties for each recorded parameter is given below. Temperature/Relative Humidity The ARMSFC 1-minute surface air temperatures were measured at two meters above the ground with a resolution of 0.01 degrees C. The measurement of the air temperature has an uncertainty of +/- 0.45 C for wind speeds >/= 6.00 m/s, +/- 0.89 C for wind speeds >/= 3.00 m/s, +/- 1.46 C for wind speeds >/= 2.00 m/s, and +/- 3.07 C for wind speeds >/= 1.00 m/s. Errors included in the uncertainty for temperature are radiation error, sensor interchangeability, bridge resistor precision, and polynomial curve fitting. Relative humidity (RH) was measured at two meters above the ground. The uncertainty in the recorded relative humidity values is +/- 2.06% RH for RH values from 0 to 90% and +/- 3.04% RH for RH values from 90 to 100%. Errors included in the uncertainty for relative humidity are calibration uncertainty, repeatability, temperature dependence, long term (1 yr) stability, and A/D conversion accuracy. Wind speed dependence and radiation dependence have not been considered. Dewpoint temperature was computed by JOSS using station pressure, temperature, and relative humidity (Bolton, 1980). Station Pressure and Derived Pressure Elements The barometric station pressures were measured at 1 meter above the ground. The uncertainty in the recorded station pressure values is +/-0.035 kPa. Errors included in the uncertainty are linearity, hysteresis, repeatability, calibration uncertainty, temperature dependence, and long-term (1 year) stability. Wind speed dependence was not considered. Wind Speed and Direction The ARMSFC 1-minute wind observations were taken at 10 meters above the ground. The uncertainty in the recorded wind speed values is +/- 1% from 2.5 to 30 m/s, -0.12 to +0.02 m/s at 2.0 m/s, -0.22 to +0.00m/s at 1.5 m/s, -0.31 to -0.20 m/s at 1.0 m/s, -0.51 to -0.49 m/s at 0.5 m/s. Errors included in the uncertainty are calibration accuracy, data logger timebase accuracy, and bias by underestimation due to threshold. The latter assumes a normal distribution of winds about the mean with standard deviations ranging between 0.25 and 1.00 m/s. The uncertainty in the recorded wind direction values is +/- 5.0 deg for wind speeds >1.0 m/s and +/- 180.0 deg for wind speeds