Surface Radiation Budget (SURFRAD) Network 1-Hour Observations

A third broadband pyranometer is mounted facing downward on a cross arm near the top of the 10-meter tower to monitor solar radiation reflected from the surface. Another pyrgeometer, also mounted facing downward on the cross arm of the tower, senses thermal radiation upwelling from the surface. Two instruments on the main platform monitor wavebands of special interest.

A UVB radiometer measures the degree of harmful ultraviolet radiation (280-320 nm) that evades the ozone layer and reaches the surface. The other monitors the intensity of the waveband active in photosynthesis (400 to 700 nm). The last radiometer in the SURFRAD suite is the Multi-Filter Rotating Shadowband Radiometer (MFRSR) which measures both global and diffuse solar radiation in one broadband channel and six narrow bands of the solar spectrum.

Instruments for measuring wind direction and speed, air temperature, and relative humidity are mounted at the top of the tower. Station pressure is measured at the main platform. Campbell Scientific Inc. data logging equipment samples and records signals from all instruments except the MFRSR.

The sampling rate for the radiometers and the meteorological instruments is one second, and the logger has been programmed to record one-minute averages of the one-second samples beginning in 2009-01-01. Before 2009-01-01 three-minute averages were recorded. Conversion to physical units through calibration factors is done in post processing.

The MFRSR has its own logger that spot samples at 15-second intervals and records one-minute averages of the output voltages. Only one-hour data are archived at NCEI. In 1999 and 2000, total sky imagers (TSI) were installed at all SURFRAD stations.

This device documents sky conditions and cloud fraction every minute. These measurements aid in the interpretation of the radiation measurements during the daytime, and also offer ground truth for satellite estimates of cloud fraction. Three stations now have surface latent, sensible, and soil heat flux systems, promoting them to surface energy budget stations.

These surface energy budget measurements are welcomed by those who develop new atmospheric and hydrologic models that employ explicit surface physics