Surface Radiation Budget (SURFRAD) Network 1-Hour Observations

Radiation measurements at SURFRAD stations cover the range of the electromagnetic spectrum that affects the earth/atmosphere system. Direct solar radiation is monitored with a Normal Incidence Pyrheliometer (or NIP) mounted on the solar tracker. Downwelling global solar radiation is measured by an upward-viewing broadband pyranometer. The diffuse, or sky component, of solar radiation is measured by a shaded Eppley 8-48 pyranometer mounted on a platform that is attached to the solar tracker. A ball shades the sensor of the diffuse pyranometer, thus allowing only the radiation scattered by the atmosphere to be measured. A Precision Infrared Radiometer (PIR), or pyrgeometer, is also mounted on the solar tracker shade platform to measure downwelling thermal infrared radiation. 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