The Surface Radiation Budget Network (SURFRAD) was established in 1993 by NOAA's Air Resources Laboratory through the support of NOAA's Office of Global Programs. Its primary objective is to support climate, global change, and related research with high quality continuous measurements of the surface radiation budget. The first four stations at Bondville, IL; Fort Peck, MT; Goodwin Creek, MS; and Boulder, CO were installed in 1994 and 1995. In March and June of 1998, two new stations were added at Desert Rock, NV, and near Penn State, respectively. Station locations were chosen to represent diverse climates of the United States. To accommodate satellite validation needs, special consideration was given to places where the landform and vegetation are homogeneous over an extended region. In addition, Fort Peck and Goodwin Creek were located in well monitored drainage basins to support hydrologic research.
Independent measures of upwelling and downwelling, solar and thermal infrared are the primary measurements. Ancillary measurements include direct and diffuse solar, photosynthetically active and UVB radiation, spectral solar, and meteorological parameters. Quality-controlled daily files of three-minute data from each station are distributed in near real time by anonymous FTP, usually within twenty-four hours of receipt of the data.
Good quality assurance and quality control are key to the network's success. Radiometers are calibrated and exchanged annually at each station. Before and after they are deployed, the instruments are compared against standards maintained at our field test facility at Table Mountain. This provides a pseudo overlap of incoming instruments and their replacements. These practices have paid off with high data recovery rates. Over the first three years of the network, well over 90% of the possible data has been successfully recovered, with many parameters having over a 95% recovery rate.
Efforts are underway to make SURFRAD stations even more suitable for climate research. A fundamental problem in climate is the effect of clouds on solar radiation. In response, automated whole-sky imagers will be installed at each SURFRAD station. This information will help in the interpretation of radiation measurements, and also will offer ground truth for estimates of cloud fraction made by numerical models and satellite-based algorithms. Currently, NASA is using SURFRAD data to validate surface radiation budget estimates derived from the new series of EOS satellites. Software to infer cloud effects from the solar radiation measurements themselves has also been developed and applied to SURFRAD data. To achieve full surface energy budget information, plans are ongoing to locate sensible and latent heat flux measurement systems at SURFRAD stations. There is already an energy flux tower near the Bondville station, and there are plans to install them at Goodwin Creek and Fort Peck. The SURFRAD network, its data system, results, and plans will be discussed at the conference.