Historically, the primary national resource for high-quality, ground-based solar data has been the solar monitoring network maintained by the National Oceanic and Atmospheric Administration’s (NOAA’s) National Weather Service (NWS). Over the years, this network suffered periodic funding reductions. In the late 1970s it would have disappeared altogether if not for support by the U.S. Department of Energy because of the increased interest in renewable energy technologies. However, in the early 1990s the NWS decided to terminate its solar measurement activities altogether, as part of a modernization and streamlining program. Since that time there have been several efforts, including interagency efforts, to resurrect a national network. A review is provided here of some of the current major regional and national solar monitoring activities underway in the U.S. This review identified over three-dozen stations operated by regional and national organizations throughout the U.S. National networks include the NOAA/ATDL (Atmospheric Transport and Diffusion Laboratory) ISIS/SURFRAD (Integrated Surface Insolation System/SURFace RADiation) network, the NOAA/CMDL (Climate Modeling and Diagnostic Laboratory) Baseline Solar Radiation Network and other research stations, and the NREL CONFRRM/ HBCU (Cooperative Network for Renewable Resource Measurements/Historically Black Colleges and Universities) network. This national-scale network is supplemented by regional stations such as the Atmospheric Radiation Measurement Program’s (ARM’s) Central Facility in Lamont, OK, and university-supported stations such as those operated by the University of Texas Solar Laboratory, the University of Michigan, the University of Oregon Solar Energy Laboratory, and the State University of New York/Albany. When additional regional stations are added to the central station operated by some of these organizations (such as the 21-station ARM network and the Pacific Northwest Solar Monitoring Network operated by the University of Oregon), the total number of stations that could be viewed as part of a national network can increase substantially. The common thread here is that each network or station supports multi-component measurements, common calibration practices traceable to world standards, common sampling and data quality assessment procedures, and web-based data dissemination. Thus, although solar monitoring programs throughout the U.S. are maintained by several agencies or organizations for somewhat independent purposes, there are informal agreements in place to cost share resources and collaborate on data quality assessment, calibration, and data dissemination procedures in a way that provides some commonality and uniformity across all stations.

The spatial coverage offered by this national monitoring program is still inadequate for the solar energy industry. Thus, over the years a number of steps have been taken to supplement measured data with modeled estimates derived from independent measurements. For example, NREL developed a National Solar Radiation Data Base, which provides modeled estimates of solar insolation for 239 National Weather Service stations, making use of the extensive cloud cover reports available from these stations. More recently, several activities to provide high spatial resolution satellite-derived estimates of insolation, using models that use imagery from Geostationary Operational Environmental Satellites (GOES) and Polar Orbiting Environmental Satellites (POES), as well as ground-based observations, have also been undertaken. These supplemental activities are also summarized in this paper.