COLOR FIGURE 3.23 The WRR is determined by a group of absolute cavity radiometers named the World Standard Group. At the moment, the WSG is composed of six instruments: PMO-2, PMO-5, CROM-2L, PACRAD-III, TMI-67814, and HF-18748.
COLOR FIGURE 5.3 Picture of a copper-constantan thermopile manufactured by Eppley Laboratory, Inc. Constantan wire is wrapped around a solid core and then dipped into a cop¬per bath. (Photograph by Warren Gretz, NREL staff photographer.)
COLOR FIGURE 5.4 Picture of Kipp & Zonen CM 22 pyranometers in ventilators at SRRL in Colorado.
COLOR FIGURE 5.12 Three ventilators mounted on a Sci-Tech tracker. Going from right to left, the ventilator on the left is a Swiss PMOD ventilator holding a Kipp & Zonen CM 22 pyranometer. The ventilator is mounted on an Eppley ventilator base so the height of the dome matches the height of the domes of the other instruments. PMOD also makes a base for leveling. The middle ventilator is a Schenk ventilator for Schenk Star pyranometers. The ventilator on the left is an Eppley ventilator holding an Eppley precision infrared radiometer or pyrgeometer.
COLOR FIGURE 6.3 The Eppley model SBS shadowband blocks direct sunlight on a clear summer day in Eugene, Oregon. Note that the detector surface is well centered beneath the shadowband. The shadowband blocks a significant part of the brightest region of the clear- day skylight.
COLOR FIGURE 6.4 An example of a shaded-disk measurement of DHI. The arm holds disks that shade each of three black-and-white pyranometers.
COLOR FIGURE 7.2 The Yankee Environmental Systems, Inc. seven-channel multifilter rotating shadowband radiometer model MFR-7.
COLOR FIGURE 9.8 Photograph of the SURFRAD albedo tower near Sioux City, South Dakota. Note the shields that ensure the direct sunlight will not reach the upwelling detector even for minor horizontal leveling errors.
COLOR FIGURE 10.5 Three Eppley PIR pyrgeometers operated in the optimum manner; the instruments are continuously shaded from direct sunlight using an automatic tracker and are placed in heated ventilators to minimize dew formation and dust deposition on the instru¬ment domes.
COLOR FIGURE 12.3 Direct solar transmission of major components of the clear-sky atmosphere (left axis); superimposed on the transmission spectra is the spectral irradiance calculated for these conditions (right axis).
COLOR FIGURE 12.4 The typical human eye’s response for sunlit conditions as specified by the Commission International l’Eclairage (CIE); en.wikipedia.org/wiki/File:Srgbspectrum. png is the source for the color diagram beneath the photopic response plot.
COLOR FIGURE 13.5 Wind anemometers—sonic and vane. Pacific Northwest National Laboratory has developed a special filtering technique to enhance data gathered by an inex-pensive cup anemometer. With the technique, cup anemometer measurements are surpris¬ingly close to those made with a costly and sophisticated sonic anemometer (center of photo). (Courtesy of Warren Gretz, NREL staff photographer.)
COLOR FIGURE 14.10 Photograph of the SURFRAD station near Sioux Falls, South Dakota.
COLOR FIGURE 14.11 Photograph of the SRRL station in Golden, Colorado, looking north. Sample of instruments in continuous use (foreground) and under test at SRRL. Note platform on which the instruments are mounted is a grate that helps to prevent snow from building up around instruments.
COLOR FIGURE 14.13 Photograph of the University of Oregon Solar Radiation Moni¬toring Laboratory monitoring station in Eugene, Oregon. Note that most tilted measure¬ments use a shield to block some of the ground-reflected irradiance.
COLOR FIGURE H.1 Northern hemisphere summertime Campbell–Stokes measurement of sunshine duration. Fractional hours with bright sunshine are estimated by an analyst and hand recorded.