Bonanza Creek Experimental Forest: UV measurements: hourly (1988 - Present)

In 1993, Eppley total UV radiometers (TUVR) were installed at each climate station on 21 April at LTER1 and 5 May at LTER2. These radiometers consist of a Weston selenium barrier-layer photoelectric cell with a sealed-in quartz window, a bandpass filter to restrict the wavelength response of the photcell to the designed range (295-385 nm), and a diffusing disc of Virgin Teflon to reduce the light intensity at the filtered photocell and also to improve the adherence of the instrument to the Lambert cosine law. The disc is nearly uniform diffusing over the wavelength range of interest, as well as geometrically within the system. The terminals of the photocell are connected through a precision resistor and the signal measured as a voltage drop across the resistor. Winter measurements may be inaccurate due to snow cover.