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At NEAR, select data with sun elevation greater than 15 degrees (this limit is not critical). The median ratio of Rsw.global/Rsw.in = 0.9938. I note, however that there is hysteresis in the plot of Rsw.in.global versus Rsw.in. This is consistent with the observation that the up-facing radiometers at NEAR were not perfectly leveled because of problems with the radiometer mounting device.
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At FLR we select data with sun elevation greater than 20 degrees (to clear the sidewalls). The median ratio of Rsw.global/Rsw.in = 1.0358, which is
presumably perhaps higher because the bird droppings obscured Rsw.in at times. I conclude that Rsw.global could be used as a
reasonable surrogate for Rsw.in during those times
. Rsw.
in.flr data were deleted from Oct 14-20 when the residuals from a linear fit of Rsw.global.flr vs Rsw.in.flr exceeded 20 W/m^2, as indicated by the highlighted data in the right-hand plot below. After deleting that Rsw.in.flr data, the linear fit changed slightly to Rsw.global.flr = 1.029*Rsw.in.flr + 1.07 W/m^2.
