CStelzerKED

The NSRDB TMY data at 33.26, -95.21 imports with PVsyst warnings that the "clearness index of the best clear days seems high with respect to the clear day model." I've checked another satellite grid nearby, and imported several different TMY, TGY years. They all say the same thing. Shows maybe 1.15 index at the highest day, and not crossing 1.0 until about 90 days. Also checked a flat dry spot in Arizona for comparison and didn't have that warning. For the Arizona data the max index was ~ 1.05, with a long stretch of days very close to 1.0. So something about the NSRDB data in NE Texas seems skewed. It appears to be overpredicting in the winter/spring/autumn, and almost spot on in the summer months. Can anyone explain the story behind the data? Best clear days Ktcs chart from meteo tables and graphs analysis V7.0.7