This white paper is an update from the Vaisala 2019 “Professional Grade Validation Study” (Vaisala, Oct 2019) and is a companion document to our most recent Global Validation Study (Vaisala, May 2020). The “Professional Grade” study from 2019 looked at the bias of the Vaisala satellite estimate versus high quality observations in the U.S.A. (12 locations for GHI and DNI). The global validation study from 2020 looked at ~200 stations of various quality around the world. This updated “Professional Grade” study increases the sample size of locations in the U.S.A. from 12 to 38. Results show that both “Professional Grade” studies utilizing high quality observations have considerably lower uncertainty than that obtained from the Vaisala global validation, even when just considering those stations in the U.S.A. Furthermore the uncertainty of the previous “Professional Grade” study of approximately 2.2% (at one standard deviation) is essentially unchanged as the sample size of stations in the U.S.A. increases from 12 to 38.
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