Surface Solar Radiation in North America: Observations, Reanalyses, Satellite and Derived Products

Abstract:

Observations of daily surface solar/shortwave radiation data from over 4000 stations have been gathered, covering much of the lower 48 continental states of the US as well as portions of Alberta and British Columbia, Canada. The quantity of data increases almost linearly from 1998 when only several hundred stations had data. A quality control procedure utilizing threshold values along with computing the clear sky radiation envelope for individual stations was implemented to both screen bad data and rescue informative data. Over two thirds of the observations are seen as acceptable. Fifteen different surface solar radiation products are assessed relative to observations, including reanalyses (20thC, CFSRR, ERAI, JRA-55, MERRA, NARR, NCEP), derived products (CRU_NCEP, DAYMET, GLDAS, GSWP3, MsTMIP, NLDAS) and two satellite products (CERES and GOES). All except the CERES product are daily or finer in temporal resolution. The root mean square error of spatial biases is greater than 18Wm^-2 for 13 of the 15 products over the summer season (June, July, August). None of the daily resolution products fulfill all three desirable criteria of low (<5%) annual or seasonal bias, high correlation with observed cloudiness and correct distribution of clear sky radiation. Some products display vestiges of underlying algorithm issues (e.g. from MTCLIM ver4.3) or bias correction methods. A new bias correction method is introduced that preserves clear sky radiation values and better replicates cloudiness statistics. The current quantity of data over the continental US suggests a solar radiation product based on, or enhanced with, observations is feasible.