Abstract :
REST2, a high-performance model to predict cloudless-sky broadband irradiance, illuminance and photosynthetically active radiation
(PAR) from atmospheric data, is presented. Its derivation uses the same two-band scheme as in the previous CPCR2 model, but
with numerous improvements. Great attention is devoted to precisely account for the effect of aerosols, in particular.
Detailed research-class measurements from Billings, OK are used to assess the performance of the model for the prediction of direct,
diffuse and global broadband irradiance. These measurements were made in May 2003 during a sophisticated radiative closure experiment,
which involved the best radiometric instrumentation currently available and many ancillary instruments. As a whole, these exceptional
measurements constitute the only known modern benchmark dataset made specifically to test the intrinsic performance of
radiation models. Using this dataset as reference, it is shown that REST2 performs better than CPCR2 for irradiance, illuminance or
PAR predictions. The availability of the turbidity data required by REST2 or other similar models is also discussed, as well as the effect
that turbidity has on each component of broadband irradiance, PAR irradiance and illuminance, and on the diffuse/global PAR ratio.
2007 Elsevier Ltd. All rights reserved.
