Cloud cover is an important ingredient to compute incoming longwave radiation into lakes. Until a few years ago, the cloud cover algrithm (Unsworth & Monteith, 1975) was used, but recently replaced by the one of Crawford & Duchon (1999). The former directly uses fractional cloud cover as input, while the latter uses the solar index (i.e. the ratio between actual and theoretical incoming solar radiation). Currently, we recommend using cloud cover as input (not solar index) in the manual, but in "operational simstrat" solar index is used and not cloud cover.
Although the resulting differences are probably minor in practice, we should define a clear way of dealing with cloud cover and solar index and check the forcing methods for consistency.
Cloud cover is an important ingredient to compute incoming longwave radiation into lakes. Until a few years ago, the cloud cover algrithm (Unsworth & Monteith, 1975) was used, but recently replaced by the one of Crawford & Duchon (1999). The former directly uses fractional cloud cover as input, while the latter uses the solar index (i.e. the ratio between actual and theoretical incoming solar radiation). Currently, we recommend using cloud cover as input (not solar index) in the manual, but in "operational simstrat" solar index is used and not cloud cover.
Although the resulting differences are probably minor in practice, we should define a clear way of dealing with cloud cover and solar index and check the forcing methods for consistency.