The impact of deep cumulus reflection on the ground-level global irradiance

The magnitude of solar irradiance reflected from deep cumulus clouds to the ground was evaluated using observations along the Front Range of Colorado. Solar-irradiance reflection around noon was found to cause increases of up to about 250 W/m sq. Enhancements of the global irradiance measured at the surface were observed to persist for 15-30 min. Occasionally, the increased global irradiance prevailed for a period of about 1 h. Model simulations implied similar patterns. It was evaluated that in some locations cloud reflection of solar irradiance may have a seasonal nonrandom pattern, thus increasing its significance. Estimation of the applied impact of cloud-reflected solar irradiance in several relevant situations is provided.