Inferring cloud deposition to a forest canopy using a passive cloudwater collector

Abstract

A widely used passive cloudwater collector was operated continuously along with an automated canopy water throughfall measurement system at a high elevation spruce forest site. Cloudwater collection rate (Rc) and throughfall (TF) rate were examined to determine their interrelationship. In addition, the use of the cloudwater collector for inferring cloud liquid water content was examined. The degree of direct hourly correlation was fairly good between Rc and canopy TF rate for non‐rain periods when the canopy was saturated (the former explained 58% of the variance in the latter). The correlation was even better (R² = 0.84) when TF rate was time‐lagged one hour. Estimated liquid water content, using collector data, was characterized by a large degree of uncertainty. This uncertainty appears to be caused, to a large extent, by the inability of the estimation method to account for the variation in cloudwater collection efficiency as a function of wind speed and droplet size.