Degradation of In-Cloud Forward Scattering Spectrometer Probe Measurements in the Presence of Ice Particles

Abstract

Airborne measurements of cloud liquid water content derived from a formvar replicator, a Johnson-Williams probe and a forward scattering spectrometer probe (FSSP) are compared. These show that in the presence of ice crystals the FSSP droplet spectra may be artificially enhanced. Typically the ice produces a flat distribution superimposed on the actual droplet distribution. The concentrations measured by the FSSP in the presence of ice are found to be 2–3 orders of magnitude greater than the actual ice concentrations as measured by the formvar replicator and a 2D-C probe. Possible explanations for the abnormal behavior of the FSSP in the presence of ice particles are discussed.