Droplet Spectra Measurements with the FSSP-100. Part I: Low Droplet Concentration Measurements

Abstract

Entrainment-mixing processes such as droplet spectrum broadening and its impact on the onset of precipitation are, among many others, physical phenomena whose experimental study relies on in-cloud airborne measurements. For more than 30 yr, droplet sizing has been performed mostly with the Forward Scattering Spectrometer Probe (FSSP-100). The probe performance was extensively studied and probabilistic procedures were developed for characterizing the transfer function of the probe and correcting instrumental artifacts in the measurement of both the total droplet concentration and the droplet spectral shape. These procedures are revised here with a focus on low concentration measurements and the spectral distortion that may be generated by the real-time pulse processing, when the actual droplet spectrum is broad. The transfer matrix method is extended to account for this instrumental artifact.