Evaluation of the Forward Scattering Spectrometer Probe. Part II: Corrections for Coincidence and Dead-Time Losses

Abstract

Cloud particle concentrations measured by the Forward Scattering Spectrometer Probe (FSSP) can be underestimated when particles are either coincident or pass through the sensing area of the probe during the electronic dead-time. In the absence of any corrections, the differences between actual and measured concentrations can typically exceed 15% when aircraft mounted probes measure droplet concentrations > 500 cm−3. The sources of counting losses are described and correctional procedures derived and demonstrated.