A Method for Validating FSSP Measurements Using Observational Data

Abstract A validation method of measurements from the forward-scattering spectrometer probe (FSSP) allowing preliminary analysis and verification of rough data is presented. It is based on the comparison of observed spectral distributions from undiluted cloudy air with theoretical adiabatic ones. The latter are obtained using an ascending adiabatic cloud-parcel model and the corresponding cloud-base conditions. A two-step approach is used to correct observed spectral distributions and is illustrated with data collected during the 1985 Joint Hawaii Warm Rain Project (JHWRP). The procedure provides an alternate way of obtaining the response matrix for an FSSP and can be used to validate the laboratory-derived response matrix. The results obtained (spectral characteristics and liquid water contents) agree well with the ones calculated from the laboratory characterization, which was made after the experiment, taking into account the laser beam nonuniformities.