Evaluation of airborne radar-lidar retrieval of ice water content using in-situ probes

Cloud water content and how that water is distributed across hydrometeors are fundamental cloud microphysical properties that influence cloud dynamical and radiative properties. This study utilizes in-situ and remote sensing data collected by the University of Wyoming King Air research aircraft during the Colorado Airborne Multi-phase Cloud Study, 2010-2011 (CAMPS) field campaign to study the reliability of different cloud water content measuring instruments. It has been shown in several previous studies and again demonstrated here from the CAMPS dataset that Forward Scattering Spectrometer Probe (FSSP) measurements are subject to contamination by shattering artifacts in ice and mixed phase clouds. Contaminated measurements from CAMPS show a significant overestimation of large (D > 28 microm) particles and derived liquid water content (LWC). A new approach is developed to characterize, quantify and correct the shattering contribution in FSSP measurements using ice particle information measured by an OAP cloud probe (2D-C). Comparisons with cloud droplet probe (CDP) measurements show that this new approach adequately corrects for ice shattering effects. This new approach can also be applied to standard FSSP historical datasets. These studies may have erroneous conclusions that can be re-evaluated based on this new correction. University of Colorado closed-path tunable diode laser hygrometer (CLH) total water measurements are used to develop a mass-length relationship for CAMPS dataset to calculate ice water content (IWC) from 2D-C size distribution. Then, these well characterized in-situ instruments are used to evaluate IWC retrievals from combined radar and lidar measurements. Comparison of near flight level remote sensing IWC retrievals with in-situ measurements indicates statistically reasonable agreements (difference in mean values about 33%) providing confidence on the retrieved vertical IWC profile. The collocated airborne radar-lidar measurements combined with in-situ measurements provide detailed information about cloud microphysical and radiative properties. These properties can be used to develop and improve cloud parameterizations in numerical models.