The Microphysics of Stratiform Precipitation During OLYMPEX: Compatibility Between Triple-Frequency Radar and Airborne In Situ Observations

• Published in: Journal of Geophysical Research: Atmospheres
• Main Authors: Tridon, F, Battaglia, A, Chase, RJ, Turk, FJ, Leinonen, J, Kneifel, S, Mroz, K, Finlon, J, Bansemer, A, Tanelli, S, Heymsfield, AJ, Nesbitt, SW
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union (AGU), Wiley 2019
• Subjects: solid and liquid precipitation; multifrequency radar; riming versus aggregation; snowfall and rainfall; scattering models; optimal estimation; Leicester; The Spectre; Leinonen; Antarc*; Antarctica
• Online Access: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JD029858; http://hdl.handle.net/2381/45475; https://doi.org/10.1029/2018JD029858

The link between stratiform precipitation microphysics and multifrequency radar observables is thoroughly investigated by exploiting simultaneous airborne radar and in situ observations collected from two aircraft during the OLYMPEX/RADEX (Olympic Mountain Experiment/Radar Definition Experiment 2015) field campaign. Above the melting level, in situ images and triple-frequency radar signatures both indicate the presence of moderately rimed aggregates. Various mass-size relationships of ice particles and snow scattering databases are used to compute the radar reflectivity from the in situ particle size distribution. At Ku and Ka band, the best agreement with radar observations is found when using the self-similar Rayleigh-Gans approximation for moderately rimed aggregates. At W band, a direct comparison is challenging because of the non-Rayleigh effects and of the probable attenuation due to ice aggregates and supercooled liquid water between the two aircraft. A variational method enables the retrieval of the full precipitation profile above and below the melting layer, by combining the observations from the three radars. Even with three radar frequencies, the retrieval of rain properties is challenging over land, where the integrated attenuation is not available. Otherwise, retrieved mean volume diameters and water contents of both solid and liquid precipitation are in agreement with in situ observations and indicate local changes of the degree of riming of ice aggregates, on the scale of 5 km. Finally, retrieval results are analyzed to explore the validity of using continuity constraints on the water mass flux and diameter within the melting layer in order to improve retrievals of ice properties. The work done by F. Tridon was supported in part by the European Space Agency under the activity Multifrequency Instruments study (ESA‐ESTEC) under Contract 4000120689/17/NL/IA and by the Atmospheric System Research project “Ice processes in Antarctica: Identification via multiwavelength active and passive measurements and model evaluation” (DE‐SC0017967). The work by A. Battaglia was supported by the project “Radiation and Rainfall” (RP18G0005) funded by the UK National Center for Earth Observation. The work by K. Mroz was performed at the University of Leicester, under contract with the National Centre for Earth Observation. The research of F. J. Turk, S. Tanelli, and J. Leinonen was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract from NASA. This research used the SPECTRE and ALICE High‐Performance Computing Facilities at the University of Leicester. We thank all the participants of OLYMPEX and RADEX'15 for collecting the data used in this study, which were obtained from the NASA GHRC OLYMPEX data archive (doi: https://doi.org/10.5067/GPMGV/OLYMPEX/DATA101). Peer-reviewed Publisher Version