Synergistic radar and sub-millimeter radiometer retrievals of ice hydrometeors in mid-latitude frontal cloud systems

• Published in: Atmospheric measurement techniques 2022-02, Vol.15 (3), p.677-699
• Main Authors: Pfreundschuh, Simon, Fox, Stuart, Eriksson, Patrick, Duncan, David, Buehler, Stefan A, Brath, Manfred, Cotton, Richard, Ewald, Florian
• Format: Article
• Language: English
• Subjects: Aircraft; algorithm; Algorithms; Altitude; Analysis; Arctic clouds; Arctic weather; Atmospheric models; Calibration; climate modeling; Climate models; cloud; Cloud systems; Clouds; Datasets; Diameters; Frontal clouds; Gas absorption; hydrometeorology; Hydrometeors; Ice; Ice clouds; Ice particles; In situ measurement; Latitude; Meteorological satellites; midlatitude environment; Modelling; Moisture content; Particle shape; Particle size; Polar environments; Precipitation (Meteorology); Properties; Radar; Radiative transfer; radiometer; Radiometers; Remote sensing; Retrieval; Rosette shapes; Satellite imagery; Satellites; Sensitivity; Sensors; Shape; Simulation; Simulators; Uncertainty; Water content; Weather
• ISSN: 1867-8548; 1867-1381; 1867-8548
• DOI: 10.5194/amt-15-677-2022

Accurate measurements of ice hydrometeors are required to improve the representation of clouds and precipitation in weather and climate models. In this study, a newly developed, synergistic retrieval algorithm that combines radar with passive millimeter and sub-millimeter observations is applied to observations of three frontally generated, mid-latitude cloud systems in order to validate the retrieval and assess its capabilities to constrain the properties of ice hydrometeors. To account for uncertainty in the assumed shapes of ice particles, the retrieval is run multiple times while the shape is varied. Good agreement with in situ measurements of ice water content and particle concentrations for particle maximum diameters larger than 200 µm is found for one of the flights for the large plate aggregate and the six-bullet rosette shapes. The variational retrieval fits the observations well, although small systematic deviations are observed for some of the sub-millimeter channels pointing towards issues with the sensor calibration or the modeling of gas absorption. For one of the flights the quality of the fit to the observations exhibits a weak dependency on the assumed ice particle shape, indicating that the employed combination of observations may provide limited information on the shape of ice particles in the observed clouds. Compared to a radar-only retrieval, the results show an improved sensitivity of the synergistic retrieval to the microphysical properties of ice hydrometeors at the base of the cloud.