Evolution of DARDAR-CLOUD ice cloud retrievals: new parameters and impacts on the retrieved microphysical properties

Quitterie Cazenave (1) , Marie Ceccaldi (1) , Julien Delanoë (1) , Jacques Pelon (2) , Silke Gross (3) , Andrew J Heymsfield (4)

1 SPACE - LATMOS
2 TROPO - LATMOS
3 IPA - DLR Institut für Physik der Atmosphäre = DLR Institute of Atmospheric Physics
4 NCAR - National Center for Atmospheric Research [Boulder]

In this paper we present the latest refinements brought to the DARDAR-CLOUD product, which contains ice cloud microphysical properties retrieved from the cloud radar and lidar measurements from the A-Train mission. Based on a large dataset of in situ ice cloud measurements, the parameterizations used in the microphysical model of the algorithm-i.e. the normalized particle size distribution, the mass-size relationship, and the parameterization of the a pri-ori value of the normalized number concentration as a function of temperature-were assessed and refined to better fit the measurements, keeping the same formalism as proposed in DARDAR basis papers. Additionally, in regions where li-dar measurements are available, the lidar ratio retrieved for ice clouds is shown to be well constrained by the lidar-radar synergy. Using this information, the parameterization of the lidar ratio was also refined, and the new retrieval equals on average 35 ± 10 sr in the temperature range between −60 and −20 • C. The impact of those changes on the retrieved ice cloud properties is presented in terms of ice water content (IWC) and effective radius. Overall, IWC values from the new DARDAR-CLOUD product are on average 16 % smaller than the previous version, leading to a 24 % reduction in the ice water path. In parallel, the retrieved effective radii increase by 5 % to 40 %, depending on temperature and the availability of the instruments, with an average difference of +15 %. Modifications of the microphysical model strongly affect the ice water content retrievals with differences that were found to range from −50 % to +40 %, depending on temperature and the availability of the instruments. The largest differences are found for the warmest temperatures (between −20 and 0 • C) in regions where the cloud microphysical processes are more complex and where the retrieval is almost exclusively based on radar-only measurements. The new lidar ratio values lead to a reduction of IWC at cold temperatures, the difference between the two versions increasing from around 0 % at −30 • C to 70 % below −80 • C, whereas effective radii are not impacted.

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]; Météorologie

Quitterie Cazenave, Marie Ceccaldi, Julien Delanoë, Jacques Pelon, Silke Gross, et al.. Evolution of DARDAR-CLOUD ice cloud retrievals: new parameters and impacts on the retrieved microphysical properties. Atmospheric Measurement Techniques, 2019, 12 (5), pp.2819-2835. ⟨10.5194/amt-12-2819-2019⟩. ⟨insu-02131501⟩