Uncertainty of the Ice Particles Median Mass Diameters Retrieved from the HAIC-HIWC Dataset: a Study of the Influence of the Mass Retrieval Method 2019-01-1983
In response to the ice crystal icing hazard identified twenty years ago, aviation industry, regulation authorities, and research centers joined forces into the HAIC-HIWC international collaboration launched in 2012. Two flight campaigns were conducted in the high ice water content areas of tropical mesoscale convective systems in order to characterize this environment conducive to ice crystal icing. Statistics on cloud microphysical properties, such as Ice Water Content (IWC) or Mass Median Diameter (MMD), derived from the dataset of in situ measurements are now being used to support icing certification rulemaking and anti-icing systems design (engine and air data probe) activities. This technical paper focuses on methodological aspects of the derivation of MMD. There is currently no direct method to measure the MMD of an ice particle size distribution (PSD). Instead, MMD were estimated from PSD and IWC using a multistep process. Critical in this process is the mass retrieval method necessary to estimate mass distributions, from which MMDs are calculated. This step implies assumptions that make the MMD values prone to uncertainty due to methodological choices. In complement to other studies presenting reference MMD values retrieved in the high IWC environment of the HAIC-HIWC field campaigns, this paper deals with the uncertainty that still needs to be quantified. Indeed, a state-of-the-art mass retrieval technique was used to compute reference MMD values. Recently, progress has been achieved in the retrieval of atmospheric ice crystal mass distributions from in situ measurements. A new method, based on strictly different assumptions, is now available and the HAIC-HIWC dataset has been processed using this alternate mass retrieval method. In this study, a comparison is made between independently retrieved sets of MMD values in order to estimate uncertainty associated with MMD statistics. The comparison supporting the uncertainty estimation may also include other technical aspects such as the influence of the definitions of the size parameter commonly used to describe the size of ice particles.
Pierre Coutris, Alfons Schwarzenboeck, Delphine Leroy, Alice Grandin, Fabien Dezitter, J. Walter Strapp
CNRS, Airbus France, Airbus Helicopters
International Conference on Icing of Aircraft, Engines, and Structures