Investigation of Microphysical Properties of DCS using Aircraft in-Situ Measurements. Part I: the Ice-Phase Layer of DCS

The 2011 Midlatitude Continental Convective Clouds Experiment (MC3E) was a highly successful field campaign with 15 convective cases sampled by the University of North Dakota (UND) Citation II aircraft in addition to multiple ground-based sensors. There were at least six deep convective systems (DCS) (25 April, 27 April, 11 May, 20 May, and 23–24 May 2011), including the classic DCS case on 20 May 2011, which has drawn much attention from observational and modeling communities. During the experiment, microphysical properties of DCS were studied, including ice water content (IWC) at the upper layer of DCSs. Due to instrumentation limits, it was believed that the total water content (TWC) measured by Nevzorov hot-wire sensor could not capture all the ice crystals especially those with sizes greater than 900 µm. This study first eliminated the contamination of super-cooled liquid water by determining the accurate temperature threshold of pure ice-phase layer using multi-sensors including icing detector records and 2DC image reading results, then recalibrated and developed a series of new mass-dimensional relationships to generate the best-estimate IWC for each case. Comparisons of IWCs calculated from particle size distribution (PSD ≤ 900 µm) and entire spectrum (best-estimate) with Nevzorov measurements have shown that there are very good agreement in IWCs between calculation from PSD (≤ 900 µm) and Nevzorov measurements, while best-estimate IWCs are larger than Nevzorov measurements by a factor of 1-1.78, depending on depending on the proportion of ice crystals greater than 900 µm exist in the clouds. Comparing the properties of the ice-phase layer of DCS with convectively generated cirrus clouds during the CRYSATLL-FACE, the average temperature and height from the MC3E cases are -27.6 ^oC and 7.6 km, about 10 ^oC higher and 3 km lower than those from the CRYSATLL-FACE cases. The averaged IWC from the MC3E (0.59 g m^-3) is greater than the CRYSATLL-FACE by a factor of three, representing the different characteristics of microphysical properties between these two types of clouds. The good agreement in IWC between the anvil region of 20 May (0.22 g m^-3) and the CRYSATLL-FACE cirrus clouds (0.184 g m^-3) reveals the inherent similarity between anvil region of DCS and cirrus clouds. This method can be used for the correction of past Nevzorov IWC measurement and retrieval of other microphysical properties in the pure ice-phase layer of DCS.