Determination of in-flight icing zones in the southeast of Western Siberia

The paper presents icing parameters based on actual weather conditions taken from pilot reports (PIREPs) in the Tomsk aerodrome and shows the feasibility of using satellite information to identify possible in-flight icing zones (by example). From 2011 to 2018, the icing was regularly observed during the period from October to December, averaging 6-7 days per month with a maximum in December 2015 (14 days). The most frequent icing occurred with moderate (52 %) and light (42 %) intensity. Days with severe accumulation of aircraft ice were observed in all seasons, excluding summer, with a maximum of November (8 cases). In more than half of the cases, icing was observed in layers up to 1,000 m thick, just 25 % exceeded 1,500 m and in some cases reached more than 3,500 m. In 75 % of cases, the lower boundary of the icing layer was reported directly from the underlying surface up to 1,500 m, and in some cases, icing was observed from 3 km and above. An analysis of synoptic processes on icing days revealed that approximately 65 % of cases of icing of different intensities were recorded in frontal cloud systems, of which 24 % were on occluded fronts, 35 % on cold fronts, and 41 % on warm fronts. All cases with severe icing intensity were linked to frontal cloud systems. In homogeneous air masses, 20 percent of which are in the anticyclonic field and baric ridges, light icing was primarily observed. To identify the spatial and temporal localization of potential icing, vertical profiles of temperature and humidity are needed. Usually, these profiles are collected at most sounding stations on the basis of twice-a-day upper-air observations. The number of passes of polar-orbiting satellites over western Siberia's south-east territory ranges from 8 to 16 times a day. Schematic maps of the 2D and 3D-representation of the icing layer itself and its intensity at the same frequency can also be mapped on the basis of first-level satellite processing information and retrieved meteorological parameters in combination with computed methods of icing zone detection. The research was implemented by employing 0.8, 3.9 and 11.03 iim of MODIS and temperature and specific humidity profiles of ATOVS radiometers. Joint study material analysis confirms identification of icing zones using by satellite remote sensing (temperature and humidity). The approach is most relevant for territories in the absence of the upper-air sounding. Given the high probability of aircraft icing conditions obtained by synoptic and statistical analysis, the proposed approach based on the involvement of satellite information will serve as an essential component in ultra-short-term forecasting and nowcasting for the territory of Western Siberia.

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