Conditions of squall formation in the south-eastern territory of Western Siberia

In this paper the atmospheric instability parameters during a squalls day in the south-eastern territory of Western Siberia are considered. The information on parameters of the atmosphere condition during squall days was taken from the data of atmosphere aerological sounding for the station of Novosibirsk at 00 and 12 o'clock of the Universal Coordinated Time from May till August 1991-2008. The atmosphere condition for 79 days when squalls were registered was analyzed. The parameters of instability obtained from sounding of atmosphere contain information on pressure and air temperature rates at the level of condensation; thermodynamic characteristics of the atmosphere condition; humidity and the wind shear in the layer of 1.5 to 5.5 km high; the height of levels of condensation and convection; the convective potential energy of atmosphere and the energy of the inhibition layer. For each day when squalls were observed over the south-eastern territory of Western Siberia the values of nine parameters of the atmosphere condition were analysed: LIFT, SWEAT, KINX, TOTL, CAPE, CINS, LCLP, EQLV and BRCH. Atmospheric instability parameters were used to indicate the convection development degree. The discriminant, statistical analysis was made. The potential was estimated to use these parameters for making alternative forecasts of squalls development in the investigated territory. The results were compared with the indexes values obtained by other authors. Most part of squalls was formed in the atmosphere condition which is considered to be a moderately unstable one (by foreign researchers). No more than 2 % of all squalls were observed at the extremely unstable atmosphere condition. It means that conditions of squalls development differ in different regions; therefore, for the south-eastern territory of Western Siberia updating of threshold values variability of parameters corresponding to certain degrees of atmosphere stability is required.

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