Low Clouds and Their Forecast at the Airports of the European Part of the Former USSR

E. I. Vetrova, E. N. Skriptunova, and N. P. Shakina

Presented are the characteristics of the regime of low clouds (the ceiling is 1500 m) according to the METAR reports coming from 45 airports in the European part of the former USSR with the temporal resolution of observations of 30–60 min. Computed are the low cloud (LC) frequency in gradations of the amount of cloudiness of 4, 6, and 8 octants, its annual and diurnal variations, the duration and frequency of continuous LC existence for each airport. Studied are the dependences of LC frequency on the weather characteristics at the airport and on the parameters of grid-scale meteorological fields. Obtained are the statistical dependences for the LC forecast at the airports in gradations of 6 and 8 octants. For this purpose, the cluster analysis is carried out and 45 airports are divided into seven groups according to the similarity signs of regime characteristics. The linear dependences of LC presence on the synchronous predictors (temperature and humidity characteristics) forecasted within the frameworks of numerical models are obtained by means of the discriminant analysis for each group. Obtained is the significant skill score of LC forecast based both on the dependent and independent samples (2009–2010). Realized is the technique of computing the prognostic chart of low clouds based on the output data of COSMO-RU7 operational mesoscale model.

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