The article presents a detailed pattern of the spatio-temporal distribution of the De Martonne aridity index in Ukraine. The distribution of climate types by this indicator at the weather stations of Ukraine is also presented. The De Martonne aridity index has been statistically analyzed at 187 weather stations in Ukraine. The dependences of De Martonne aridity index on the elevation of the station above the sea level, its geographic latitude and longitude were estimated. The overall contributions of each of these characteristics to total variance of this indicator were also evaluated. Scatterplots of the index of aridity depending on location's coordinates are presented. The long-term trend of this indicator for the period from 1931 to 2010 has been studied on the example of weather stations that represent the plain part of Ukraine: Lviv (west), Kyiv (north), Poltava (east), Uman (center) and Kherson (south). It has been shown that the humidification regime of Ukraine for the period under consideration has insubstantially changed, but the tendency towards aridization is still prevailing. This statement is fully consistent with the results of previous studies. The map of De Martonne aridity index for the standard climatological period 1961-1990 and modelling results of its geographical distribution using linear regression equations are presented. It was noted that the three-factor model of multiple regression this indicator for the plain stations of Ukraine may have the greatest theoretical value. The average absolute error (2 units) and average relative error (6.2%) of the estimation of the De Martonne aridity index were determined. It was established that the dynamics of the De Martonne aridity index over the past 50 years has been consistent with the dynamics of the change in the hydrothermal coefficient of Selyaninov. It was concluded that climate of Ukraine has a weak tendency to increasing of aridity, which has certain risks to development of agricultural sector.

No abstract

Introduction. This paper deals with the specific aspects of insolation of the terrestrial surface in the southern regions of Ukraine, namely the clearness index and diffuse fraction of the atmosphere. The study was based on satellite data of the average daily insolation and total cloudiness in the nodes of the two-degree grid for the domain with coordinates 48°-45° N and 29°-39° E for the period of 1981-2020. The purpose of article. The purpose was to develop statistic models of horizontal surface insolation for various locations of study domain. Main focus was put on special characteristics in conditions of fixed cloudiness. Satellite data for the summer season had been used to evaluate the maximum solar energy potential of Ukraine. Methods. Application statistical analysis and means of cartographic data layout were used in the paper. Results. It was found that with the highest (more than 50%) frequency the total cloud cover can be characterized by the atmosphere clarity corresponding to a clear sky condition. The significance of irradiation of the terrestrial surface with diffuse solar radiation has been observed, with the share of such radiation in the global irradiation (diffuse ratio) being closely inversely related to the clearness index (correlation about -0.97). In turn, both diffuse ratio and clearness index are statistically dependent on the sky clarity, that allowed deriving analytical functions - diffuse ratio and clearness index - of the sky clarity, which appeared to be S- and Z-shaped curves, respectively. Dispersion of the clearness index ( ) and the diffuse fraction ( ) values and the strength of their statistical relationship significantly depend on the sky clarity. The empirical distribution of the two-dimensional random variable ( ; ) well meets the Gaussian distribution, and the obtained dispersion ellipses allowed calculating the confidence intervals of the two-dimensional random variable (clearness index: diffuse fraction) for a given confidence level. The spatial distribution of the clearness index and diffuse fraction of the atmosphere in the southern regions of Ukraine revealed a significant dependence of these indices on the latitude and the type of underlying surface. At the end of the summer a seasonal effect has been observed in the spatial distribution of the clearness index and diffuse fraction, which can be explained by the specific seasonal features of atmospheric circulation, caused by the spreading out of the eastern ridge of the Azores anticyclone and the general situation with blocking developments in the Atlantic-European sector of the Northern Hemisphere. The scientific novelty. Correlation and regression models of special insolation characteristics in conditions of various cloudiness that are represented in this paper are new to Ukraine. Analysis of two-dimensional random value spread (clearness index: cloudiness index) allowed to assess probabilities of integral solar radiation flows. The obtained analytical membership functions for monthly average values of clearness and cloudiness indices depending on the level of sky clarity proved to be applicable for determining respective indices for daily time scale. Practical significance. The obtained results are important for comprehensive assessment of the solar / photovoltaic resources of southern regions of Ukraine. Specifically, analytical dependences have practical values for the purpose of forecasting direct and diffuse solar radiation in various time scales based on publically available global records of solar radiation.

Principles of constructing of indicators of thermal oceanicity of climate are considered. Some of them are statistically grounded to describe continentality or oceanicity of Ukrainian climate. Maps of the difference between the average temperatures of September and May, the annual air temperature range and their percentages over the territory of Ukraine as a particular index of oceanicity of climate are constructed. Effective models of multiple regression of the considered variables are constructed depending on the components of the geographical location. It was found that weather station altitudes reveal a significant effect only on the annual air temperature range. It was determined that the contribution of geographic longitude in the total variance of this variable is 44.2%, latitude – 37.4%, altitude – 18.4%. Two-factors regression models are constructed for other indices. They included only the geographical coordinates of weather stations. Determination coefficients of equations of multiple regression are in the range of 0.75-0.80. It was determined that all regressive models are statistically significant at the 1% significance level. It was established that the thermal influence of the Black and Azov seas on climate of Ukraine extends to about 47-48 parallels.

No abstract