We now come to the second group of climatic phenomena, pressure and wind conditions. The Ukraine may, in this respect, be divided into two great regions. The line of high pressure which separates these parts, called by Voiekoff the great axis of Europe, extends from the bend of the Volga, near Tsaritsin, over the porohi section of the Dnieper at Katerinoslav to Kishinev. North of this line, west winds prevail, bringing Atlantic air into Northern Ukraine. In the south, east winds prevail, bearing the influences of the Asiatic steppe climate. This wind divide is most distinct in winter. In the northern part of the Ukraine we find chiefly west and southwest winds, which mitigate the frosts and cause precipitations of rainfall; in the southern part dry, cold east winds prevail, increasing the cold. Sometimes the east wind increases to a snowstorm (metelitzia, fuga) which whirls up terrible masses of snow, filling the air with snowflakes until absolutely nothing can be seen, and causes terrific destruction. Herds of a thousand head fall victim to its icy breath, even in the steppes of Crimea, and woe to the traveler who is caught in a snowstorm in the steppe.
In November and December, in Southern Ukraine, moist, warm south winds frequently come up from the Pontus. But the absolute balance is on the side of the freezing east winds, to which is to be ascribed the severe winter climate of Southern Ukraine. The northern half of the Ukraine as a rule, is seldom reached by the east winds, the northwestern corner very seldom. Their occasional appearance is accompanied by heavy frosts with fair weather.
In the spring, east and south winds blow, especially over Southern Ukraine. They often change to heavy sand-storms (sukhovi) very harmful to the crops, which carry clouds of sand, with which they form miniature dunes as high as 30 cm. The east and south winds, at such times, penetrate even into Northern Ukraine, altho with the exception of the northwest corner.
In the summer, on the other hand, the west, northwest, and southwest winds hold a decided balance over the east winds, even in Southern Ukraine. They bring moist Atlantic air and rain into the entire land and mitigate the heat. The occasional east winds increase the heat and bring periods of drought, but usually not until August, when they are rather frequent. In September all the winds are weak thruout the Ukraine, with high pressure. That is why the fall is so beautiful too. Then, in October and November, follows the gradual transition to the winter wind conditions.
The third group of atmospheric phenomena, humidity and precipitation, possesses the same great uniformity in Ukrainian territory as the other two elements of the climate.
The humidity of the air in the Ukraine is in general slight. It is greatest in the forest-covered partly swampy West and Northwest. Toward the southeast the humidity in the Ukraine constantly decreases. Fogs appear seldom and are only light, so that the antithesis to Western and Central Europe, as well as Russia, is striking. The light night and morning fogs which appear, especially in the latter part of summer and in the fall, only contribute to the beautification of the landscape, by flooding the depressions of land like a sea. Cloud-formation is much slighter in the Ukraine than in Western or Central Europe, or in Russia proper, the dreary Muscovite country. The greatest number of clouded days occurs in the western and northwestern part of the Ukraine; toward the southeast and east the number of such days dwindles continuously. The least amount of cloudy weather occurs in the month of August. In September and October the increase is very slight. November and December are much cloudier and January is most cloudy all over the Ukraine. After that the cloudy weather lessens considerably at first, then slowly, until August.
The atmospheric precipitations in the Ukraine are in general insignificant, except in the Carpathian and Caucasus regions. The Ukraine has less rainfall than Central or Western Europe. The Atlantic Ocean, the most important source of the precipitations in Europe, lies far distant, and the cyclonal systems on their way east drop their collected moisture upon Western and Central Europe. For the Ukraine, and particularly for the eastern part of it, there is, therefore, very little left. In this connection the Black Sea has only a local significance, and the evaporation of water from the rivers, lakes and swamps, from the plants and the ground, is hardly worth considering, except as it happens in the summer.