The territory of Ukraine is characterized by a marked climatic diversity. Temperate continental climate is predominant almost in the whole of the country (except its southernmost part). The humidity of the air is much higher in the west than in the east. Temperature conditions differ too: they are more damp and mild in the west and more arid and continental in the east. Therefore, for instance, the vegetation period lasts longer in the west of the country.
The climate of Ukraine is determined by its remoteness from the oceans and continental Siberia. Depending on the location of one or another region, it changes from weak continental (west and north-east) to mean continental (east and south-east). Only the narrow southernmost-eastern part of the Crimea is characterized by subtropical climate.
The regular alteration of the influence of wet western (Atlantic) air and dry eastern air in the mostly smooth terrain of Ukraine causes frequent changes in cyclonic and anti-cyclonic activity. In the summer time, this manifests itself in replacement of warm eastern air masses by more wet and relatively warm Atlantic ones. In the winter time, warm Atlantic air masses displace the cold ones that come from the North and Siberia. In some years, considerable deviations in most climatic parameters from the mean of many years are observed.
Atmospheric pressure is an important factor influencing the climatic situation in Ukraine. Anti-cyclones, which are characterized by high pressure, form, in summer, warm clear weather with substantial changes in temperature at day and at night. In winter anti-cyclones are responsible for temperature drop. Characteristic of cyclones is low pressure that is accompanied by precipitation (rain and snow). Anti-cyclones whose influence increases in the eastern and southern parts of the country, come mostly from Central Asia. Cyclones whose intensity is higher in the west, are formed mostly over the Atlantic and the Mediterranean.
Cyclonic activity is predominant in summer in Ukraine, particularly in the west. It accounts for heavy precipitation. In the fall, high pressure prevails in most parts of the country. This leads to the manifestation of Indian summer with clear days and warm weather. In spring, however, hot dry winds often blow and “black”storms strike (specifically, in the south-east of Ukraine).
An area of high pressure develops in winter in Central Asia. Parts of this area, coming through Central Ukraine, reach the Azores and play an important part climatic distribution. They move along the Kharkiv-Kremenchuk-Balta-Kishinev line and are named the Voyekov axis. The latter is the major boundary line of winds in Ukraine. North of it, north-westerly winds prevail. Mostly dry and cold north-easterly winds blow in the south.
The relatively small territory of Ukraine is characterized by substantial fluctuations in temperature and wind conditions.
Winds differ one from another depending upon the season and the region. In winter the influence of Asian anti-cyclone upon the east and south of Ukraine, increases.
In the western parts of Ukraine, westerly and south-westerly winds prevail. In spring, blowing in the steppe areas are mostly easterly winds and in the forest and steppe ones, south-easterly winds. In the Crimea (southern coast of the Black Sea) southerly and south-easterly winds are predominant.
Blowing in summer in Ukraine are mostly westerly and south-westerly winds with the breeze circulation of air masses being widespread in the coastal areas. In the mountains, wind directions greatly depend upon the relief of an area. As a result, so called orographic wind directions prevail in many mountain areas of the Carpathians. In the Crimean mountains stretching from the south west to the north east, winds blow mostly from the north west and the south west.
The speed of winds is of importance where power engineering and energy resources are concerned. In Ukraine, the average annual speeds of winds are the lowest in the Polissya area, but they increase farther in the south. For instance, the average wind speed in Kyiv is 2.7 meters per sec., in Odesa 4.6 meters per sec., in Lugansk 4.1 meters per sec. In winter, as a result of the temperature contrast between southern and northern regions and resultant high baric gradients, wind speed increases to 5 to 8.5 meters per sec. The strength of wind decreases in summer. The average annual wind speed in Ukraine is 3 to 4 meters per sec.
Among the local winds, breezes of coastal areas (1 to 3 meters per sec. – coastal direction and 3 to 5 meters per sec. - sea direction), as well as mountain fans in the Crimean mountains, should be mentioned.
The temperature conditions of the country`s environment play an important part in climate formation. The mean temperature of the coldest month (January) is sub-zero (– 2 to – 7.5°С ) almost everywhere (except the Crimean southern coast). The warmest month in Ukraine is July ( +17.5...+22°С). The frost-free period lasts 260 to270 days (in the Crimean southern part) and nearly 170 days in the country`s north. Considerable deviations from mean annual temperatures are also observed. The absolute maximum of temperatures in Ukraine varies from +36 to +42°С in summer and from +6 to + 18°С in winter. The absolute minimum of temperatures is -30°С in the south and -40°С in the east.
Temperatures change substantially depending on the season and the region. In the south, periods with the mean temperature being above 20° last up to three months. But there are practically none of these in the west and the north. Frosty periods with the mean temperature above О0 С last nearly 2 months in the south and up to 5 months in the north east of Ukraine.
The total amount of precipitation, as well as its distribution in terms of regions and seasons, has a serious impact on climatic conditions in Ukraine. Most rain and snow fall in the Carpathians (up to 1,600 mm per year) and the Crimea (800 to 1,150 mm). In the other areas, this figure varies from 700 to750 mm (in the north west) to 300 to350 mm (in the south east). Such distribution of the amount of precipitation results from the prevalence in the south-eastern regions of Ukraine of anti-cyclones which come from the east, and in the north-western regions, anti-cyclones which come from the Atlantic. In dry years the amount of precipitation decreases noticeably. In the coastal areas of the Sea of Azov and the Black Sea - down to 100 mm, in the steppe areas – down to 150 to200 mm, and the forest-steppe - down to 250 to350 mm.
The balance of humidity and the moisture content of territory is impacted by the relative humidity of air. Its mean annual indicator in Ukraine is 65-70%, and it comes down to 55-60 % in summer. It drops to 10% in especially dry years in summer, in the south-eastern regions. The effect of relative humidity drop in those parts is intensified by frequent dry winds which are often accompanied by dust storms.
Ukraine receives most precipitation in summer. It is only in the Crimea that winter accounts for most precipitation. Moisture deficit, particularly in summer, increases abruptly in the south east and the east. While it is 6 mbar in Lviv (July) , it is 9 mbar in Kyiv, 10 mbar in Poltava, 14 mbar in Melitopol. In winter the whole of the country receives snow which forms (except the Crimean southern coast) a permanent blanket of snow. It is the thickest in February. The thickness of a blanket of snow depends on many factors: the amount of precipitation in the winter, the direction and speed of the wind, stability of the blanket of snow, the types of vegetation, features of terrain. In the wooded Polissya area, the average blanket of snow is 10-17 сm thick. In the southern and western regions, the blanket of snow is restored several times as a result of thaws. Some winters are snowless. In the mountain areas of the Carpathians, the blanket of snow is rather thick (60-70 сm), which does not melt until April - early May.
In summer most regions of the country have mostly dry weather characterized by a high evaporation which by far exceeds precipitation. Moisture in the ground is formed mostly in autumn, winter and spring periods. 30-50 % of all precipitation is of Atlantic origin. Moisture deficit in the ground and the air which is close to it, is a negative factor affecting the crop capacity of the fields in most regions of Ukraine.
Typical of Ukraine is a considerable fluctuation in the amount of precipitation and its distribution across the country and during a year. Such fluctuations are most characteristic of the south of the country. 30-50 % of the annual amount of precipitation can fall here during a month, but there may be no precipitation the same month next year. Periods with no precipitation (especially in the fall) often last 2 to3 months.
In Ukraine three climatic regions are defined, each of which has strongly marked distinctive features in terms of air pressure and temperature, precipitation amount and periodicity.
Considering the influence of relief upon climatic conditions, there are defined four climatic integral regions in Ukraine: Northern, Southern, Mediterranean and Mountainous.
The Voyeykov axis is the climate distributive boundary between the Northern and Southern regions.
The Northern Climatic Region coincides with the Polissya and Forest-steppe areas. It is, in a large measure, under the influence of moist cyclones. The absolute heights of this territory range from 135 to -500 meters. The mean temperature in January is +6.5 to -8°, in July 15.5 to +20.5°, the amount of precipitation is 480 to 690 mm. Also, the continental quality of the the Northern climatic region, just as in the whole of the country`s territory, increases from west to east. Distinguished within this region are the Polissya and Forest-steppe climatic subregions.
The Southern Climatic Region is characterized by a higher level of insolation and greater aridness. It is predominantly influenced by anti-cyclones. The absolute average heights of its territory are not substantial (10-50 meters), January temperature ranges from -2 to -7°С, July temperature from +21.5 to +30°С, the total amount of precipitation is 370-465 mm.
The Mediterranean Climatic Region takes up a small area stretching from the south west to the north east of the Crimean southern coast, and is protected in the north against cold air masses by the Crimean mountains. The climate here is of Mediterranean type. The temperature of winter months is above +1°С. In summer, within 3 to 4 months, the temperature is above +20°С. Spring here is long and warm. Summer lasts nearly 6 months. Autumn is also warm and clear. The mean annual temperature is + 12.5...+ 14°С, the mean January temperature is between -2°С andі -4°С, the July temperature is between +23.5°С and 24°С, the average amount of precipitation is 540-690 mm. Due to this, the Crimea (specifically its southern coast) has most fair climatic conditions for developing a health resort infrastructure of international significance.
The Mountainous Climatic Region includes the Carpathian and Crimean mountains. It is characterized by vertical climatic zones. This is manifested by changes in temperature and humidity depending on height above sea and landscape. The mountains receive much precipitation. (745-1,450 mm). The mean annual temperature here is not high: in the Carpathians it is +4.5°С, in the Crimea nearly +6°. The blanket of snow in the Carpathians stays from October to May. There are forests up to an altitude of 1,600 meters. Beyond are the Alpine meadows with their own distinctions in the Carpathians and the Crimea.
In addition to the general climatic zoning, Ukraine also has a target climatic zoning. It includes above all agroclimatic zoning, climatic zoning for the purposes of construction, transport, heat supply, environmental protection, recreation, etc.
In Ukraine there are four agroclimatic zones. A warm zone with sufficient humidity is situated in the north-western part of the country. The south-east of it stretches a warm zone with medium humidity. The north-western boundary of this zone runs along the Kamyanets-Podilsky – Kyiv – Putyvl line and the south-eastern, along the Znamyanka-Kupyansk line. Farther to the south-east is a very warm arid agroclimatic zone. It includes the northern and north-western parts of Odesa oblast (region), northern regions of Mykolayiv, Kherson and Zaporizhya oblasts, the southern part of Kirovograd and Poltava oblasts, as well as Dnipropetrovsk and Donetsk oblasts. All southern part of Ukraine is the temperate hot arid zone. Ukraine also has the Carpathian and Crimean mountainous regions which, as has been mentioned above, are characterized by distinct vertical zones.
On the whole, Ukraine`s temperate continental, warm and adequately humid climate is conducive to the development of many types of crop and livestock farming (growing of wheat and corn, as well as sugar beat, sunflower, long-stalked flax), horticulture and viticulture (in the south and Transcarpathia). Incidentally, in postwar years sizeable areas in the south (about 200 thou. hectares) were sown with cotton. Many regions in Ukraine are used for providing facilities to build up people`s health and strength and to receive specialized climatological treatment (Crimea, Carpathians, etc.).
Of great economic value is such an energy resource of Ukraine as wind.
Adverse climatic phenomenon sometimes occur in the country. Thunderstorms are frequent in the summer time. The average number of days with thunderstorms is 25 to30 (in the Carpathians, up to 40). Thunderstorms are often accompanied by rainstorms and sometimes, hail. It hails seldom, 1-2 days a year (in the Crimea, over 10 days). Hail often does serious damage to agriculture. Fogs occur 15-30 days a year (in the mountains, up to 130-135 days). In the south, particularly in the Crimea, fogs are a rare phenomenon. In the fall (in the latter half of September) and in spring (May and the first week of June), the invasion of cold air masses causes an abrupt temperature drop in Ukraine (down to -З...-5° С). In some areas, light frosts do damage to agriculture, specifically horticulture and vegetable growing. In winter the ground is covered with an ice crust which can stay several minutes to 10 and more days.Ice cover is 5-10 mm in the mountains, 200 mm). In winter (mostly in January and February) snowstorms occur. They are observed more frequently in the south-east (20-25 days) and less frequently (3-5 days) in the south-west. Snowstorms often do damage to the national economy. There are droughts in spring, summer and autumn seasons. They occur every 2-3 years and cause serious damage to the country`s agriculture. Irrigation, snow accumulation, afforestation and other activities are used in Ukraine to control droughts.In the spring –autumn period, dry winds blow and dust storms strike..
Dry winds normally blow 25-30 days a year, and dust storms occur 3-8 days a year.
Rainstorms often occur in some regions, mostly in the western (15-19 mm per day), northern and central (12-14 mm). In the Carpathians, up to 45 mm of rain fall a day. In a large part of Ukraine`s territory, the maximum amount of precipitation reaches 140-170 mm per day and in the mountains and Alpine plains, up to 200 and 340 mm per day respectively.
The predominantly flat and open terrain of Ukraine directly affects the climatic processes that take place over its territory, causes frequent changes of air masses which come from different parts, bringing here the warmth of the south or the cold of the north, the humidity of the west or the relatively dry air of the east. An exception in this respect are only the small areas in the south of the Crimea and in the Transcarpathia which are shielded against the colder air masses from the north by the Crimean and Carpathian mountains. As a result, these small regions have a microclimate different from the adjacent areas. Characteristic of Ukraine are the most general territorial climatic features: air temperatures increase from the north to the south (in summer, from the west to the east) and relative air humidity, from the esat to the west, as well as from the south to the north.