CLIMATIC CONDITIONS AND RESOURCES. TEXT

The peculiarities of the physiographic location, solar radiation inflow, atmospheric circulation, and underlying surface determine a great diversity of climatic conditions in Ukraine. In its western and northwestern parts the climate is mild with excessive moisture and moderate temperature regime, while in the eastern and southeastern parts there is a deficiency of precipitations and a high temperature background. The diversity of climatic conditions is also associated with the heterogeneity of the underlying surface that varies from plain to mountainous. On the plain, the latitudinal trend of meteorological phenomena is broken by elevations, which is manifested in some reduction of atmospheric temperature, slight increase in rainfall, wind speed, in the change of the snow cover duration, and glaze-ice and rime depositions. In the Ukrainian Carpathians and the Crimean Mountains, a locality altitude and the direction and exposition of slopes determine the vertical zoning of the climate. The considerable length of the coastline has an influence on the climate of littoral regions increasing the air moisture and smoothing the diurnal range of air temperature. The Southern Coast of the Crimea is singled out as an individual region of a subtropical climate.
In the course of a year, climate formative factors manifest themselves in different ways and vary considerably with seasons. In the cold season, the main role is played by the atmospheric circulation, and in the warm season the role of the radiation factor increases.

The climate of Ukraine is characterized by distinct climatic seasons: winter, spring, summer, and autumn.

Winter is the coldest season, bounded by the dates of the stable crossing of the mean diurnal air temperature over 0C in the period of its reduction in autumn and rise in spring. Earliest of all (mid November) it begins in the northeast and gradually spreads to the south and southwest. On the largest part of the territory winter sets in during the third ten-day period of November.

Winter is characterized by the minimum duration of sunshine and the greatest cloudiness (about 75% of the sky is clouded). The total radiation has the smallest values (from 255 MJ/m2 in the northwest to 450 MJ/m2 in the Crimea). In it, the diffuse radiation prevails, which is twice as large as the direct radiation. In winter (DecemberJanuary), the radiation balance is negative on the most of the territory and varies from -80 MJ/m2 in the northwest to -70 MJ/m2 in the Crimea, and from February it becomes positive on the greater part of the territory.

In winter the latitudinal distribution of atmospheric pressure takes place. It reaches the greatest values in January: in the extreme east and west it comes to 1 021 gPa, in the north to 1 020 gPa. On the Southern Coast of the Crimea the pressure is slightly lower.

In winter (January), two zones are distinguished in the distribution of the prevailing wind direction, which lie on either side of the Voyekov axis. North of the axis the wind with a western component is observed, and south of the axis prevails the wind with an eastern component (northeasterly, easterly, and southeasterly), and in the east the northerly wind.

The annual air temperature trend almost coincides with the annual trend of insolation, though is lags slightly behind and is characterized by minor fluctuations from month to month in winter and summer and large swings in autumn and spring. January is the coldest month of the year, the mean air temperature ranges from -8 -7C in the northeast to 34C on the Southern Coast of the Crimea.

Frequent thaws (the maximum air temperature exceeds 0C) are a peculiar feature of the winter season in Ukraine. Thaws are most often in December (to 40%). The minimum number of thaw days (914) occurs in January, while in February their frequency increases again. Most often thaws occur in the southern and western regions. In the Steppe, the number of thaw days amounts to 5060 and reduces to 30 towards the northern east. The maximum air temperature during thaws in the south is 2025C, in the west, 1416C, and in the north, 10C.

In accordance with the general trend of air temperature the lowest values of the annual absolute minimum are observed mainly in January (-42 -26C) and February (-39 -26C).

In winter, the amount of precipitations is the least (3040 mm) but they are rather prolonged. In the Crimean Mountains on the Southern Coast of the Crimea the greatest amount of precipitations is observed, snowfall being the main type. The snow cover forms first in the northeast and in the Ukrainian Carpathians where it lies down usually in the first ten days of November; in the Forest-Steppe, the Crimean Mountains and Peredkarpattia (Forecarpathians) in the second ten days. Towards the end of November, snow covers most of the country. In the south it occurs later: in the Black Sea and Transcarpathian lowlands in the first ten days of December, in the Plain Crimea in the second-ten day period, and on the Southern Coast of the Crimea in the first ten days of January.

In winter, different atmospheric phenomena are observed (fogs, snowstorms, glaze ice, rarely thunderstorms).Winter ends and spring comes first in the southwest and on the Transcarpathian lowland (the middle and the end of the second ten-day period of February); on the considerable part of the territory in mid March; in the extreme northeast, at the end of March. The longest winter (150 days) is in the mountainous regions of the Ukrainian Carpathians. In the northeastern regions it lasts 120130 days. The shortest winter is in the southwest (5060 days), and on the rest of the territory it lasts 90110 days.

Spring starts when the average diurnal temperature stays above zero.

In spring the circulation activity decreases and the role of the radiation factor and underlying surface increases.
Spring is characterized by intensive insolation. The radiation balance in March retains the winter pattern of the territorial distribution and has positive values (from 30 MJ/m2 in the north to 140 MJ/m2 on the Southern Coast of the Crimea). In May it becomes the same as in summer.

In spring the baric field changes and as a result winds of different directions are observed. In the north, east, and south, the easterly and southeasterly winds prevail, in the west northwesterly and westerly, while in the southwest southerly and southeasterly. In March, an average monthly speed has the same values as in winter, from April the wind begins to abate to 25 m/s.

March still has the winter trend of the distribution of the average air temperature. However, from this month it swiftly rises and becomes 35C higher than in February. In the south and west, the air temperature is already positive, while in the north, northeast and in the mountains, it remains negative.

The intensive rise in the maximum air temperature occurs after the final disappearance of the snow cover. In March, it rises everywhere to 20C and in the Crimea to 30C, in April, to 2932C. In May, the record values of the maximum air temperature reach 3235C. The absolute minimum air temperature in May has negative meanings on a considerable part of the territory.

Frosts are peculiar for spring. Especially hazardous are late frosts (in May and early June).

The amount of precipitations in March differs little from that in winter. In April, the transition from the winter distribution of precipitations to the summer one takes place, their amount increases. In spring, continuous precipitations change into downpour.

The weather pattern at the beginning of spring, especially in the first half of March, is similar to the winter one: quite often there are snowstorms during the strengthening of the wind. In spring, the thunderstorm activity begins to develop, most intensively at the end of spring. In some years, droughts and hot winds can be observed.

Spring is the shortest season of the year. It is shortest (5055 days) in the east, where the air temperature rises quickly. On the largest part of the territory, spring lasts 5565 days. In western regions, it is longer (7085 days). In the Ukrainian Carpathians, at the foots of mountains and slopes this period increases to 80 days and to 100 days in the mountains.

Summer is the warmest season bounded by the dates of the stable crossing of an average diurnal temperature over 15C in the period of its rise in spring and fall in autumn. On a large territory summer comes in mid May, in the south, in the first ten days of May, and in the west and north somewhat later. In summer, the insolation and underlying surface become the major climate formation factor. Summer is characterized by a considerable uniformity and stable development of atmospheric processes. The maximum values of the global insolation range from 1 586 MJ/m2 in the northwest to 2 210 MJ/m2 in the western Crimea. The radiation balance reaches the highest maximum values in the south (1 070 MJ/m2) and accounts for 4055% of the total radiation.

In summer, the atmospheric pressure continues to decline. In June, the summer type of wind distribution sets in. July is characterized by northwesterly and westerly winds, and in southern regions, by northerly. The average monthly wind speed in summer is less than in other seasons. In JulyAugust, it decreases to 23 m/s, in mountainous regions, to 45 m/s.

In summer, the air temperature field is stable and uniform, the range of its fluctuations decreases. The mean temperature reaches its highest values in July. From mid August the air temperature reduces to 1720C everywhere except for sea coasts and the Southern Coast of the Crimea (23C). In some years a diurnal air temperature can reach 30C and over, though such rises are short-term.

The absolute maximum is 3840C, it gradually decreases from the south to the north and from the east to the west. Its highest values (3941C) are found in the southern and southeastern regions.

In summer, the greatest amount of rain (6085 mm per month) falls, except for the Southern Coast of the Crimea, where the corresponding greatest values are registered in winter. Heavy showers prevail. The greatest amount of rainfall occurs in June and July, in August it decreases. Summer is characterized by considerable variability of precipitations: the amplitude of their amount can reach 200 mm and more. Sometimes the rainfall is accompanied by thunderstorm, hail, squall, and strong wind. In some years droughts and hot winds are observed.

Summer ends almost on the entire territory in the first ten days of September. The shortest summer (100105 days) is in the extreme north and in western regions. Towards the south, its duration gradually increases to 140 days on the seacoast. The longest summer (150 days) is on the Southern Coast of the Crimea.

Autumn comes in mid September. In the first ten days of September autumn begins in the north and northeast, in central regions, in mid September, in the Zakarpattia (Transcarpathian) lowland, at the end of the second ten-day period of September. In the south, the beginning of autumn shifts to later time the third ten days of September and in the second ten-day period it comes to the Southern Coast of the Crimea.

The role of the radiation factor decreases in autumn. The duration of sunshine considerably reduces. The radiation balance decreases almost fourfold, though it remains positive to the beginning of November and in the late November it becomes negative (30 MJ/m2).

From September, the atmospheric pressure grows intensively, especially in eastern and southern regions. In October, the second maximum pressure is observed, which has recently grown and exceeds the January maximum.
The change of summer synoptic processes into winter ones influences the autumnal wind regime. In northwestern regions the westerlies prevail. Southern regions are the zone of the northerly and northeasterly winds. The average speed increases and ranges from 2 to 4 m/s and in mountainous regions, from 5 to 5 m/s.

The average air temperature from September to November rapidly decreases (by 48C). In autumn, the air temperature lowers quicker than increases in spring. It is associated with a considerable reduction in the radiation balance.

The maximum air temperature is still high enough (about 30C). In November, it remains positive except for the Ukrainian Carpathians. Cloudiness increases and the winter distribution of air temperature sets in. In the third ten-day period of November the average air temperature decreases to negative values almost everywhere.

Early frosts occur already at the end of August in the east and on the larger part of the territory in the second ten-day period of September.

The amount of precipitations decreases in autumn. In September 4555 mm fall in the north; these values decrease to 20 mm on the seacoasts. Types of precipitations change: in September October rain and drizzle prevail, in November mixed precipitations, at the end of autumn solid and mixed. Autumn precipitations are less intensive but twice as long as in summer.

Because of the great variety of weather conditions in autumn, the atmospheric phenomena peculiar for both summer and winter are observed. If in September it still thunders, then in November there are snowstorms. Fogs are one of the characteristic features of autumn. In October, such atmospheric phenomena like glaze and hoarfrost occur but not every year. In November, the first snow cover appears though it does not last long.

On the most of the territory, autumn ends in the third ten-day period of November, while on seacoasts and in the Crimea at the end of December. From this time, a warm period comes to the end and a cold one begins.

In Ukraine, dangerous meteorological phenomena occur, which cause damages in the amount of tens and sometimes hundreds of millions of hryvnias annually.

For the cold season typical are snowstorms, snowfalls, glazes, frosts, and fogs; for the warm one, scorching heat, hot winds, dust storms, great fire risk, intensive rainfalls, thunderstorms, hail, squalls, and tornados.

Dangerous meteorological phenomena are registered annually in every region of Ukraine and often cover large areas. Heavy rainfalls prevail among them.

The Crimean Mountains and the Ukrainian Carpathians are regions where natural meteorological phenomena (heavy rainfalls, hail, strong winds, fogs, snowstorms and heavy snowfalls) recur most often. On the plain, eastern and southern regions and the Crimea are most prone to natural disasters. There meteorological phenomena of both cold and warm seasons are observed.

Global climate changes have an impact upon Ukrainian climate and affect its components. The direct and global radiation have changed under the conditions of moderate cloudiness more than under the fair weather while diffuse radiation has grown both under cloudy and fair weather. The atmospheric pressure has noticeably decreased in January and increased in July. The average wind speed has decreased by 1015% almost on the entire territory. There is an increase in the air temperature in winter and decrease in summer, that is the contrast between winter and summer temperatures has diminished. The amount of precipitations has grown (by 1015%) in the southeast and decreased (by 510%) in the northwest. The increase in the amount of precipitations in the south of the country has resulted in the decrease of the number of dust storms. Because of the great climate fluctuations at the end of the 20th century, extreme weather conditions have become more frequent: especially hazardous are downpours, floods, intensive thaws, early frosts, and increase in the maximum wind speed. Due to global warming, the climate in Ukraine has become softer.

In general, the geographic situation of Ukraine ensures receiving of sufficient amount of heat and moisture and creates favourable natural climatic conditions in its territory.