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The climatic and agroclimatic characterization of the winter season 

on the territory if the Republic of Moldova

 

The beginning of the winter season is recorded along with the stable transition of the average daily temperature through 0º towards its decrease, that is noticed in average between 28 November (Briceni) and 13 December (Cahul). Depending on the particularities of the meteorological processes, in some years the winter start date may significantly divert. Although there are times, in average once in 10 years, for the Northern part and once in 4 years for the rest of the territory, when the stable transition of the average daily temperature through 0º towards its decrease is not recorded at all. Since the beginning of observations the earliest winter was recorded on the biggest part of the territory of the country on  9 November 1988. The average length of the winter season in not big and oscillates from 80 days in the Southern part of the republic to 100 in the Northern part.

The average air temperature in winter varies between -1,2º and -3,3ºC.  The coldest winter was recorded in 1953-1954, when the average air temperature was 8-9ºC below zero, that is 6-7ºC lower than the norm. The warmest winter was recorded in 2006-2007, when the average air temperature constituted    1-3ºC  above  zero and  exceeded  the  norm  by 4-5ºC. Since the  beginning of observations the lowest winter temperature was recorded on 20 January 1963 35,5ºC below zero (Brătuşeni village, Edineţ district), and the highest 23,3ºC above zero (Tiraspol) on 26 February 1990. The instability of the air temperature during the winter season is one of the climatic particularities of Moldova.

The coldest winter month is January and its average monthly temperature constitutes 3-5ºC below zero.

During the winter season  there are recorded in average 85-110 mm of precipitations or 16-20% of the average annual amount. The precipitations are mainly in a mixed phase rain and snow, and the maximal daily value was 50-70 mm.

The snow layer (more than a half of the  visible surroundings are covered by snow) on the territory of the country is established everywhere at the end of the first decade of December. Although, in the last years the snow layer may appear only in the second half of January (1959, 1960).

The stable snow layer (that is maintained at least a month) is forming only in  more than 50 % of winter seasons  and only in North and  North-east. On the rest of the territory it is noticed seldom (in 15-50% of the years). The longest period of snow layer maintenance  was in winter in 1995-96. The snow layer persisted for the whole winter season.

Due to very frequent thaw periods the thickness of the snow layer on the territory of the republic is not too high. The mean thickness of the maximal decadal figures during winter  in the opened sectors  constitutes 10-20 cm,  in those protected from wind 10-15 cm. The highest decadal thickness of the snow layer on the territory reached 89 cm (Briceni, second decade of March, 1973).

Usually in winter, the soil freezes and thaws repeatedly and the stable freeze is recorded only in the coldest winter seasons.  The depth of ground freeze does not exceeds 1 m.

Fogs (in average 18-25 days), snow storms (in average 4-9 days), glazed frost and ice deposits (in average 10-18 days) and icy roads (in average 30-50 days) are specific for the winter season.

Among the risk meteorological phenomena the most dangerous are heavy snowing (in average once in 2 years), snow storms  (in average once in 5 years), glazed frost and ice deposits (in average once 3 years).

Generally, the territory of the country has favorable conditions for hibernation of autumn crops, fruit crops and vineyards.

The thawing periods that occur during the warm winters represent a threat for the hibernating crops. Such thawing periods are frequent on the territory of the country. The most dangerous are thawing periods with average daily temperatures  of 5C and higher. During the thawing periods the vegetation of autumn crops and of trees may reassume that can cause their ulterior damage due to a sudden decrease of temperature. Such periods are recorded almost every year. In the Northern part of the country, the number of days with thaws is not high: in 50-70% of years less than 5 days and only in 10 % of years more than 11-20 days. On the rest of the territory the number of days with thaws increases to 5-10 (in 35-50% of years). The number of days with thaws higher than 11-20 is registered in 25-30% of years.

Most often, the trees damage is noticed after long lasting winter thawing periods. This can reduce significantly the resilience of trees to frost. Especially dangerous are the thawing periods from the second half of the winter, because in this period, the trees awake from the profound repose period, reassume their vegetation and therefore the appeared buds may be damaged at 10-15C below zero.

Generally, in winter the autumn crops are is repose. The most unfavorable conditions for autumn crops hibernation occur when the minimal air temperature is 25C below zero and less and when the thickness of the snow layer does not exceed  5 cm. When such meteorological combinations occur, i.e. the minimal temperature at the tillering node depth  decreases to 15C below zero, the tillering node may be damaged or even die, that may cause the death of the whole plant. Such conditions are recorded in less than   5% of the years.

The hibernation of the autumn sowings largely depends on the meteorological conditions during the autumn-winter period, on the resilience of the sowings to law temperatures and on other unfavorable conditions. The well tillered and rooted plants that have passed a good chilling are able to resist to decreases of the temperature up to 16-18ºC below zero.

The hibernation of the fruit crops usually takes place normally.   

The fruit trees crowns and their flower buds  that are hibernating may  resist to frosts up to  25C-30C. The root system of the main fruit crops resists to soil temperatures up to  8-12ºC below zero in the main part of the root (cherry up to 15ºC below zero). Such low soil temperatures are practically not registered on the territory of the country.  

Usually, the vineyards are hibernating well. Generally, during the winter repose the vineyards resist to  temperatures up to 12C below zero, and some varieties even up to 15-20C below zero. In average, the death of the grape buds does not exceed  10-20%.

           

Chief MCMC                   T. Bugaeva   

Chief AFC                      T. Mironova