The atypical winter for the recent years but absolutely typical for our climate and geographical location, does not cancel the climate change resulting from the global warming. On the contrary, this evidences that the ongoing changes are not simple.

Climatic forecasts (climate change scenarios) just envisage that the global temperature growth is causing and will cause phenomena not observed in the certain geographic area before. More frequent will become weather phenomena, first of all adverse ones, which have been extremely seldom or absent before. This also concerns the current, cold, snowy winter in West European countries. In particular, a very cold weather is in the United Kingdom, where severe frosts were registered this winter. Besides, there fell much snow that is not typical for this country’s safe and comfortable climate.

This winter’s amount of snow also appeared unusually large in other countries of Europe, including Ukraine. The reason is extremely active cyclones. The increasingly fluctuating climatic system contributes to increasingly unstable weather.

Conclusions of the world’s climate change experts were confirmed that the Global climate change shows itself not merely in rising average temperatures, but first of all in increasing quantity and intensity of single adverse phenomena.

This winter’s cold weather is in many respects caused by large amount of snow. The snow cover, which we used to consider warm and which saves plants and animals from frost indeed, in large scale, contributes to significant cooling of the planet. Reflectance (albedo) of snow will isolate large areas from sun rays for long. For example, sun heat coming in moderate latitudes on clear March days is quite enough to warm and melt the soil and to warm the adjacent air layer. However, while snow lies on the ground, the soil remains frozen and the air cold, and the snow itself melts very slowly.

“Snow in the field means grain in the barn” – this old proverb very precisely describes the role of snow in farming. The soil’s temperature, humidity, chemical composition, structure, and saturation with microorganisms considerably depend on the thickness of snow covering it in winter and on snow properties. The most significant role is played by snow in arid areas, where it is the main source of moisture reserves needed for plant growth. Different methods are known for capturing snow in the field: gathering it into ridges, compacting by rollers, leaving high field stubble in the fall, screens in winter crop fields etc. This produces a very appreciable effect. 35 - 40 cm of snow gathers in high stubble or between ridges, while just 8-10 cm is seen nearby where those are absent. This difference gives additional 800-900 m3 of melt water per hectare and contributes to higher yields.

The snowpack is an extraordinarily rich moisture reserve and simultaneously an interlayer between the earth’s surface and the atmosphere. Even a thin snow layer generates a sort of “snow” climate. A cold, snow-free winter is a real natural disaster for many regions. When the soil temperature at the 3 cm depth (where tillering nodes of winter crops are located) reaches 17 - 20° below zero, almost all plants die. When the snow layer amounts just to 20 cm, the temperature at this depth does not drop below -10-12° any more. Most plants on our territory easily withstand such a cold snap. 40-50 cm high snow drifts guarantee that even the severest frost (even to 35-40° below zero) will not cause the soil temperature to fall below -8° and all plants will safely survive the winter.

Besides, melt water contains various chemical admixtures: chlorides, sulphates, hydrocarbonates, and nitrogen compounds.

The snow cover distribution trend looks very interesting in the global warming period. The results of joint studies of Finnish and Russian scientists on European snow distribution were published in 2006. These studies revealed an upward trend in the duration of snow cover in Northern Europe against the background of rising air temperatures in the cold season.

And this conclusion does not contradict the warming conditions. As the air temperature goes up in this region, cold-season precipitation rates increase, as well as its snow reserves.

In the past 20 years, 70% of Ukraine’s winters were featured by a largely insignificant snow cover. 2 years with heavy winter crop losses were registered during this period. In 2003, adverse wintering conditions killed about 70% of sown winter cereals and almost 100% of rape crops. These conditions included early winter frost without any snow cover and a long exposure to an ice crust after then.

In 1994, the percentage of lost winter crops reached almost 35% of their overall acreage. The reason was a long severe frost in February following an intense thaw, while almost no snow covered fields.

Thus, the snow cover is extraordinarily important for safe wintering of crops in Ukraine.
 

Lost crops due to winter weather conditions

 
A snowpack formed in fields in December as a result of a series of active cyclones. Naturally, its height changed during the winter, but it nevertheless covered fields with a continuous layer as of early February.

In December, the average monthly temperature was close to normal and there were seen actually no adverse phenomena affecting the wintering process. A few waves of severe cold were observed, due to which the average monthly air temperature appeared 2-5° below it normal level despite an intense thaw at the first half of the month. 

The lowest air temperature in January reached -20-25° in the Southern regions and -26-30° in the remainder of the country. The lowest air temperature (32-34° below zero) was registered in the Lviv and Ivano-Frankivsk regions. They were not the lowest in the past 50 years. The January air temperature dropped to 35-37° below zero in the East and West in 1963, 1970, 1987 and 2006. In the cold January of 1987, the air temperature fell to -40° in the Kyiv and Sumy regions.
 

Depth of snow cover

 

Thanks to the snow layer covering fields in both December and January, wintering crops were not jeopardized in most parts of the country. Only at the coldest time, on January 21-31, a soil temperature decrease to -15-19° at the 3 cm depth was registered in the northern districts of the Kharkiv, Luhansk, Sumy regions. This might have caused partial winter kill of winter wheat crops remaining underdeveloped since the fall.

A soil temperature decline to -11-14° at the 3 cm depth was observed in the Kherson, Zaporizhzhia, Odesa, Poltava regions. This drop may result in local damage to less frost-resistant plants of winter barley and is extremely dangerous for winter rape.

The analysis of long-term observations shows that this type of winter will most likely lead to a moderate progress of spring processes, even to a slow one in the Western regions. This will result in a late beginning of the spring field works – not sooner than the latter half of April. The favorable period for sowing (in view of the combination of optimum soil moisture and temperature) will be short.

This winter’s high, persistent snow with insignificant freezing of the soil is an extraordinarily favorable factor for the accumulation of sufficient moisture reserves for spring, especially taking into consideration a severe drought observed in Ukraine in the fall.

Tatyana Adamenko, specially for UkrAgroConsult