Influence of frosts on the national economy. First grape Examples of the use of the word frost in the literature
Frost conditions
In the classification of natural disasters in emergency situations, frosts are classified as meteorological and agrometeorological hazards.
Frosts are called lowering the temperature of the soil and / or air to 0 ° C and below at positive average daily temperatures.
Frosts are observed, as a rule, in the transitional season. There are frosts in spring and autumn, early and late.
Weather conditions favorable for freezing (large effective radiation, weak wind) are created in anticyclones and high pressure ridges.
During frosts, the air temperature at a height of 2 m (in a meteorological booth) can sometimes remain positive, and in the lowest layer of air adjacent to the ground, it drops to 0 ° C and lower due to effective radiation.
In the case when the air temperature is positive, and the temperature of the soil or plants as a result of their radiation cooling falls below 0 ° C, frost occurs on the soil.
The intensity of frost depends on the terrain, slope exposure, the presence of a reservoir, forest plantations. It also happens that frost occurs only on the soil, and at a height of, for example, 2 m, there is no frost.
It has been established that during the freezing period, the temperature field is non-uniform both in the vertical and horizontal directions. It is known that at a height of 1-3 cm from the surface of the earth, the air temperature during freezing is the lowest. The temperature difference at the soil surface and at a height of two meters sometimes reaches 2-5°C or more. During radiation frosts, according to our observations, the temperature changes by an average of 1°C for every 15 m of height along the slope.
In the horizontal direction, the temperature field during freezing is cellular. Over one meter, the air temperature in short periods of time can change by 2-3 ° C or more. That is why even small area plants during radiation freezing are damaged differently.
In some years, frosts stop in early spring and begin late in autumn, in others - on the contrary. On the sea coast of Ukraine, frosts often stop before the average daily temperature passes through 5°C.
According to long-term average data, frosts in the air in spring end in the second half of April. Frosts on the soil surface end on average 5-10 days later than frosts in the air.
In some years, frosts occur in the first half of May, and in autumn they begin in early October, in the northern and western regions they are possible in September. In autumn, after the first frosts, a long warm weather.
The length of the frost-free period different regions countries vary widely.
The relief of the terrain has a great influence on the duration of the frost-free period. In hilly terrain, the difference in its duration between the upper and lower parts of the hill reaches 12-13 days, and in mountainous - 20-25 days or more.
Frost types
According to the formation conditions, frosts are divided into:
– radiation;
- advective;
- advective-radiation.
Radiative frost occurs on quiet, clear nights as a result of radiative cooling of the soil and adjacent layers of the atmosphere. The occurrence of such frosts is favored by cloudless weather and light winds. Cloudiness reduces the effective radiation and thus reduces the likelihood of frost. Any screen above the soil surface also reduces cooling. Wind also prevents frost by increasing turbulent mixing, resulting in increased heat transfer from the air to the soil.
The level of radiation frost significantly depends on the landforms. So, in the lowlands they occur more often than in elevated places or on slopes, because. in concave landforms, the nighttime decrease in temperature is intensified, cold air stays longer. Therefore, during radiation frosts, mainly plants located in low places of concave landforms are damaged. Frosts of this type are limited by the duration of the night and usually last 5-6 hours in a row.
Radiation frosts are often local in nature, as they form in lowlands and basins, where cooled air flows from plains and slopes. Frost is unlikely to form in elevated open areas, as cool air flows down from here and is replaced by warmer air descending from above.
Frosts first appear in poorly ventilated hollows and forest clearings. On a cloudy night, on level ground, the temperature can drop to -1°C, while on a forest glade it can drop to -3.6°C.
The thermal properties of the soil have a significant effect on radiation frosts. The lower its heat capacity and thermal conductivity coefficient, the stronger the frost.
Thus, frosts on the surface of plowed soils, which have a reduced heat capacity and thermal conductivity, are observed more often than on the surface of dense soils. This is explained, in particular, by the fact that in soils with low thermal conductivity, the flow of heat to the surface from deeper layers is hindered.
Dense soils, which have a greater heat capacity, cool more slowly at night than loose ones, and with their relatively high thermal conductivity, the loss of heat by the surface is quickly compensated by its influx from deeper and warmer layers.
The darker the soil, the more intense it cools.
Dry peatlands are much more often and more severely affected by frost than wet ones. Peat, as a dark body, on the one hand, is distinguished by a greater intensity of heat radiation. On the other hand, due to low thermal conductivity, heat inflow from deeper soil layers is negligible. Therefore, the surface cooling of the soil and the surface layer of air on peat soils happens to be significant.
The wetter the air, the smaller the drop in temperature at night, so frost is less likely to occur over wet soil than over dry soil. In moist soil, there is a strong influx of heat from deep soil layers.
At temperatures below 0 ° C, water, which mainly consists of plants, freezes, and the resulting ice crystals damage their tissues and cells.
Dense vegetation cools more than the surface of bare soil.
Frost sensitivity changes as plants develop. The most stable withstand temperatures down to -8, -10°C, stable - up to -6, -8°C, low-resistant - up to -2, -3°C, unstable - up to -0.5, -1°C.
Advective frosts are formed during the invasion of cold air masses from the northern regions (longer and more harmful) as a result of advection of air having a temperature below 0 ° C, usually in early spring and late autumn, with full cloud cover and strong wind; may last for several days.
When cold air invades, the soil cools from contact with it, and therefore the air and soil temperatures differ little.
Advective frost covers large areas and little dependent on local conditions.
Advective-radiative frosts are associated with the intrusion of cold dry air, sometimes even having a positive temperature. At night, especially in clear or slightly cloudy weather, this air is additionally cooled due to radiation and frosts occur both on the soil surface and in the air. These frosts are the most dangerous.
Advective-radiative frosts are observed in a limited time, mainly in the morning or from half of the night and last 3-4 hours. These are late frosts of spring and early frosts autumn, i.e., the time of year when the level of average daily temperatures is relatively high. When they occur, the processes of advection and radiation complement each other. Negative values temperatures can only be in the subsoil layers, while at the level of the meteorological booth they are positive.
Freezing often causes great damage to the national economy, especially agriculture, hitting orchards, orchards and vineyards.
Advective frosts in spring cause significant damage to orchards and berry fields, vegetable and field crops.
The most dangerous are advective-radiation frosts formed late spring or early autumn, after a long warm period.
Frosts are considered weak when the air temperature on the soil surface drops from -0.1 to -2°C. layer of air with negative temperatures from 0.5 to 2 m, above the temperature is already positive.
During moderate frosts, the temperature on the soil surface drops to -2.1 - -4°C.
Below -4°C and up to -7°C - strong and very strong frosts, and even lower - already frosts.
Meteorologists distinguish three types of frost.
advective- arise from the invasion of cold air from the north. They can last several days, cover large area and little dependent on local conditions.
Radiation- due to the cooling of the soil on clear days. With such frosts, the temperature of the soil surface and in the surface layer can be 3-4 ° C colder than at a height of 2 meters from the ground (at such a height the air temperature is measured at meteorological stations), and the most low temperature happens before sunrise. The intensity of freezing is strongly influenced local conditions: site height, slope, vegetation, soil density and moisture, and even soil color. At night, in the lower parts of the slope and in the valleys, it is much colder than in the upper and at the top. In closed basins, the temperature difference at the soil surface and at a height of 2 meters can reach 10°C. In the forest, the temperature is higher than in the clearing, by 2-3 °. Dry and loose soil has low thermal conductivity and heat capacity, therefore, it contributes to the occurrence of radiation frosts, moist and dense soil, on the contrary, reduces the effect of frost. On the eastern and southeastern slopes, plants are more damaged because they are exposed to the sun in the morning.
Advective radiation- are formed from the invasion of cold air and further night cooling of the soil.
It is impossible to predict in advance when they will appear. Usually about a sharp cold snap in spring and autumn periods reported in weather forecasts with a lead time of 1-3 days. During this time, you can take the necessary measures to protect plants.
All methods of protection against radiation frosts are the most effective. These include: smoke- raises the temperature by 1-2°C, film cover increases soil heating by 7-10°C, soil moisture increases its thermal conductivity and heat capacity, and moisture condensation contributes to an increase in temperature in the surface air layer by 1.5-2°C. Dark mulch increases soil temperature by 2-3°C, while light mulch lowers it by 4-8°C.
Loosening the soil to a depth of 2-4 cm reduces the temperature in this layer by 1-3°, and rolling increases by 1-2°. Even small ridges turn out to be 2-3° warmer during radiation freezing.
Highly good effect during radiation freezing gives blowing air, but this technique is available only for large specialized farms.
The simplest approach is powdering seedlings with earth.
In general, to protect plants from frost great importance It has the whole range of measures: selection of precocious and winter-hardy varieties, making potash fertilizers, taking into account the microrelief, observing the sowing dates, etc.
One of the favorite tasks in applied physics of the remarkable engineer and teacher Semenov Vitaly Ivanovich is related to frosts. This term has been heard by any of us, but even people who are well versed in thermodynamics often cannot explain the physical meaning of this natural phenomenon. Moreover, the statement of the problem sounds quite clear:
"Task #1. Determine the method of heat transfer in the process of “falling out” of frosts on the ground. Those. determine how the dew froze on the ground, grass and trees. At the same time: the air temperature during the next day did not fall below 0 ° C. Additional clarification: frosts (the most characteristic) occur on calm and cloudless May or August nights.
“Task number 2. Suggest at least three different ways frost protection.
It is interesting to observe how these problems are divided into parts, recalling the first law of thermodynamics 1 , and the definition of heat 2 , and methods of heat transfer 3 along the way, and still do not find the correct answer.
The meaning of the term FROST.
frost (matinees) - lowering the air temperature on the surface of the soil and plants below 0 ° C at positive average daily air temperatures.
There are advective, radiation and advective-radiation frosts.
Advective Freezes.
The name comes from the word "advection" - delivery, invasion. Advective frosts occur as a result of the onset of waves of cold arctic air with temperatures below 0 ° C, usually in early spring and late autumn, with full cloud cover and, therefore, wind strength; may last for several days.
Effective means of control against this species spring frosts no, because in this case cold air masses affect plants for a long time. Fortunately, there are such spring frosts, mainly in northern regions, where the dates of sowing (planting) garden crops are later than in middle lane or in the south.
Radiation Freezes.
The earth's surface is heated by direct solar radiation. In addition, the atmosphere heated by scattered radiation gives off part of its heat to the soil. The earth receives heat from solar radiation and the atmosphere and, in turn, emits thermal energy in environment(long wave radiation). Radiative spring frosts occur before sunrise in clear and calm weather at relatively low average daily temperatures and intense night radiation. Long-wave radiation of the earth increases, the soil surface cools rapidly. Their level significantly depends on the landforms. So, in the lowlands they occur more often than in elevated places or on slopes, since in concave forms of relief the night temperature decrease is intensified, cold air stagnates longer. Therefore, during radiation frosts, mainly plants located in low places of concave landforms are damaged. Frosts of this type are limited by the duration of the night and usually last 5-6 hours in a row.
Spring frosts damage leaves, blossoming buds, tops of shoots, grape inflorescences, autumn frosts- leaves, sometimes berries.
Hidden spring FROST.
Hidden spring frosts are quite rare and usually precede another type of spring frost - radiation. In this case, the temperature on the surface of plants drops below zero degrees at a positive ambient temperature.
Advective-radiative FROST.
Advective-radiative frosts are formed as a result of the intrusion of relatively cold air and its further cooling due to night radiation.
Opposition radiation frost.
Active countermeasures frost - heating the garden area with gas or liquid fuel burners, the use of powerful fans for moving air layers or continuous , shelter of heat-loving plants and soil around them with a film or nonwovens, abundant watering on the eve of frost, mulching the soil with organic materials. In small areas in calm weather, smoke can be effective.
Above an area with well-moistened soil, when the air temperature drops, condensation occurs, accompanied by heat release. A vegetable garden, covered with a cloud of water vapor, may well withstand a radiation spring frost. Moist soil retains heat much better. Early in the morning, the surface temperature of moist soil is at least 1 degree higher than dry soil. Irrigation, sprinkling, construction of ponds, reservoirs, irrigation systems to change the microclimate on drained peatlands are of strategic importance for protecting crops from frost (in conditions of drained peatlands), which will reduce the night temperature drop by 8-10 degrees.
P.S. I guess everything is in place now. Radiation frosts, namely, they were discussed in the task, occur due to the radiation of the Earth into outer space. Similarly, the Earth receives energy from the Sun. It is curious to note that all methods of dealing with radiation frosts are based on three methods of heat transfer. In some cases, they try to compensate for heat loss by heat transfer between the soil and the water film or humid air. In others, to eliminate radiation by organizing protective screen as polyethylene film, smoke or fog. In the third, they provided intense convection ...
P.P.S. I hope you enjoy these puzzles. Once again, you can see how ordinary everyday phenomena can be mysterious and amazing ...
P.S.P.S. I propose to independently solve three more problems: 1) how does fog form after rain? 2) How is morning dew formed? 3) how does frost form on trees in winter?
Temperature drop air on the surface of the soil and plants below 0 ° C at positive average daily air temperatures.
There are advective, radiation and advective-radiation frosts.
advective frosts
arise as a result of the onset of cold waves with temperatures below 0 ° C, usually in early spring and late autumn, with full cloud cover and, therefore, wind strength; may last for several days.
Radiation frost
occur on quiet, clear nights as a result of the daily temperature variation at relatively low average daily temperatures and intense night radiation. Their level significantly depends on the landforms. So, in the lowlands they occur more often than in elevated places or on slopes, since in concave forms of relief the night temperature decrease is intensified, cold air stagnates longer. Therefore, during radiation frosts, mainly plants located in low places of concave landforms are damaged. Frosts of this type are limited by the duration of the night and usually last 5-6 hours in a row. For grape culture, spring frosts are most dangerous if they occur in the second phase of the growing season. Advective-radiative frosts are observed in a limited time, mainly in the morning or from midnight and last 3-4 hours. These are late frosts of spring and early frosts of autumn, that is, the time of year when the level of average daily temperatures is relatively high. When they occur, the processes of advection and radiation complement each other. Temperature values can be negative only in the subsoil layers, while at the level of the meteorological booth they can be positive. Spring frosts damage leaves, blossoming buds, tops of shoots, grape inflorescences, autumn frosts damage leaves, sometimes berries. Frost control means have been developed, which can be combined into 3 groups: selection of frost-resistant grape varieties. Their stability is associated with the peculiarities of the varieties to open their eyes later and bear fruit from spare buds in the eyes; agrotechnical impacts on grape bushes: late spring pruning(to delay bud break) and leaving a segment of the stepson with 1-2 nodes at the eyes, followed by a fragment of the shoots grown on these stepchildren, the use of high-stem forms of bushes; agrotechnical impacts on the environment in order to reduce radiation through the destruction of weeds.
During radiation frosts, according to our observations, the temperature changes by an average of 1°C for every 15 m of height along the slope.
In the horizontal direction, the temperature field during freezing is cellular.
Over one meter, the air temperature in short periods of time can change by 2-3 ° C or more. That is why even in a small area, plants are not equally damaged during radiation freezing.
Fig.1. Graph for determining the probability of a frost (matinee) on the air temperature at 21:00 and on the temperature difference at 13:00 and 21:00.
A warning about the possibility of frost on the territory of the region, its individual districts is given on the basis of forecasts made in the institutions of Roshydromet. But will there be frost on a particular garden plot an amateur gardener can clarify using his own observations. The degree of possible overnight cooling to frost is predicted in many ways. The simplest is the method of P. I. Brounov.
For calculations by this method, the air temperature is measured at 13 o'clock (in the shade) and at 21 o'clock. Find the difference between these indicators and make simple calculations.
For example, the air temperature at 13:00 is 9.5 °C, and at 21:00 it is 3.3 °C. The difference between them is 6.2 °C. The calculation is performed according to a special schedule (Fig. 1). On it, the difference between day and evening temperatures is plotted horizontally, and the air temperature at 21:00 is plotted vertically. °C. Then we draw straight lines to the right (from the vertical axis) and up (from the horizontal axis) until they intersect with each other. The point of intersection of the lines will be denoted by the letter A. It lies below the sloping straight line, showing a 100% probability of freezing, from which it follows that there will be a frost.
One more example. At 13:00 the air temperature is 12.3 °C, and at 21:00 it is 10 °C. The difference between them is 2.3 °C. We find the point of intersection of two lines (the construction is similar to that described above). This point will be denoted by the letter B. The graph shows that the probability of freezing is about 18%. Therefore, frost is unlikely.
For the most part, they are very tender and at -2 ° C they can already be damaged. In this regard, it is very important for gardeners to know how to protect their garden from such a natural phenomenon.
What's this?
The essence of frost is temporary drop in temperature air in a particular area. They come in autumn and spring.
The reasons Frost may occur as follows:
- migration of cold air from the northern regions to a given place;
- the result of a nightly decrease in temperature (radiation).
If frosts are associated with radiation, then the weather is usually clear and calm. Such a decrease in temperature is always short-term and almost never reaches such a force that manifests itself during return spring coolings.
The latter, on the contrary, can last for several days, cover a larger area and are additionally accompanied by cloudy skies and strong winds.
Did you know? In 1558, such a severe cold set in Europe that, which was stored in French cellars, froze. They began to sell it at that time not on tap, but in ice blocks - by weight. The situation repeated itself in 1709. During the chimes of the bells in the temples, the latter even cracked.
Freeze types
Frost is a decrease in temperature below 0 ° C, mainly at night and in the morning. At the same time, the average daily temperature remains positive. They are divided into three types: advective, radiative and mixed.
advective
The cause of advective frost is air mass migration moving in the horizontal direction. They bring with them cold temperatures, humidity, etc. Such colds come on suddenly and then last for a long time. 
Radiation
Radiation frosts can be explained with the help of physics. During the day they accumulate heat, and at night they give it away.
Because the warm air lighter than a cold one, it rises, and cold air masses take its place. Naturally, the lower the soil temperature, the more dangerous the consequences will be for the plants. Such cooling can usually be observed in cloudless and windless weather, they can capture a fairly large area.
Advective radiation
As the name implies, this mixed type cooling. A weak frost is considered to be a decrease in the temperature on the soil to -1 / -2 ° С. If it gets colder to -3 / -4 ° С, then such a frost is called strong. A very strong frost is -5 / -8 ° С.
The effect of frost in spring and autumn
Frosts, namely the features of their manifestation on horticultural and horticultural crops, directly depend on frost resistance the latter - the level of critical temperature, at the onset of which the organs of the plant are partially damaged or die. Frost resistance differs not only different plants, but also organs of the same plant or vegetable crop. 
If a return frosts come early, then they may not have time to harm the plants, because the latter have not yet had time to germinate, which means they remain under the protection of the soil and. More dangerous are late return drops in temperature, which can manifest themselves until the beginning of June. They just fall into the period of flowering and crops.
Young leaves, buds and flowers are very sensitive to cold and cannot yet resist it. The juice in the cells freezes, as a result of which the membranes rupture and death of the cells occurs, and then the plants themselves.
Did you know?Abnormal winters on the planet were observed long before the invention of thermometers. According to the chronicles, in the winters of 401 and 801, "the waves of the Black Sea hardened."
For garden crops
Even with minimal temperature drop get seriously hurt maybe loosely rooted and not yet hardened seedlings, heat-loving and. An indicator of -1 / -2 ° C is enough for the plants to stop their growth, and fruiting is delayed by 1.5-2 weeks.
If the frost is more severe, the culture may die. Always the first to suffer are those crops that are planted in the ground close to the surface. This, etc. 
But still there is horticultural crops who are not afraid of cold snaps. it cold-resistant plants that are not damaged due to a drop in air temperature. These include, and even.
For fruit
Fruit trees are almost always sensitive to frost. Even when the temperature dropped completely a short time adverse effects may be irreversible. As observations show, the earlier warm weather sets in, the higher the likelihood that late cold snaps will manifest themselves.
most dangerous for fruit trees are the conditions when the day temperature regime remains within 5-10°C, and at night it drops to -2 °C. In this case, the flowers will already receive irreversible damage. As for the ovaries, they can die even at a temperature of -1 ° C. 
It happens that after freezing, the ovaries and flowers remain in their places, do not crumble, and it may seem that everything worked out. But unfortunately, quite often, low-quality fruits with pronounced deformation grow on such trees, and the overall yield is relatively low.
Most affected by frost, and gardens. As for, they bloom a little later than others. horticultural crops and damage a little less than the rest. Reduce harmful effects frosts are helped by being close to trees, as the water gives off heat at night and thus warms the plants a little.
Ornamental trees and shrubs
Speaking of and, it is worth noting that the former are more susceptible to damage than the latter. This is due to the fact that at the level of the crowns, air temperatures are usually higher than at the bottom. With light frosts, it may happen that they can be damaged, and at the same time no harm will be done to the trees.
Separately, it is worth talking about whether spring frosts will be detrimental to roses. If the protective one was removed from the flowers before, then the branches can freeze at temperatures below -7 ° C. In the same case, the leaves and buds will definitely freeze. Such an impact will weaken, slightly delay the time of flowering, but will not destroy it. 
In order to die, frosts must greatly cool the soil so that the roots have time to freeze through, and this practically does not happen in spring. Weak frosts in the range from -1 ° C to -3 ° C usually do not affect in any way or cause very little damage.
What to do? Frost control methods
There is a lot of talk about methods of dealing with frost. Some methods have proven to be very effective, while others are very dubious, time-consuming and do not bring results.
Sprinkling
The method is quite interesting. It will also take a small one so that the jet resembles raindrops. Trees and shrubs need to be completely watered. And as the water freezes, it will begin to release heat, which will be saving for the plant.
At temperatures closer to 0°C, the liquid evaporates and forms vapor, which has a high level of heat capacity. This method is also suitable for . Watering should be done in the evening if frost is expected at night.
smoke
This method should be applied immediately after the air temperature has dropped to + 2 ° C. Smoke must be carried out before dawn.
Smoke should spread along the ground, only in this case it will help protect the plants from frost. This is due to the fact that its temperature is higher than the air temperature, which means that the smoke will become an obstacle to cooling the soil surface.
It is thanks to this that plants will be able to survive a sharp cold snap. It is desirable that during the smoking process there was calm weather. Otherwise, you need to carefully monitor the absence open fire to avoid fire.
By the way, during spring frosts for smoke, according to gardeners, is the best protection.
The process itself is carried out as follows:
- Along the perimeter of the site, you need to collect heaps of straw, garbage, and other material that will later become a source of smoke.
- Then a stake should be driven into the ground, which will serve as a support, and dry material should be laid around it, which will ensure combustion.
- What ignites quickly should be covered with sawdust, leaves, damp