Vol 10, No 2 (2019)

Two problems in the theory of soil thermal conductivity are considered. First, the concept of the thermal diffusivity coefficient is discussed. It was shown that this coefficient can be used for model predictions only in a certain special cases. In the general case (when the soil thermal capacity and thermal conductivity vary in space and/or in time), the thermal diffusivity does not naturally appear. It could be artificially introduced into the heat equation but, in any case, to solve this equation (i.e., to calculate the dynamics of the soil temperature), this one parameter is not sufficient. It is necessary to set both the heat capacity and thermal conductivity as a functions of spatial and temporal coordinates or as a functions of environmental factors (e.g. soil moisture) depending on these coordinates. In this regard, the widespread misconception of the supposed sufficiency of one parameter (soil thermal diffusivity as a ratio of soil thermal conductivity to thermal capacity) for solving the heat equation using numerical methods is discussed. The examples of the common difference schemes used in computational practice show that this is not the case.

Secondly, the condition number for the problem of parameters identification for the dependence of the soil thermal diffusivity coefficient on humidity for one well-known equation is considered. It is shown on real examples, that this problem is often ill-conditioned when solved by the least-squares method. However, sometimes its stability can be significantly improved if simple constraints are set for certain parameters (least-squares method with constraints).

В работе рассматриваются две проблемы, возникающие в теории теплопроводности почв. Во-первых, обсуждается понятие коэффициента температуропроводности в свете того, что оно появляется только в отдельных весьма частных случаях, а в общем случае (когда теплоемкость и теплопроводность изменяются по пространству и/или с течением времени) коэффициент температуропроводности естественным образом вообще не возникает. Для такой среды с переменными (по пространству и во времени) свойствами он может быть искусственно введен в уравнение динамики температурного поля, но, в любом случае, для решения этого уравнения (т.е. для расчета динамики температурного поля) недостаточно одного параметра – необходимо задать и теплоемкость, и теплопроводность как функции пространственной и временной координат или как функции факторов среды (например, влажности), зависящих от этих координат. В связи с этим обсуждается и распространенное заблуждение о якобы достаточности одного параметра (коэффициента температуропроводности как отношения теплопроводности к теплоемкости) при решении вышеуказанного уравнения численными методами. На примерах основных разностных схем, применяемых в вычислительной практике, показано, что это не так.

Во-вторых, рассматривается число обусловленности задачи идентификации параметров одного изветного уравнения зависимости коэффициента температуропроводности от влажности. На конкретных примерах показано, что данная задача при ее решении обычным методом наименьших квадратов часто является плохо обусловленной. Однако иногда ее обусловленность удается существенно улучшить при наложении простейших ограничений на искомые параметры (метод наименьших квадратов с ограничениями).

Текст статьи на русском языке см. на вкладке Дополнительные файлы

The calculating scheme for estimation of ground freezing depth under bare and covered with the snow cover ground surface on basis of air temperature and snow cover thickness is constructed and the example of calculations is performed for the site of the meteorological observatory of Lomonosov Moscow State University for winter periods of 2011/12-2017/18. The comparison of results of estimation scheme and observations indicated good correspondence.

The results of long-term monitoring of soil temperature regime at Bakchar district (Tomsk region) located in the southern taiga zone of Western Siberia are presented. The temperature regimes of peat and mineral soils are compared; their difference is shown. Peat soil has a smoothed temperature dynamics compared to mineral soil. According to monthly average data, in the warm season, the upper 80 cm of peat soil is 5–7 ° C colder than the mineral soil and 0.3–1.0 ° C warmer in the cold season. The increased thermal inertia of the peat soil prevents both its heating and cooling.

According to the circulation seasons [Dzerdzeevsky et al., 1946], according to the website Weather News, extreme events in the Asian territory of Russia for first half of 2019 were considered: daily maximums and minimums of air temperature; maximum daily amplitudes of air temperature, daily maximums and monthly lows of atmospheric precipitation; daily maximums wind speeds, maximum and minimum of snow depths and dangerous natural processes. Their connection with the atmospheric circulation of the Northern Hemisphere has been shown [Atmospheric Circulation fluctuations site… 1899–2018].

In recent years, extreme situations are increasingly becoming apparent in the Asian part of Russia. This attracts the close attention of researchers [Latysheva et al., 2010; Zolina, Bulygina, 2016]. They try to identify the causes of what is happening [Vasilyev et al., 2018; Kononova, 2018; Kochugova, 2018; Tarabukina et al., 2018] and predict the future nature of extrema [Shkolnik et al., 2012]. It seemed interesting to analyze the extremes of the current year (more precisely, the first half of it), to show the real situation today.

The majority of extremes, surpassed in the first half of 2019, refers to the 21st century. This means that extremity has been growing rapidly in recent years. The consequence of this is an increase in the frequency of occurrence of dangerous natural processes.

The main source of information on daily meteorological extremes was Weather News [Meteonovosti.ru]. It briefly informed about fires and floods. More detailed information was taken from local sites [Amur.Info, Taiga.Info, Ulpress.ru, Social media news]. The character of atmospheric circulation was analyzed by classification [Dzerdzeevsky et al., 1946] using data from the site of the Atmospheric Circulation fluctuations.. for 1899 – 2018

The most disastrous flood was June 24 - 29 in the Irkutsk region. It destroyed more than 10,000 residential homes in 98 settlements, 43 schools, kindergartens and hospitals. According to information on July 11, 25 people died.

The strongest were fires in the Krasnoyarsk Territory and the Irkutsk Region in the third decade of July. Smoke from them reached the Ulyanovsk region.

The conducted research allows to draw the following conclusions. The number of extremes of both air temperature and precipitation in the XXI century continues to grow. Negative extremes of precipitation in combination with positive extremes of air temperature lead to natural fires, positive extremes of precipitation - to catastrophic floods. The increasing frequency of atmospheric circulation contributes to an increase in the frequency of occurrence of those and others: an increase in the frequency of occurrence of blocking processes (arctic invasions resulting in the formation of a vast stationary anticyclone) and exits of southern cyclones.