Гордин Владимир Александрович

Localization of satellite data

2022 · CHAPTER · en

When processing satellite information about various geophysical fields, it may be necessary to convert the fields of values averaged by pixels by satellite device into fields of local values on the output geographical grid. Sometimes it is necessary to inverse the transformation of the local values on the grid into a set of pixel integrals. Compact finite-difference schemes provide a higher accuracy order than classical explicit algorithms. In order to convert one type of field into another, it is sufficient to solve a system of linear algebraic equations (SLAE) with a sparse matrix. The transformations are not exact for an arbitrary field, and lead to errors that depend on the grid step and the wave spectrum of the interpolated fields. These errors for different algorithms are compared using the Fourier analysis. The comparison confirms the advantage of compact algorithms for a wide spectral range of waves. The advantage of the compact algorithms is also observed for Gaussian formulas, but in some special way. The grid knots for such formulae are not equidistantly spaced. Additional difficulties in converting one type of field to another exist in the vicinity of the boundary of the computational domain V. Modification of these algorithms is necessary here. For many geophysical problems, the spectral energy distribution of the interpolated fields is known a priori if these fields are interpreted as random. It is useful to apply this a priori information for interpolation to minimize the probabilistic error for a given type of field. Compact finite-difference schemes for these problems also provide minimal error

Fourier analysis of climate change in Russia

2022 · CHAPTER · en

The archive of observations of temperature f(k) at synoptic stations located near major cities of Russia is analyzed. Period: 2001-2020. Observations at the stations are made 8 times a day with a step of 3 hours. In addition, the minimum and maximum temperatures per day are analyzed. At those moments k, when the measurement result for one or another reason did not get into the archive (for example, the checking algorithm recognized this measurement as erroneous), such a measurement is labeled A(k)=0. Otherwise, we assume A(k)=1. We estimate in each year, in addition to the average temperature, the first Fourier harmonic for seasonal and daily fluctuations.

Inhomogeneous anisotropic analysis of the available water content of the upper soil layer according to ground-based and Remote Sensing on the territory of Russia

2022 · ARTICLE · en

The Hydrometeorological Center of Russia receives 2 agrometeorological information from about 950 stations one time 3 per ten days and the remote sensing Advanced Scatterometer 4 (ASCAT) data from three Meteorological Operational (MetOp) 5 satellites. We suggest a combined objective analysis (OA) of the 6 available water content based on the available water content 7 measurements at agrometeorological stations and on remote 8 sensing data. The new version of OA is constructed using two 9 neural networks and the backpropagation of error to learn it 10 simultaneously. The first neural network is used to convert the 11 ASCAT data into the available water content values, and the 12 second network is used to estimate the inhomogeneities of soil 13 moisture fields. We use the optimal interpolation (OI) method 14 for assimilation of the ground-based data. In the new version, 15 we evaluate the correlation functions (CFs) of inhomogeneous 16 non-Gaussian fields, not from sample statistics but from machine 17 learning methods. The method takes into account the combin18 ing of various datasets: ASCAT data, Food and Agriculture 19 Organization (FAO) soil types, European Space Agency (ESA) 20 GlobCover, and National Center for Atmospheric Research 21 (NCAR) climate data.

About some climatic change in Russia

2021 · CHAPTER · en

About some climatic change in Russia.

Технология ежедневного мониторинга влажности пахотного слоя почвы на основе оперативного анализа влагозапаса в почве по данным метеорологических станций и дистанционного зондирования земли

2021 · CHAPTER · ru

Мониторинг почвенной влаги

2021 · CHAPTER · ru

В числе приоритетных задач национальной метеослужбы особо выделяется регулярный и детальный мониторинг условий для роста, развития и формирования урожая основных сельскохозяйственных культур, а также выраженности лимитирующих факторов, включая лимитацию влаги во время засух. Агрометеорологический мониторинг включает в себя наблюдения за температурно-влажностным режимом воздуха и почвы, состоянием посевов и их продуктивностью, наличием и интенсивностью опасных явлений.

Discrete transparent boundary conditions for the equation of rod transverse vibrations

2020 · ARTICLE · en

Local perturbations of an infinitely long rod travel to infinity. On the contrary, in the case of a finite length of the rod, the perturbations reach its boundary and are reflected. The boundary conditions constructed here for the implicit difference scheme imitate the Cauchy problem and provide almost no reflection. These boundary conditions are non- local with respect to time, and their practical implementation requires additional calcu- lations at every time step. To minimise them, a special rational approximation, similar to the Hermite - Padé approximation is used. Numerical experiments confirm the high “transparency”of these boundary conditions and determine the conditional stability regions for finite-difference scheme.

Компактные разностные схемы для аппроксимации дифференциальных соотношений

2019 · ARTICLE · ru

Дифференциальные соотношения включают в себя в частности, как дифференциальные операторы, так и солверы для краевых задач. Получены формулы компактных разностных аппроксимаций дифференциальных соотношений первого или второго порядка вида $P_1[u]=P_2[f]$. Аппроксимация производится на трехточечных шаблонах. Для реализации, как и в случае классических разностных схем, требуется обращение трехдиагональной матрицы, однако, компактные схемы обеспечивают существенно более высокую точность и 4-й порядок аппроксимации вместо 2-го.

Three-dimensional visualization of atmospheric fronts

2019 · CHAPTER · en

We construct atmospheric fronts (AF) – thin surfaces separating generally homogeneous SYNOPTIC air masses using a set of meteorological fields: geopotential, temperature and wind. It can be useful for synoptic 3D analysis of the Earth atmosphere. The analysis can be organized on-line, e.g. during an aircraft’s flight.

Operative Objective Analysis of Productive Moisture Fields in the Top Soil Layer: Day-to-Day Variability

2019 · CHAPTER · en

Soil moisture is one of the components of water balance in nature. Traditionally, during the growing season of agricultural crops, hydrometeorological stations evaluate the amount productive moisture located in the layers 0-10, 0-20, 0-50 and 0-100 cm. We also use information from polar orbital MetOp-A and MetOp-B satellites (and are going to add the information from MetOp-C) with measuring devices – scatterometers ASCAT. Their measurements permit to evaluate humidity in the upper (about 5-cm) soil layer, using remote sensing (ERS). The data is quickly distributed to the meteorological center via the system of data exchange EUMETSAT. We use both types of the information for our daily operative objective analysis (OOA) of soil productive moisture in the top (0-10 cm) and arable (0-20 cm) soil layers, see Fig.1. A considerable part of Russian agricultural areas are located in the European territory, and there is a rather a dense network of Roshydromet stations making observations of the reserves of soil moisture 3 times a month.