Next generation weather prediction atmospheric models will have horizontal resolution of about 3-5 km. The problem dimension will be 1010. One will need to use efficiently 104-105 computational cores ...to make a practical operational forecast. This leads to the need for the deep revision of numerical methods and algorithms used in atmospheric models. One of the problems to be solved is the horizontal discretization of atmospheric dynamics equations on the quasi-uniform spherical grids. This problem can be investigated using shallow water model that is much computationally cheaper than the use of full atmosphere model. We are developing an atmospheric dynamics solver for the next generation numerical weather prediction model at the Institute of Numerical Mathematics and Hydrometeorological center of Russia. Within this work, the solver for the shallow water equations using gnomonic cubed-sphere grid has been developed. The solver is verified using standard shallow water test cases. The accuracy of the presented solver is analysed. The good agreement to the reference solutions is achieved, when 4-th order spatial approximations are used.
•Larch stand transpired 24% more water than Scots pine stand.•Stomatal conductance was more strictly regulated in pine than in larch when evapotranspiration demands were high.•Larch transpiration at ...high VPD progressively declined from the beginning to the end of the summer.
Russian boreal forests represent the largest forested region on Earth and comprise one-fifth of the world's forest cover. The two most common genera in Siberia are Larix and Pinus, which together cover more than 80% of the region’s forested area. One observable ongoing effect of climate warming is that natural populations of Siberian larch are gradually being replaced by Scots pine. The present work focuses on comparing effects of environmental variables on sap flow density in two even-aged stands of Larix sibirica and Pinus sylvestris. While the two study stands were identical in age (49 years) with similar basal areas and leaf area index, they exhibited very different transpiration rates and response mechanisms to environmental signals. Stand water use was higher for larch than it was for pine, even though transpiration for deciduous larch trees occurred over shorter time periods. The cumulative annual transpiration of the larch stand was 284 ± 4 mm measured over two consecutive growing seasons (2015–2016), while for pine this was 20% lower. Seasonal transpiration accounted for 50% and 40% of the reference evapotranspiration and 91% and 67% of growing season precipitation for larch and pine, respectively. Water stored in soil provided an important source of water for transpiration, observed as roughly 100 mm, which was then replenished from snowmelt the following spring. The greatest difference between two species related to how well they controlled transpiration, notably in the context of high vapor pressure deficit; under these conditions, pine maintained greater control over transpiration than larch. For all soil moisture levels measured, larch transpired more water than pine. Importantly, our results point to potential future effects of global warming, most notably an increasing decline of larch forests, changes in the ratio between latent and sensitive heat fluxes, and significant modifications in ecosystem water availability.
Climate change projections forecast most significant impacts on high-latitude forest ecosystems. Particularly, climate warming in boreal regions should increase fire severity and shorten its return ...interval. These processes can change the dynamics of boreal forests as younger stands become more dominating with a shift from gymnosperm to angiosperm. However, despite angiosperm's phenological and physiological traits have a high potential for ecophysiological and dendroclimatological studies in Siberia, they have been rarely investigated due to their short-term lifespan in comparison with gymnosperm. Modeling tree growth is a common way to understand tree growth responses to environmental changes since it allows using available experiment or field data to interpret observed climate-growth relationships based on the biological principles. In our study, we applied the process-based Vaganov-Shashkin (VS) model of tree-ring growth
a parameterization approach VS-oscilloscope for the first time to an angiosperm tree species (
Ehrh.) from continuous permafrost terrain to understand its tree-radial growth dynamic. The parameterization of the VS model provided highly significant positive correlations (
< 0.05) between the simulated growth curve and initial tree-ring chronologies for the period 1971-2011 and displayed the average duration of the growing season and intra-seasonal key limiting factors for xylem formation. Modeled result can be valid at the regional scale for remote birch stands, whereas, justification of the local non-climatic input data of the model provided precise site-specific tree growth dynamic and their substantiated responses to driving factors.
We study the microwaave impedance of low-barrier Mott diodes with a δ-doped layer near the metal contact. Parameters of the elements of the diode equivalent circuit are determined and their ...dependences on the dc bias voltage are examined. The effects of injection of electrons into the i layer and their time delay in the potential well of the δ layer under a forward bias are discussed. An original method of the incoming test of epitaxial wafers and the diagnostics of their linear characteristics for the epitaxial structures intended for manufacturing of low-barrier Mott diodes is proposed.
The quality of Arctic winter stratospheric dynamics forecast using the SL-AV atmospheric global circulation model is studied. The series of numerical experiments show that forecasts with the lead ...time up to 7 days are successful. Zonal wind reversal during minor sudden stratospheric warmings is predicted 10–11 days ahead. Overall, the situations of strong polar jet disturbances are beneficial for the forecast accuracy.
The first results on the development of an original power GaAs-based field-effect transistor with a vertical channel controlled by a
p
–
n
junction are presented. The main manufacturing feature is ...the use of two separate epitaxial growth processes when forming the transistor structure. The transistor part containing the drain, drift, and gate regions is grown by liquid-phase epitaxy. Metalorganic gas-phase epitaxy is used to form the channel and source regions.
The work is focused on a numerical hydraulic model, which allows one to simulate fluid flow in a complex, arbitrarily configured multi-channel system with a capability of automatic visualization of ...its structure. The main elements of a system are channels which are united in the system by means of a particular set of coupling elements (local resistance, knots). The processes models in channels are based on the equation of continuity, momentum conservation. The system structure is made by forming matrices of regional and internal boundary conditions according to the developed algorithm. By the model the algorithm is created, on the basis of which the application program is developed. The application program enables one to determine parameters of a steady state of fluid flow in the complex multichannel structures. The calculation structure is shown.
The semi-Lagrangian absolute vorticity (SL-AV) atmospheric model is the global semi-Lagrangian hydrostatic model used for operational medium-range and seasonal forecasts at the Hydrometeorological ...Centre of Russia. The distinct feature of the SL-AV dynamical core is the semi-implicit, semi-Lagrangian vorticity-divergence formulation on the unstaggered grid. A semi-implicit, semi-Lagrangian approach allows for long time steps but violates the global and local mass conservation. In particular, the total mass in simulations with semi-Lagrangian models can drift significantly if no a posteriori mass-fixing algorithm is applied. However, the global mass-fixing algorithms degrade the local mass conservation. The new inherently mass-conservative version of the SL-AV model dynamical core presented here ensures global and local mass conservation without mass-fixing algorithms. The mass conservation is achieved with the introduction of the finite-volume, semi-Lagrangian discretization for a continuity equation based on the 3-D extension of the conservative cascade semi-Lagrangian transport scheme (CCS). Numerical experiments show that the new version of the SL-AV dynamical core presented combines the accuracy and stability of the standard SL-AV dynamical core with the mass-conservation properties. The results of the mountain-induced Rossby-wave test and baroclinic instability test for the mass-conservative dynamical core are found to be in agreement with the results available in the literature.
The methods of impedance spectroscopy of (Al, In, Ga)As-based pHEMT heterostructures are developed using an LCR meter in the frequency range 0.1-2000 kHz and a vector network analyzer at higher ...frequencies of 0.01-3 GHz. These methods determine all the main parameters of the pHEMT heterostructures, including the threshold voltage, the channel resistance, the sheet density of electrons, and their mobility at operating biases.
The fabrication process of ohmic contacts to a diamond-like carbon (DLC) layer is described with the sequential deposition of a Au/Mo/Ti metallic layer onto it. The contacts have good mechanical and ...adhesion properties. Their specific contact resistance is varied from 1.4 × 10
–4
to 6.4 × 10
–5
Ω cm
2
depending on the DLC layer thickness. The temperature dependence of the layer film resistance is investigated. It is shown that thin DLC layers provide better characteristics of an ohmic contact due to their more uniform graphitization during thermal annealing.
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