A5027465895- Meteorological Phenomena and Simulations
- Atmospheric aerosols and clouds
- Oceanographic and Atmospheric Processes
- Climate variability and models
- Seismic Imaging and Inversion Techniques
- Atmospheric and Environmental Gas Dynamics
- Atmospheric chemistry and aerosols
- Radiative Heat Transfer Studies
- Atmospheric Ozone and Climate
- Geophysics and Gravity Measurements
- Tropical and Extratropical Cyclones Research
- Underwater Acoustics Research
- Ocean Waves and Remote Sensing
- Numerical methods in inverse problems
- Calibration and Measurement Techniques
- Fluid Dynamics and Vibration Analysis
- Planetary Science and Exploration
- Methane Hydrates and Related Phenomena
- Fluid Dynamics Simulations and Interactions
- Climate Change and Health Impacts
- Solar Radiation and Photovoltaics
- Arctic and Antarctic ice dynamics
- Aeolian processes and effects
- Gas Dynamics and Kinetic Theory
- Wind and Air Flow Studies
Tallinn University of Technology
2018
University of Tartu
1998-2014
Tartu Observatory
1996-2001
Estonian Academy of Sciences
1984-1990
Climate change in recent decades has been identified as a significant threat to natural environments and human wellbeing. This is because some of the contemporary changes climate are abrupt result persistent state systems; so called regime shifts (RS). study aimed detect analyse timing strength RS Estonian at half-century scale (1966−2013). We demonstrate that extensive winter warming Northern Hemisphere late 1980s was represented atmospheric, terrestrial, freshwater marine systems an extent...
A nonhydrostatic pressure-coordinate model of atmospheric dynamics is developed. The filters acoustic mode. Internal waves are filtered using the assumption non-divergence motion in pressure-space. External (Lamb mode) surface pressure adjustment. implemented framework numerical weather prediction HIRLAM (High Resolution Limited Area Model) as an extension to hydrostatic kernel. integration scheme either explicit or semi-implicit Eulerian leapfrog time stepping. Due filtration, supports...
Two-time-level, semi-implicit, semi-Lagrangian (SISL) scheme is applied to the non-hydrostatic pressure coordinate equations, constituting a modified Miller—Pearce—White model, in hybrid-coordinate framework. Neutral background subtracted initial continuous dynamics, yielding equations for geopotential, temperature and logarithmic surface fluctuation. Implicit Lagrangian marching formulae single time-step are derived. A disclosure presented, which results an uncoupled diagnostic system,...
Estimation of accuracy different high-resolution, sound-filtered, pressure-coordinate models is carried out by modeling their response to orographic forcing. Evaluated are the elastic nonhydrostatic model (EFM), anelastic (AEM), and hydrostatic primitive equation (HSM). These compared exact, nonfiltered, nonhydrostatic, dynamics (ExM). All equations linearized, a wave for vertical displacements air particles derived, exact analytical stationary solutions each uniform flow over given smooth...
A nonhydrostatic, acoustically filtered model of atmospheric dynamics in pressure coordinates is derived using a special filtering technique. The initial complete nonhydrostatic equations space are linearized. linearized system divided into two subsystems—an independent equation for potential vorticity, which determines the quasi-solenoidal horizontal flow and local invariant absence heat sources, fourth-order wave describing acoustical buoyancy waves. Lagrangian function, corresponding to...
Abstract To solve a horizontally spectral, vertically discrete buoyancy wave equation in conditions of arbitrary wind and temperature distribution with height, novel method is applied, which consists presentation the solution form cumulative product complex decrease factors. For factors, nonlinear, inhomogeneous, two-member recurrence formula follows that initiated, assuming radiative condition at top. Singularities equation, corresponding to critical layer vicinity evanescent wind, are...
Abstract The anelastic sigma‐coordinate version of the pseudo‐anelastic Miller‐Pearce model is developed. characterized by presence external‐mode acoustic perturbations which propagate in horizontal, compromising performance need to use smaller time steps than would otherwise be required. approach developed this study allows for filtering waves and adjustment surface pressure perturbations. tested a new numerical implementation an adiabatic non‐hydrostatic results are found comparable...
The semi-implicit semi-Lagrangian (SISL), two-time-level, non-hydrostatic numerical scheme, based on the nonhydrostatic, semi-elastic pressure-coordinate equations, is tested in model experiments with flow over given orography (elliptical hill, mountain ridge, system of successive ridges) a rectangular domain emphasis accuracy and effect presentation capability. Comparison demonstrates good (in strong primary wave generation) to satisfactory weak secondary reproduction some cases)...
The anelastic sigma-coordinate version of the pseudo-anelastic Miller-Pearce model is developed. characterized by presence external-mode acoustic perturbations which propagate in horizontal, compromising performance need to use smaller time steps than would otherwise be required. approach developed this study allows for filtering waves and adjustment surface pressure perturbations. tested a new numerical implementation an adiabatic non-hydrostatic results are found comparable unadjusted...
Abstract Orographic drag formation is investigated using a numerical wave model (NWM), based on the pressure-coordinate dynamics of non-hydrostatic HIRLAM. The surface drag, stress (vertical flux horizontal momentum), and are split to longitudinal transverse components presented as Fourier sums their spectral amplitudes weighted with power spectrum relative orographic height. NWM accomplished, enabling investigation buoyancy stress, generation by orography then applied cold front,...
Starting from the hydrostatic primitive equations in pressure coordinates, a quasigeostrophic (QG) model is derived with temperature and ground surface (GSP) as governing prognostic fields. In this two different tendency for GSP exist: one expressing mass conservation, other condition of zero vertical velocity at common physical space. Comparison them loads to diagnostic relationship that provides boundary omega equation. Equivalence system QG employs potential vorticity equation...
Nonhydrostatic acoustically filtered equations of motion nonviscid fluid are derived in pressure coordinates.A complete set nonhydrostatic nonlinear for ideal coordinates serves as the starting basis.These linearized and transformed to a convenient filtering form.Acoustic is achieved limit infinitely high sound speed, ¢, -00.The model lacks acoustic wave solutions but maintains without loss accuracy all slow processes, including buoyancy waves.The obtained this way linear complemented by...