We study the scaling laws and structure functions of stratified shear flows by performing high-resolution numerical simulations of inviscid compressible turbulence induced by Kelvin-Helmholtz instability. Hide

We use numerical simulation to examine the important role by the background shear currents on the “short-lived” nature of mode-2 ISWs observed previously. Our results also confirm the hypothesis of Shroyer et al. (2010). It was shown that the Mode-2 internal solitary waves under the shear currents will adjust through the generation of multiple wave forms, of which the amplitude-modulated wave packet is important for the energy transfer during early modulation process. Hide

We consider the well known in geophysics nonlinear model for deep water surface gravity waves – the envelope Zakharov equation. This model predicts that waves can propagate as a stable localized groups – breathers. We study numerically in details the breather collision process and found several fundamentally different effects when compared to the previously known results. In particular we show the formation of extreme amplitude waves, that may cause serious damage when appear in seas and oceans. Hide

We investigate the modelling of the effects of the unresolved scales on the large scales of the coupled ocean-atmosphere model MAOOAM. Two different physically-based stochastic methods are considered and compared, in various configurations of the model. Both methods show remarkable performances and are able to model fundamental changes in the model dynamics. Ways to improve the parameterizations implementation are also proposed. Hide

This paper presents a comparison of two processes that start the generation of energy from the Earth. It does this by using a sequence of equations to provide the level of either process by using previously determined from geophysical measurements far from active volcanic sites and a few hundred years after the activity. This work is necessary in order for us and other geophysicists to examine the various nuclei present in this energy generating process after the reactions are completed. Hide

· Laboratory and numerical experiments are conducted to investigate stem waves due to incidence of monochromatic waves. · For larger amplitude waves with smaller angle of incidence, the measured data show clearly stem waves. · Increase of wave length due to nonlinearity is responsible for the development of stem waves. · Existence and properties of stem waves found theoretically are fully supported by the physical experiments. Hide

The experimental results show that the seepage network of sandstone is similar to the BA scale-free network in the structural characteristics. The average path length of sandstone generally increases with the increase of network magnitude. The average of number of edges of node plays a dominant role for the porosity of sandstone. At the same time, sandstone seepage network has better fault tolerance rate and robustness to external random attacks. Hide

This study presents, to our knowledge, the first data assimilation experiments in the Marmara Sea. We proposed a ferrybox network for monitoring the state of Marmara Sea and showed that assimilation of the temperature and salinity improves the forecasts in the basin. The flow of the Bosphorus helps to propagate the error reduction. The study can be taken as a step towards a marine forecasting system in the Marmara Sea which will help to improve the forecasts in the adjacent Black and Aegean Seas. Hide

Accurate estimation of subsurface geological parameters, e.g. permeability, is essential for the oil industry. This is done by combining observations of pressure with a mathematical model using data assimilation. We show that computationally affordable ensemble transform data assimilation methods are suitable for the parameter estimation. Particle filter is superior to Kalman filter for estimation of a small number of parameters and is equivalent for estimation of a large number of parameters. Hide

Strong internal waves have a significant influence on underwater marine environment and off-shore engineering facilities. They induce noticeable currents and take part in the processes of mixing of water layers, suspending and transport of sediment particles and formation of sea bottom relief. We consider probability of emergence of large-amplitude internal waves on a base of instrumental measurements of internal wave field in five different regions of the world ocean. Hide

While the butterfly effect renders the forecasting problem in chaotic physical applications inherently volatile, chaotic dynamics also put strong constraints on the evolution of prediction errors. Using the framework of chaotic dynamical systems, we analyze the asymptotic properties of ensemble based Kalman filters, and how these are influenced by the dynamical constraints in the model, especially in the context of random model errors and small ensemble sizes. Hide

Ensemble Variational Assimilation (EnsVAR) has been implemented on two small dimension non-linear chaotic toy models, as well as on linearized version of those models. In the linear case, EnsVAR is exacly Bayesian and produced highly reliable ensembles. In the nonlinear case, EnsVAR, implemented on temporal windows on the order of magnitude of the predictability time of the systems, shows as good performance as in the exactly linear case. EnsVar is a good as an estimator as EnKF and PF. Hide