Investigation of dust storms in Ilam and the performance analysis of simulation of 6 numerical prediction models at a severe dust storm in west of Iran

Introduction: Many countries encounter dust storms phenomenon that is one of the meteorological problems leading to many disturbances. Materials and methods: Although the dust storm is historically recorded as an old event in some provinces of Iran, but it becomes a new event in some parts such as Ilam province. Results: After statistical investigation of dust storms in Ilam province, the dust storm from 3td to 6th July 2016 are studied. The source of this dust storm was the eastern areas of Syria and central Iraq base on the satellite images, the outputs of HYSPLIT and WRF-Chem models. Conclusion: Model outputs in intensity of surface dust concentration of MACC-ECMWF, NASA-GEOS, NCEP-NGAC, NMMB-BSC, and BSCDREAM8b models are compared to the observation data in Ilam city and results show that NASA-GEOS model has better performance. In display of dust dispersion on Iran, the middle of all models is more compatible with reality.

Hypothesis Testing for Autocorrelated Short Climate Time Series

Commonly used statistical tests of hypothesis, also termed inferential tests, that are available to meteorologists and climatologists all require independent data in the time series to which they are applied. However, most of the time series that are usually handled are actually serially dependent. A common approach to handle such a serial dependence is to replace in those statistical tests the actual number of data by an estimated effective number of independent data that is computed from a classical and widely used formula that relies on the autocorrelation function. Despite being perfectly demonstrable under some hypotheses, this formula provides unreliable results on practical cases, for two different reasons. First, the formula has to be applied using the estimated autocorrelation function, which bears a large uncertainty because of the usual shortness of the available time series. After the impact of this uncertainty is illustrated, some recommendations of preliminary treatment of the time series prior to any application of this formula are made. Second, the derivation of this formula is done under the hypothesis of identically distributed data, which is often not valid in real climate or meteorological problems. It is shown how this issue is due to real physical processes that induce temporal coherence, and an illustration is given of how not respecting the hypotheses affects the results provided by the formula.

DETECTION OF BROWNIAN PARTICLES (EULERIAN AND LAGRANGIAN STATISTICS OF IMPURITY PARTICLE IN ATMOSPHERE)

We study passive admixture spreading in the atmosphere considering regular (with the wind) and stochastic motion of the particles. The probability distribution of velocities on a boundary of a given spatial region (detector) is found for particles of a passive admixture. The connection between this probability distribution and the solution of the classical problem on the probability distribution of the coordinates and velocity of a Brownian particle at a fixed moment is determined. The dependence of the obtained probability density on the relation among the parameters of the problem under consideration is discussed. Some specific examples are presented. Potential applications of the results are in ecological and meteorological problems.

Numerical integration of the axisymmetric Robinson-Trautman equation by a spectral method

We have adapted the Spectral Transform Method, a technique commonly used in non-linear meteorological problems, to the numerical integration of the Robinson-Trautman equation. This approach eliminates difficulties due to the S2 × R+ topology of the equation. The method is highly accurate for smooth data and is numerically robust. Under spectral decomposition the long-time equilibrium state takes a particularly simple form: all nonlinear (l ≥ 2) modes tend to zero. We discuss the interaction and eventual decay of these higher order modes, as well as the evolution of the Bondi mass and other derived quantities. A qualitative comparison between the Spectral Transform Method and two finite difference schemes is given.

Surface Chemistry in Modern Nanotechnologies

A review of the properties of fine oxide surfaces at the nano level is given based on the author's work. It includes a scheme related to the structure of pyrogenic silica and the changes induced by dehydroxylation as studied by quantum chemical and spectroscopic methods. The application of non-linear optical methods has appeared to be useful for the investigation of disperse solid structures. Quantitative measurements of intermolecular interaction have been obtained by light scattering. Alteration of the surface activity due to gas-phase electron–donor molecule action on chemisorbed complexes or functional groups on the surface is considered. It is also shown how the physicochemical properties of a solid surface can be changed as a result of chemical modification. The investigations discussed could lead in practice to the creation of new lightweight ceramic materials, adsorbents, catalyst supports, hollow-body microspherical fillers and medicinal preparations. Some of these are useful for nano electronics and instrument design as well as for the solution of some meteorological problems.