The evolution of a large-scale azimuthal velocity field in a rotating cylindrical layer of fluid (radius 150 mm, depth 30 mm, free upper surface) with meridional convective circulation was studied experimentally. Two cases were considered: inward upper level circulation provided by a rim heater at the periphery and outward upper level circulation provided by a central heater. The heating rate is characterized by the Grashoff number defined through the heat flux. The detailed 3D structure of the mean large-scale velocity field is reconstructed using the PIV technique for large interval of Grashoff number values. It was shown that the energy of meridional circulation grows with the Grashoff number in the same way for both directions of circulation. Due to the action of the Coriolis force the meridional flow results in differential rotation. Meridional circulation leads to substantial variation of the integral angular momentum. Inward circulation results in the growth of the integral angular momentum and outward circulation causes it to decrease. At the same heating power, the increase of angular momentum at inward circulation is much stronger than its decrease at outward circulation.
The state-dependent error of the MM5 model for the geopotential, temperature and relative humidity fields in different synoptical patterns during a winter season over the Atlantic Ocean is considered. The evolution of the model error throughout the integration period is shown. Parts of synoptical patterns responsible for the largest model error are outlined.
An analytical theory of the moist convective instability of the rotating thermally stratified viscous and heat-conducting atmospheric layer is created [12,13,16,17]. A conventional parameterization scheme of the heat source caused by the condensation latent heat release, similar CISC parameterization, is used. The theory may be taken as a generalization of the classical theory of the Rayleigh convective instability for a case of the water vapor phase transfers. The theory demonstrates the fundamental difference between the moist convective instability and the Rayleigh instability: it is shown, that the instability region on the plane of the problem parameters c nsists of tw subregions, in the first one loc lized over the space “hurricane like” structures have o o a the largest growth rate, and only in the second one – periodic over the space structures. The theory developed describes a number of peculiarities in the dynamics of clouds, cloud streets and tropical cyclones. It destroys a conventional opinion, that CISC and similar parameterizations can not lead to the development of the localized structures of the tropical cyclones size.
A test of efficiency of the one-dimensional non-stationary baroclinic non-adiabatic model with “b-l”-closure works, using the special observational archive of FGEW (December 1978 – November 1979), was carried out. Reliability of the received results was verified qualitatively and quantitatively: comparing visually the space–time sections and the seasonal behaviour of the fact and calculated meteorological magnitudes and with the statistical methods (the correlation and difference coefficients) accordingly. Such comparing analysis has showed the good agreement between calculated and observed air temperature, wind speed and direction fields sufficiently.
In the paper the general atmospheric circulation model sensitivity to the surface characteristics changes in the urban areas is analyzed. It was shown that surface temperature in the certain areas got closer to the climatic values in the experiments taking into account city surface features. Later on we will change the city parameters in other ways for the areas where no improvement was obtained.
The three-dimension diagnostic and prognostic models of frontal cloud systems have been used for investigation of atmospheric phenomena connected with atmospheric fronts and their cloud systems that caused the damage events. Case of high convective cell caused aircrafts accident (August of 2006) will be presented in detail. It is found that is plausible to assume that crash was caused by conditions as follow: violent development of chimney clouds on the way of aircraft; cells of the strong vertical motions that can make the flight out of control; zones of instability that caused strong turbulence; chimney convective clouds with crystal tops and mixed layers that caused riming of aircraft.
3-D forecasting microphysical models of frontal cloud systems were adapted to extreme conditions during the tornado activity. Models with and without including of a complex relief developed in UHRI have been used for theoretical interpretation of the investigated phenomena. Conditions of formation and evolution of the deep convective cells, strong updrafts and downdrafts, strong rotation during passing of tornados over the north part of the Crimea on July 22, 2002 were investigated in this paper. Series of numerical experiments have been carried out with aim to research the key parameters caused features of development of dangerous events and their activity.
Within a framework of the hydromechanical model (HMM) of a tropical cyclone (TC) motion, the
“queasyprognostic” calculations of TC’s movement are carried out during the 2001 and 2003 year seasons. A
TC motion is defined by a large scale wind field and TC intensity. “Queasyprognostic” means, that an objective
analyses of a large scale wind field and an objective analyses of a TC intensity are used during an all life cycle
of a TC. The model contains parameters describing a size of a TC and a distribution of a tangential wind of a
TC. It is shown, that an appropriate choice for everyone TC of meanings of these parameters (constants) during
a “beforeprognostic” period, provides enough good agreement between an actual and calculated tracks of
various types for a “queasyprognostic” period up to 9 days. A duration of a “beforeprognostic” period in the
case of a real prognostic calculations corresponds to a period, for which information about a privies TC motion
is available. Thus, model parameters may be enough correctly defined during a “beforeprognostic” period. The
HMM may be taken as a base for a development of the new track prediction model.
This paper presents a new turbulence closure model based on the budget equations for the key second
moments: turbulent kinetic and potential energies: TKE and TPE (comprising the turbulent total energy:
TTE = TKE + TPE) and vertical turbulent fluxes of momentum and buoyancy (proportional to potential
temperature). Besides the concept of TTE, we essentially use the non-gradient correction to the traditional
buoyancy flux formulation (disregarded in the traditional formulations for the eddy conductivity). In the
proposed model, turbulent motions exist at any values of the gradient Richardson number, Ri. Instead of its
critical value separating – as usually assumed – the turbulent and the laminar regimes, the model, as well as
experimental data, reveals a transition interval, 0.1<Ri<1, which separates two regimes of principally
different nature but both turbulent: strong turbulence at Ri«1; and weak turbulence, capable of transporting
momentum but much less efficient in transporting heat, at Ri>1. Predictions from the model are consistent with
available data from atmospheric and laboratory experiments, direct numerical simulation (DNS) and large-eddy
simulation (LES).
The results of several numerical mesoscale verification experiments of computer system NOSTRADAMUS for radionuclide atmospheric dispersion and WRF model are presented on the base of comparison .with dataset.
During the last decade a new field of atmospheric modelling – the chemical weather forecasting (CWF) – is quickly developing and growing. However, in the most of the current studies and publications this field is considered in a simplified concept of the off-line running chemical transport models with operational NWP data as a driver. A new concept and methodology considering the chemical weather as two-way interacted meteorological weather and chemical composition of the atmosphere is suggested and discussed. The on-line integration of mesometeorological models and atmospheric aerosol and chemical transport models gives a possibility to utilize all meteorological 3D fields in the chemical transport model at each time step and to consider feedbacks of air pollution (e.g. urban aerosols) on meteorological processes/climate forcing and further on the chemical composition. This very promising way for future atmospheric simulation systems (as a part of and a step to Earth System Modelling) will lead to a new generation of models for meteorological, environmental and chemical weather forecasting. The methodology how to realise the suggested integrated CWF concept is demonstrated on example of the European Enviro–HIRLAM integrated system. Importance of different feedback mechanisms for CWF is also discussed in the paper.
The influence of the Tomsk city on the chemical and disperse composition of surface atmospheric aerosols has been estimated by means of carrying out several continuous measurement campaigns at two different sites (urban and rural). It is shown that the determining factors in formation of aerosol field over a moderate city are the prehistory of air masses and the activity of erosion processes in summer.
A study of air qualities has been done in 11 Siberian cities from Irkutsk (easternmost) to Novosibirsk (westernmost) in winter and summer with a mobile measurement station. It is shown that in winter a modern industrial city is not only a “heat island”, but also a “pollution island”. Admixtures concentration in centers of most cities is much higher than in their periphery. The exception is ozone, which is apparently destroyed by industrial emissions in the center and replenished in the periphery. In summer the local circulation is considerably weakened, and the difference between the parameter values for the center and periphery not always remains.
The paper presents the results of long-range atmospheric model developed specifically for the Southern hemisphere conditions. The model utilizes a combined Eulerian-Lagrangian description of the transport and diffusion of pollutants, calculation of their chemical transformations, dry and wet deposition as well as the pH value of precipitation.
Adaptation of an open numerical weather model ММ5 to geographical conditions of Ukraine is executed and the preliminary estimation of success forecasting of spatial pressure and temperature fields is analyzed for Ukraine territory and areas of nuclear power plants. Interaction of model ММ5 and diffusion model “LEDI” provides necessary operational efficiency in an estimation of distribution of radioactive emissions from the nuclear power plant.
Recent research suggests that the evolution of the stable ABL is still poorly understood. Certain advances in theory and modeling of the stable ABL (SABL) are assessed. Inclined strongly SABL is addressed. We show that a relatively thin and strongly SABL, as recently modeled using an improved “z-less” mixing length, can be successfully treated; the result is quietly extended to other types of SABL. Finally, a generalized “z-less” mixing length is proposed.
A method based on the evolution of the height of the convective boundary layer that has been successfully used for aggregation of sensible heat and momentum fluxes is here applied for aggregation of CO 2 fluxes over Zealand in Denmark. Inputs for the method are vertical profile measurements of CO 2 concentrations, standard measurements of the CO 2 concentration near the ground and successive radio-soundings. The aggregated fluxes of CO 2 represent a combination of agricultural and forest surface conditions.
The extraction and processing of minerals from surface mines and quarries can produce significant fugitive emissions as a result of site activities such as blasting, unpaved road haulage, loading, primary crushing and stockpiling. Uncontrolled fugitive dust emissions can present serious environmental, health, safety and operational issues impacting both site personnel and the wider community. Simulation technology is finding increasing use for the purposes of advanced warning of potential problem emissions in addition to providing a basis for future planning applications where demonstrable compliance with regulatory requirements are necessary. The initial re-entrainment and subsequent dispersion of fugitive dust presents a process complicated by the combination of the in pit topography, the surrounding natural topography and the dynamic nature of emissions from these sites. These factors impact upon the accuracy and reliability of the conventional Gaussian plume based computational prediction methods employed for regulatory compliance and IPPC applications. This paper proposes that optimal modelling of open pit emissions may be more accurately achieved by the use of a multi-scale predictive modelling approach utilising computational fluid dynamic (CFD) methods for high resolution near source dispersion and conventional Gaussian based methods for far field dispersion modelling.
This paper presents a numerical based flow and dispersion analysis of a typical UK based open pit utilising CFD in conjunction with a conventional Gaussian plume based methods. Typical operating emissions and meteorological conditions are obtained from long term data records collected at a large operating quarry extraction operation in the UK. Emissions are modelled using a Lagrangian framework within conventional atmospheric boundary layer (ABL) profiles expressed as functions of turbulence and velocity parameters under assumed neutral conditions. Results are presented in terms of the impact of site topography on in pit retention as compared to the Gaussian based method.
The spatial and temporal variability of the meteorological (for temperature and wind), concentration and deposition fields resulted from hypothetical accidental releases occurred in the metropolitan area is evaluated on an example of the urban area of Copenhagen, Denmark. Dependence of these fields on the temporal variability of meteorological variables in the lower surface layer was estimated as a function of modified parameters.
A numerical simulation of flows in urban canopy is important from the view point of emergency preparedness and development of new schemes for parameterization of atmospheric boundary layer in NWP. This study performs the analysis of spatial averaged properties of flow around different urban like obstacles.
We have applied the MM5-CMAQ model to simulate the high concentrations in PM10 and PM2.5 during a winter episode (2003) in Central Europe. The selected period is January, 15 -April, 6, 2003. Values of daily mean concentrations up to 75 gm -3 are found on average of several monitoring stations in Northern Germany. This model evaluation shows that there is an increasing underestimation of primary and secondary species with increasing observed PM10. The high PM levels were observed under stagnant weather conditions, that are difficult to simulate. The MM5 is the PSU/NCAR non-hydrostatic meteorological model and CMAQ is the chemical dispersion model developed by EPA (US) used in this simulation with CBM-V. The TNO emission inventory was used to simulate the PM10 and PM2.5 concentrations with the MM5-CMAQ model. The results show a substantial underestimation of the elevated values in February and March, 2003. An increase on the PM2.5 emissions (five times) produces the expected results and the correlation coefficient increases slightly. The WRF/CHEM model results show an excellent performance with correct emission database. The main difference between MM5-CMAQ simulations and WRF/CHEM is the MOSAIC particle models and the “classical” MADE/SORGAM particle model used in WRF/CHEM and CMAQ respectively. MOSAIC seems to make a better job than MADE particle model for this particular episode.
The model estimation and analysis of existent hypothetical variants of extreme accidents in utilizing atomic submarines with radioactivity leakage to the atmosphere or see surface have been performed. The consequence of air pollutions for such accidents, by estimate, can found at the distance not far from the source. Unlike situation with pollution transport by atmospheric way, significant radionuclide concentrations after falling into the water surface may become a problem for areas of water at long distances from the place of accident.
Solution of the 3D turbulent diffusion equation, based on the alternating direction method, is proposed. The advantage of this scheme is its physical validity and high stability. The numerical algorithm, developed, allows including the computing unit of air pollution dispersion in the 3D unsteady boundary layer of the atmosphere.
The new decision of equation of turbulent diffusion, which takes into account co-operation of coefficients of turbulent diffusion and speed of wind in the direction of axes of the system of co-ordinates, is got. The formulas of calculations allow to get the fields of concentrations at any states of thermodynamic of atmosphere and speeds of wind, including at a calm without approximations of scales of diffusion from distance.