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IDŐJÁRÁS - angol nyelvű folyóirat

Vol. 115, No. 3 * Pages 123–218 * July - September 2011

Quarterly journal of the Hungarian Meteorological Service

letöltés [pdf: 11213 KB]
Atmospheric chemistry – Bridging the chemical air composition with the climate
Detlev Möller
idojaras.2011.3.1 (p. 123–)
 PDF (419 KB)   |   Abstract

Studying the environment is an extremely complex issue, comprising all natural sciences and regarding the “key” compartments water, air, and soil, often defined as the climate system. Without any doubt, the atmosphere is the most important one, it is highly dynamic and globally interlinking the biosphere. Nowadays, the humans are shortly before reaching the “tipping point” between moving into the (climate) catastrophe or the sustainable development. This paper introduces a new discipline, the “chemistry of the climate system”. Atmospheric chemistry, without using this term before the 1950s, was a fundamental approach in the beginning of modern chemistry (air analysis and understanding combustion) some 200 years ago, and it is now enlarging to the interfaces (“interfacial chemistry”) with the biosphere and hence our climate system. Humans created a new dimension (the “anthroposphere”) by globally modified biogeochemical cycles. Climate control means learning from nature and creating closed man-made material cycles, first of all that of carbon. Our environmental problem is not the limited energy but creating unbalanced reservoir distributions of substances with different characteristic timescales out of steady-state conditions.

Numerical simulation of the cycle of aerosol particles in stratocumulus clouds with a two-dimensional kinematic model
Beáta Szabó -Takács
idojaras.2011.3.2 (p. 147–)
 PDF (695 KB)   |   Abstract

The purpose of the paper was to develop a numerical model to study the cycle of aerosol particles in stratocumulus clouds in different air mass types. A detailed microphysical scheme was incorporated into an idealized two-dimensional kinematic model to investigate the role of the aerosol particles in the formation of the water droplets, regeneration of the aerosol particles due to evaporation of the water drops, and the washout of the aerosol particles. The calculations were made with different cloud condensation nuclei (CCN) size distributions and concentrations typical for maritime, rural, and remote continental air mass types, furthermore, with two different updraft profiles. The water droplets were formed on soluble ammonium-sulfate aerosol particles. The ratio of the number concentration of the soluble and insoluble aerosol particles depended on their size. The drops grew by condensation and collision coalescence in the updraft core, but they evaporated due to the subsaturation in the downdraft region.

The model clearly simulated the regeneration of the aerosol particles. The majority of the water soluble particles were scavenged due to the water drop formation. The efficiency of the scavenging of the water insoluble particles depended on the concentration of the water soluble aerosol particles. While Brownian effect played an important role in capturing these particles, only few of them were washed out due to the phoretic- and gravitational forces. Results of the numerical simulation show that in the case of the stratocumulus clouds the number concentration of insoluble aerosol particles larger than 0.1 µm is hardly modified due to different scavenging mechanisms.

Determination of winter barley yield by the aim of multiplicative successive approximation
Erzsébet Enzsölné Gerencsér, Zsuzsanna Lantos, Zoltán Varga-Haszonits, and Zoltán Varga
idojaras.2011.3.3 (p. 167–)
 PDF (271 KB)   |   Abstract

The aim of our study was to analyze the climate-winter barley yield relationship by means of a model which took impact of successive periods into account. This approximation is a step from statistical models to dynamic models.

Study was based on data of an agroclimatological database, which contained daily values of meteorological elements during 1951–2000 measured by the Hungarian Meteorological Service and yearly county average values of winter barley yield published by Hungarian Central Statistical Office. In order to investigate the impact of meteorological factors on yield, we separated the influence of weather and technology. Impact of meteorological factors on yield was examined by regression equations during selected periods, but only time periods with significant influence on yield were taken into consideration. Applying this model, trend function was determined firstly, then relationship between trend ratio and meteorological element of first significant time period was calculated. This process was continued until the last function of meteorological impact had been determined.

Verification and validation of results were accomplished by studying of correlation between measured and calculated values and determination of frequency distribution of estimation errors.

The multiplicative successive model is suitable for estimating yields of winter barley, which grows in the cool and wet part of the year. It demonstrates how successive periods of growing season influence yield. This method is a better tool for studying the effects of climatic variability or a possible climate change than a simple statistical model.

Air quality around motorway tunnels in complex terrain – computational fluid dynamics modeling and comparison to wind tunnel data
Márton Balczó, Miklós Balogh, István Goricsán, Torsten Nagel, Jenő M. Suda, and Tamás Lajos
idojaras.2011.3.4 (p. 179–)
 PDF (747 KB)   |   Abstract

The current paper describes numerical simulations of flow and dispersion performed in a complex suburban area of Budapest using the microscale model MISKAM and accompanying wind tunnel tests which provided reference concentration data for validation of the model results. Main pollutant sources are traffic related and include a planned motorway section of 9 km length consisting of sections running in tunnel, on ground, and on viaduct. Four different route alternatives were investigated. In the paper, first a condensed review is given about problems related to air quality around motorway tunnels in complex terrain. The effect of larger scales on microscale air quality was determined using background concentrations from monitoring station time series with removal of short-term fluctuations, for which a simple method is introduced here. The validation wind tunnel tests were carried out at several wind directions on a 1:1000 scale model containing topography, buildings, and vegetation with measurement of tracer concentrations in 50 sampling locations. In the microscale CFD simulation, flow and dispersion considering topography, vegetation, and buildings were calculated three-dimensional in a large domain using k–e  model, and advective diffusion equation was set up on a Cartesian grid treating air pollutants as non-reactive scalars. Results give more detailed information about the flow, for example local speedup above hills, slowdown in vegetation zones, separation regions are resolved well. Deviation of pollutant plume paths from the mean wind direction caused by the topography could be also observed. NOx concentration maps showed that air quality limit exceedances occur near motorway tunnel portals in form of large surface plumes, which can only be avoided by the application of tunnel ventilation stacks. These will exhaust polluted tunnel air in larger heights. The comparison of numerical results to the wind tunnel reference data was performed using statistic metrics (fractional bias, normal mean square error, geometric mean bias, geometric variance, correlation coefficient) showing a generally good agreement.

Application of a new aridity index in Hungarian forestry practice
Ernő Führer, László Horváth, Anikó Jagodics, Attila Machon, and Ildikó Szabados
idojaras.2011.3.5 (p. 205–)
 PDF (512 KB)   |   Abstract

The ecophysiological observations and the investigations of the weather dependent vital processes of the forests have clearly proved that the water supply in the main growing–main water consumption period (from May to July) as well as in the critical months (July and August) have crucial influence on the growth, vitality, and organic matter production of the forest. Evapotranspiration rate is higher in these periods; and forest ecosystems are most sensitive to the extreme weather conditions this time. Relationship between meteorological parameters and girth-growth of trees (proportional with organic matter production) can be characterized by a simplified forestry aridity index (FAI) for Hungarian conditions: FAI = 100 TVII−VIII / (PV−VII + PVII−VIII), where TVII−VIIIis the average temperature in July and August (˚C), PV–VIIis the precipitation sum (mm) of the period from May to July, and PVII–VIIIis the precipitation sum (mm) of July and August. By this index, the average weather conditions of different climate categories applied in forestry practice can be described. FAI values representative for different species are beech: < 4.75; hornbeam–oak: 4.75 − 6.00; sessile oak and Turkey oak: 6.00 −7.25; forest-steppe: >7.25.

Book review
László Bozó

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