Vol. 108, No. 1 * Pages 1–77 * January - March 2004

Radiative forcings of aerosol components and greenhouse gases were studied by a box model in Hungary. Direct climate forcing of aerosol was calculated by using chemical, optical, and meteorological data found in the examined region, while the forcing of greenhouse gases was determined by formulas with global constants and regional concentrations. The climatic effects of these species were compared with their forcings estimated for the beginning of eighties. The climatic effect of ammonium sulfate and carbon dioxide varied significantly during the last two decades. Positive forcing of carbon dioxide increased by 60%, while cooling effect of anthropogenic ammonium sulfate aerosol decreased by 45%. That is, both important trace components in the air helped the warming of regional climate during this period.

Relationships between meteorological variables and particles, metals and their size fraction concentrations were determined from samples collected in different climatic situations. Special attention was focused on the effect of rain. Single correlation and multiple regression statistical methods were performed on samples from both rainy and dry days. Coarse particle concentrations diminished linearly when rainfall increased. The metals Fe, V, Ni, Ti, and Mn diminished as well. A substantial concentration effect was produced by the temperature on TSP, Fe, Ti, and Mn concentrations in fine particles. Also, a dispersion effect was produced by the atmospheric pressure on TSP, Mn, Fe, Ti, Ni, and V concentrations in these particles. Besides, there was a dispersion effect by the wind speed on TSP and Cd concentrations. The fine particles and metals between 1.3 and 0.6 micrometers are those best correlated with meteorological parameters. Multiple linear regression was demonstrated to be a powerful tool to explain the particle and metal levels in relation to size distribution and meteorology.

The purpose of this research was to develop a numerical model to estimate the occurrence of thunderstorms and hailstones on the ground. This model is a part of the nowcasting system (MEANDER) developed by the Hungarian Meteorological Service. The formation of the thunderstorms was estimated by running a one-dimensional, steady state model at every grid point of the mesh covering the Carpathian Basin. Using sounding and surface data over a grid with 3 km horizontal resolution initialized the model. The outputs of the model are: vertical profile of temperature and updraft velocity of the ascending air parcel, furthermore, the size of the largest hailstone on the ground. Convective Available Potential Energy (CAPE) is also calculated to estimate convective activity. The predicted occurrence of the thunderstorms was compared to radar observations. The calculated maximum hailstone sizes were checked by using reports of the voluntary observers. The comparisons show that nowcasting system overestimates the occurrence of the thunderstorm formation; about 20% of the alarms were false. In most cases the nowcasting system forecasted the formation of the thunderstorms one hour before they appeared. 

In this paper, we discuss the computational difficulties of merging line-mixing models into line-by-line computations. We present the technical details of the upgrade of the High-resolution Atmospheric Radiative Transfer Code (HARTCODE) into an accurate reference line-by-line code for line mixing computations in the Q branches of the CO₂. The implementation of line mixing was based on the model, database, and software that were developed at the Laboratoire de Physique Moleculaire et Applications (LPMA), and the HITRAN2K database absorption line compilation. In the recent version of the line mixing database 306 vibrational bands of eight CO₂ isotopes are included, and there are provisions for calculations using the first order and the more accurate relaxation operator method. The successful integration of the line mixing computations has been validated using airborne and ground‑based high‑resolution HIS radiance measurements. This exercise can also be regarded as the validation of the line mixing database for high resolution, nadir viewing thermal emission measurements.

The analysis of the wind speed profile measurements carried out above maize canopy during the whole growing season were used for dependence parameterization of the dynamic roughness length z₀ as well as aerodynamic resistance r_a on the wind speed u(z). The investigated experimental field is situated in Žabčice, Czech Republic (49^°01¢N, 16^°37¢E, 179 m a.s.l.). The zero plane displacement d, the roughness length z₀, and the aerodynamic resistance r_a values were determined during the whole maize growing season. On the basis of these values, the dependence of the z₀ and ra values on the wind speed was found and quantitavely expressed for this canopy surface. For zero plane displacement d we accepted the fact, that the relation d = (2/3)h is well representative for agricultural crop covered surfaces. The average roughness length of closed maize canopy was from 0.24 m in August to 0.19 m in October with mean canopy height of 2.24 m and 2.15 m, respectively. The dependence of friction velocity u* on the wind speed u(0.5 m) can be fitted as  The function z₀ = f(u) can be analyzed as the dependence of the relative roughness length x₀ = z₀/h on the nondimensional speed G= u(h)/u*. For this dependence the analytical relationship was found in the form:  The aerodynamic resistance decreases with increasing wind speed. This dependence is more complicated, because the r_a-values depend also on the rougness length and atmosphere’s thermal stratification.