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About 30% of the Hungarian population has some type of allergy, 65% of them have pollen sensitivity, and at least 60% of this pollen sensitivity is caused by ragweed. The short (or common) ragweed (Ambrosia artemisiifolia = Ambrosia elatior) has the most aggressive pollen of all. Clinical investigations prove that its allergenic pollen is the main reason for the most massive, most serious and most long-lasting pollinosis. The air in the Carpathian Basin is the most polluted with ragweed pollen in Europe. The aim of the study is to analyse how ragweed pollen concentration is influenced by meteorological elements in a medium-sized city, Szeged, Southern Hungary. The data basis consists of daily ragweed pollen counts and averages of 11 meteorological parameters for the 5-year daily data set, between 1997 and 2001. The study considers some of the ragweed pollen characteristics for Szeged. Application of the Makra test indicates the same period for the highest pollen concentration as that established by the main pollination period. After performing factor analysis for the daily ragweed pollen counts and the 11 meteorological variables examined, four factors were retained that explain 84.4% of the total variance of the original 12 variables. Assessment of the daily pollen number was performed by multiple regression analysis and results based on deseasonalised and original data were compared.

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This paper discusses a subjectively defined system of air mass types, the 13 Péczely's large-scale weather situations over the Carpathian Basin in relation to the detected airborne pollen grain concentrations. Based on the ECMWF (European Centre for Medium-Range Weather Forecasts) sea-level pressure data set, daily sea-level pressure fields analyzed at 00:00 UTC were prepared for each Péczely's weather types in order to relate the sea-level pressure patterns with the average pollen levels in Szeged. The data basis for this study comprises daily values of 12 meteorological parameters and daily average pollen concentrations for 24 species in a 5-year period (1997)(1998)(1999)(2000)(2001). It was found that Péczely's anticyclonic ridge types 2 and 11 as well as cyclonic types 4 and 7 are favourable for pollen production and dispersal unlike the cyclonic types 3 and 13. Hence, the Péczely's large-scale weather situations cannot alone be considered as an overall system in predicting pollen concentrations.

This paper discusses the characteristic air mass types over the Carpathian Basin in relation to plant pollen levels over annual pollination periods. Based on the European Centre for Medium-Range Weather Forecasts dataset, daily sea-level pressure fields analysed at 00 UTC were prepared for each air mass type (cluster) in order to relate sea-level pressure patterns to pollen levels in Szeged, Hungary. The database comprises daily values of 12 meteorological parameters and daily pollen concentrations of 24 species for their pollination periods from 1997 to 2001. Characteristic air mass types were objectively defined via factor analysis and cluster analysis. According to the results, nine air mass types (clusters) were detected for pollination periods of the year corresponding to pollen levels that appear with higher concentration when irradiance is moderate while wind speed is moderate or high. This is the case when an anticyclone prevails in the region west of the Carpathian Basin and when Hungary is under the influence of zonal currents (wind speed is high). The sea level pressure systems associated with low pollen concentrations are mostly similar to those connected to higher pollen concentrations, and arise when wind speed is low or moderate. Low pollen levels occur when an anticyclone prevails in the region west of the Carpathian Basin, as well as when an anticyclone covers the region with Hungary at its centre. Hence, anticyclonic or anticyclonic ridge weather situations seem to be relevant in classifying pollen levels.

This paper compares the efficiency of a system of objective air-mass types and the Péczely's weather types in classifying pollution levels over the Carpathian Basin for the winter and summer months. Based on the ECMWF data set, daily sea-level pressure fields analysed at 00 UTC were related to the levels of air pollutants for both the objective air-mass types and the Péczely-types in Szeged. The data base comprises daily values of 12 meteorological and eight pollutant parameters for the period 1997-2001. Mean sea-level pressure fields of the Péczely-types show higher independence from each other than those of the objective clusters in both seasons. In the winter months, anticyclonic types are mostly favourable, while cyclonic ones are mostly negligible in classification of pollutant levels both for the objective and the Péczely-types. In the summer months, neither the objective nor the Péczely classifications are effective in categorisation of pollutant concentrations. 82L. Makra et al.