Zoltán Sümeghy

Temperature cross-section features in an urban area

Abstract This study examines the connection between the built-up urban surface and near-surface air temperature. The studied city (Szeged, Hungary) is located on a low and flat flood plain with a population of 160,000. Data were collected by mobile measurements under different weather conditions between March 1999 and February 2000. The efforts have been focussed on investigating the maximum development of the urban heat island (UHI) along an urban cross-section. According to the results, the UHI intensity changed according to season and month, as a consequence of the prevailing weather conditions. The role of cloudiness and wind speed on the temporal variation of the largest UHI, which represents the increasing effect of Szeged on temperature, is clearly recognized during most of the time in the studied period. The seasonal profiles follow remarkably well the general cross-section of the typical UHI described by Oke (Oke, T.R., 1987. Boundary Layer Climates. Routledge, London) who defines its characteristic parts as ‘cliff’, ‘plateau’ and ‘peak’. The usefulness of the normalized values in the investigation is proved, the form of the seasonal mean UHI profile is independent of the seasonal climatological conditions, and is determined to a high degree by urban surface factors. As a conclusion, we suggest a modified model describing the metropolitan temperature variable for cities situated in simple geographical conditions: it is equal to the sum of components of the basic climate of the region and of the production of urbanization at the surface, where this last term is a multiplication of weather and urban surface factors.

Land-use and meteorological aspects of the urban heat island

This study examines the influence of urban and meteorological factors on the surface air temperature field of the medium-sized city of Szeged, Hungary, using mobile and stationary measurements under different weather conditions between March and August 1999. This city, with a population of about 160 000, is situated on a low, flat flood plain. Efforts have been concentrated on investigating the maximum development of the urban heat island (UHI). Tasks include the determination of the spatial distribution of seasonal mean maximum UHI intensity and modelling of existing conditions in the period being studied. Multiple correlation and regression analyses are used to examine the effects of urban parameters (land-use characteristics and distance from the city centre determined in a grid network) and of meteorological parameters (wind speed, temperature) on thermal conditions in the study area. The results indicate isotherms increasing in regular concentric shapes from the suburbs towards the inner urban areas where the mean maximum UHI intensity reaches more than 3°C in the studied periods. A strong relationship exists between urban thermal excess and distance, as well as built-up ratio. In contrast, meteorological conditions do not have any significant effect on the UHI intensity at the time of its maximum development. Copyright

The effect of different transport modes on urban PM10 levels in two European cities

The aim of the study is to identify transport patterns that may have an important influence on PM10 levels in two European cities, namely Szeged in East-Central Europe and Bucharest in Eastern Europe. 4-Day, 6-hourly three-dimensional (3D) backward trajectories arriving at these locations at 1200 GMT are computed using the HYSPLIT model over a 5-year period from 2004 to 2008. A k-means clustering algorithm using the Mahalanobis metric is applied in order to develop trajectory types. Two statistical indices are used to evaluate and compare exceedances of critical daily PM10 levels corresponding to the trajectory clusters. For Bucharest, the major PM10 transport can be clearly associated with air masses arriving from Central and Southern Europe, as well as the Western Mediterranean. Occasional North African dust intrusions over Romania are also found. For Szeged, Southern Europe with North Africa, Central Europe and Eastern Europe with regions over the West Siberian Plain are the most important sources of PM10. The occasional appearance of North-African-origin dust over Hungary is also detected. A statistical procedure is developed in order to separate medium- and long-range PM10 transport for both cities. Considering the 500 m arrival height, long-range transport plays a higher role in the measured PM10 concentration both for non-rainy and rainy days for Bucharest and Szeged, respectively.

Comparison of objective air-mass types and the Péczely weather types and their ability to classify levels of air pollutants in Szeged, Hungary

This paper compares the efficiency of a system of objective air-mass types and the Peczelys 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 Peczely-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 Peczely-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 Peczely-types. In the summer months, neither the objective nor the Peczely classifications are effective in categorisation of pollutant concentrations.

Relationship between the Péczely's large‐scale weather types and airborne pollen grain concentrations for Szeged, Hungary

This paper discusses a subjectively defined system of air mass types, the 13 Péczelys 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 Péczelys 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 (1997–2001). It was found that Péczelys 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 Péczelys large‐scale weather situations cannot alone be considered as an overall system in predicting pollen concentrations.

Estimating the daily Poaceae pollen concentration in Hungary by linear regression conditioning on weather types

Abstract Objectively defined clusters of meteorological elements and weather types described by weather fronts and precipitation occurrences are produced in order to classify Poaceae pollen levels. The Poaceae pollen concentration was then estimated one day ahead for each of the above categories of days at the villages of Szeged and Győr in Hungary. The database describes an 11-year period from 1997 to 2007. For weather-front recognition purposes, the ECMWF ERA-INTERIM database was used. In order to estimate the actual daily Poaceae pollen concentrations, previous-day values of five meteorological variables and previous-day Poaceae pollen concentrations were applied. We find that both for Szeged and Győr, as well as both for the subjective and objective classifications, high daily mean Poaceae pollen levels are favoured by anticyclone ridge weather situations, as we might expect. When estimating the Poaceae pollen level, the previous-day pollen concentration, previous-day mean temperature, and previous-day mean global solar flux for Győr were statistically significant, but for Szeged it was only the previous-day pollen concentration. Taking into account the clusters, the objective classification based on original data proved the most effective. For the subjective classification, the best estimates were obtained for days with a warm front and precipitation.

Plants remember past weather: a study for atmospheric pollen concentrations of Ambrosia, Poaceae and Populus

After extreme dry (wet) summers or years, pollen production of different taxa may decrease (increase) substantially. Accordingly, studying effects of current and past meteorological conditions on current pollen concentrations for different taxa have of major importance. The purpose of this study is separating the weight of current and past weather conditions influencing current pollen productions of three taxa. Two procedures, namely multiple correlations and factor analysis with special transformation are used. The 11-year (1997–2007) data sets include daily pollen counts of Ambrosia (ragweed), Poaceae (grasses) and Populus (poplar), as well as daily values of four climate variables (temperature, relative humidity, global solar flux and precipitation). Multiple correlations of daily pollen counts with simultaneous values of daily meteorological variables do not show annual course for Ambrosia, but do show definite trends for Populus and Poaceae. Results received using the two methods revealed characteristic similarities. For all the three taxa, the continental rainfall peak and additional local showers in the growing season can strengthen the weight of the current meteorological elements. However, due to the precipitation, big amount of water can be stored in the soil contributing to the effect of the past climate elements during dry periods. Higher climate sensitivity (especially water sensitivity) of the herbaceous taxa (Ambrosia and Poaceae) can be definitely established compared to the arboreal Populus. Separation of the weight of the current and past weather conditions for different taxa involves practical importance both for health care and agricultural production.

The effects of the current and past meteorological elements influencing the current pollen concentrations for different taxa

BackgroundIt is an important issue to separate the current and past components of the meteorological parameters influencing the current pollen concentration for different taxa. For this purpose a new statistical procedure, factor analysis with special transformation is introduced. The data set used covers an 11-year period (1997–2007) including daily pollen counts of 19 taxa and 4 climate variables (mean temperature, precipitation amount, global solar flux and relative humidity).ResultThe taxa examined can be classified into three groups, namely arboreal deciduous (AD), arboreal evergreen (AE) and herbaceous (H) taxa. It was found that a better comparison can be established if the taxa are separated within each group according to the starting month of their pollen season. Within the group of AD taxa, Alnus, Populus and Ulmus are marked by a late summer – early autumn peak of the role of past meteorological elements exceeding the role of the current ones almost all over the pollen-free period. For Juglans, Morus, Platanus and Quercus, the major weights of the current meteorological elements in the spring and early summer show the most characteristic contribution to the pollen production. For AE taxa, the picture is no clear. For H taxa, the curves of Cannabis, Plantago, Rumex and Urtica indicate the most equalized course of weights. Ambrosia, Artemisia and Chenopodiaceae comprise the highest weights of the past weather conditions of all taxa until at least three months before the start of the pollination. Interactions between the phyto-physiological processes and the meteorological elements are evaluated.ConclusionSeparation of the weight of the current and past weather conditions for different taxa involves practical importance both for health care and agricultural production.