Department of Meteorology

Urban heat island (UHI) effects on the ten most populated cities of Hungary, including the Budapest agglomeration area, were analyzed using remotely sensed data. Day-and night-time surface temperature time series observed by sensor MODIS on satellite Terra were used to determine UHI intensities. UHI intensity was defined as the difference in spatially averaged surface temperatures between urban and surrounding rural pixels. Spatial structures of UHIs were determined and compared for different seasons and macrocirculation conditions.

Fuzzy rule-based modeling is applied to the prediction of regional droughts (characterized by the modified Palmer index, PMDI) using two forcing inputs, El Nino/Southern Oscillation (ENSO) and large scale atmospheric circulation patterns (CPs) in a typical Great Plains state, Nebraska. Although, there is significant relationship between simultaneous monthly CP, lagged Southern Oscillation Index (SOI) and PMDI in Nebraska, the weakness of the correlations, the dependence between CP and SOI and the relatively short data set limit the applicability of statistical modeling for prediction. Due to the above difficulties, a fuzzy rule-based approach is presented to predict PMDI from monthly frequencies of daily CP types and lagged prior SOIs. The fuzzy rules are defined and calibrated using a subset called the learning set of the observed time series of premises and PMDI response. Then, another subset, the validation set is used to check how the application of fuzzy rules reproduces the observed PMDI. In all its eight climate divisions and Nebraska itself, the fuzzy rule-based technique using the joint forcing of CP and SOI, is able to learn the high variability and persistence of PMDI and results in almost perfect reproduction of the empirical frequency distributions. ᭧

A new statistical test (Makra-test), applicable for long time series, is introduced to identify extended sub-periods, namely, ''breaks'', average of which is significantly higher or lower than the mean of the entire time series. In order to apply this test, normal distribution of the time series being examined is a sufficient condition. In another case, if the number of elements increases in the time series, its distribution is near normal and the test can be applied, as well (according to the Central Limit Theorem). The method is demonstrated on monthly Palmer drought severity index (PDSI) data sets, computed for five stations of East Hungary in 1901-1999. Due to strongly recursive (auto-correlative) nature of PDSI every second month of the warm season (April, June, August and October) is analysed and treated as independent samples. Normality of the time series, which is a sufficient condition of the Makratest, is validated by Kolmogorov-Smirnov test and v 2 -test. Analysis of the PDSI time series indicates that separate treatment of the months is important not only to ensure the normality, but also to consider the existing slight seasonal differences in standard deviation and skewness of the index in the East-Hungarian region. The Makra-test delimits one or more (maximum 4) significant subperiods of the PDSI in every station and month (not considering the sub-intervals within the significant breaks, although most of them are also significant). Since the PDSI is based on monthly temperature and precipitation data that exhibit considerable inhomogeneities (Szentimry, 1999), the test is applied both for the original and the homogeneous time series. Effect of the inhomogeneity on long term variations of PDSI is strong: about the half of the significant breaks in the original time series disappear or become totally different from the time series based on homogenised data. All negative (dry) breaks of each month and station, however, occurred in more recent decades of the 20th century, according to both homogeneous and original series.

Due to their coarse spatial resolution, the results from global climate models (GCM) are not capable to provide detailed regional estimations of future climate conditions. The 10-25 km horizontal resolution regional climate models (RCM) nested into GCMs are expected to improve the regional climate scenarios for the European subregions. Expected regional climate change in the Carpathian basin (located in Central/Eastern Europe) is modelled by four different RCMs. (1) Model PRECIS was developed at the UK Met Office, Hadley Centre. (2) Model RegCM was developed by Giorgi et al., it is available from the ICTP (International Centre for Theoretical Physics). (3) Model REMO was developed by the Max Planck Institute for Meteorology, Hamburg. (4) Model ALADIN/Climate was developed by Météo France on the basis of the internationally developed ALADIN modelling system. The latter one is a spectral model, while the other three RCMs use gridpoint derivatives. The horizontal resolution of the model experiments are 10 km in case of RegCM and ALADIN/Climate, and 25 km in case of PRECIS and REMO. Two of the RCMs (RegCM and PRECIS) are run by the Department of Meteorology, Eötvös Loránd University, Budapest, the other two RCMs are run by the Hungarian Meteorological Service: ALADIN/Climate and REMO. First, control runs of RegCM, PRECIS, REMO and ALADIN are compared for the 1961-1990 period using boundary conditions from the European Centre for Medium-Range Weather Forecast (ECMWF) reanalysis datasets (ERA-40). For the validation, monthly data sets of the Climate Research Unit (CRU) of the University of East Anglia are used. Then, future climate of the Carpathian basin have also been simulated by all RCMs: (1) PRECIS experiments are accomplished for 2071-2100 using A2 and B2 emission scenarios, (2) RegCM and ALADIN/Climate experiments are accomplished for 2021-2050 and 2071-2100 using A1B emission scenario, and (3) REMO experiments are accomplished for 1951-2050 using A1B emission scenario. Results of the future climate simulations are compared and evaluated.

Heat wave events are important temperature-related climatological extremes due to their impacts on human health. In the future, they are very likely to occur more frequently and more intensely not only in the Carpathian Basin, but in most regions of the world because of global warming. In order to develop adaptation and mitigation strategies on local scale, it is essential to analyze the projected changes related to heat waves. In Hungary, three categories of heat wave warning are applied. They are associated to the daily mean temperature values. (i) Warning category 1 is issued when the daily mean temperature is larger than 25 °C. (ii) Warning category 2 is issued when the daily mean temperature for at least 3 consecutive days is larger than 25 °C. (iii) Warning category 3 is issued when the daily mean temperature for at least 3 consecutive days is larger than 27 °C. In this poster, frequency of these conditions are analyzed using regional climate model experiments of model RegCM with 10-km horizontal resolution adapted at the Department of Meteorology, Eotvos Lorand University in the frame of the CECILIA EU-project. The model RegCM is a 3-dimensional, sigma-coordinate, primitive equation model, and it was originally developed by Giorgi et al. Currently, it is available from the ICTP (International Centre for Theoretical Physics). The initial and lateral boundary conditions of the fine-resolution experiments have been provided by the global climate model ECHAM for the A1B emission scenario for three different time slices (1961-1990, 2021-2050, and 2071-2100).

A fuzzy rule-based technique is used for modelling the relationship between climatic forcing and droughts in a Central/Eastern European country, Hungary. Two types of climatic forcing'called premises'are considered: atmospheric circulation patterns (CP) and El Niño Southern Oscillation (ENSO). Both the Hess-Brezowsky CP types and ENSO events influence the occurrence of droughts, but the ENSO signal is relatively weak in a statistical sense. The fuzzy rule-based approach is able to learn the high space—time variability of monthly Palmer Drought Severity Index (PDSI) and results in a proper reproduction of the empirical frequency distributions. The “engine” of the approach, the fuzzy rules, are ascertained from a subset called the learning set of the observed time series of premises (monthly CP frequencies and Southern Oscillation Index) and PDSI response. Then an independent subset, the validation set, is used to check how the application of fuzzy rules reproduces the observed PDSI.Une technique à base de règles floues est utilisée pour modéliser la relation entre le forçage climatique et les sécheresses dans un pays d'Europe de l'est centrale: la Hongrie. Deux types de forçage climatique'appelés des prémisses'sont pris en compte: des schémas de circulation atmosphérique et l'oscillation australe El Niño (ENSO). Les schémas de circulation atmosphérique du type de ceux de Hess-Brezowsky, de même que les épisodes d'ENSO, influencent l'occurrence de sécheresses, mais le signal ENSO est statistiquement faible. La modélisation à base de règles floues permet d'appréhender la grande variabilité spatio-temporelle de l'indice mensuel de sévérité de sécheresse de Palmer, ce qui conduit à s'approcher de façon adéquate des distributions empiriques de fréquence. Les règles floues constituent le “moteur” de la méthode. Elles sont obtenues à partir d'un sous-ensemble, appelé série d'apprentissage, des séries temporelles des prémisses observées (les fréquences mensuelles des schémas de circulation atmosphérique et l'indice d'oscillation australe) et de la variable de réponse, l'indice de Palmer. Par la suite, une sous-série indépendante, la série de validation, est utilisée pour vérifier comment la mise en œuvre des règles floues permet de reproduire la série observée de l'indice de Palmer.

The IPCC Third Assessment Report (2001) suggests that Southern and Central European countries may become highly vulnerable to global warming. In the frame of the Hungarian national climate change program, adaptation of regional models with fine horizontal resolution (10-25 km) is in progress. Since detailed simulations and evaluation of the final results are not available yet for the Carpathian Basin, results of the European project PRUDENCE are presented and discussed here (with 50 km resolution) for 2071-2100. In the second part of the paper, preliminary results of the climate model adaptation using HadCM3/PRECIS (developed at the Hadley Climate Centre of the UK Met Office) are evaluated. Testing runs for the Central/Eastern European region are validated at the Department of Meteorology, Eötvös Loránd University. REGIONÁLIS ÉGHAJLATI BECSLÉSEK A KÁRPÁT-MEDENCE TÉRSÉGÉRE Összefoglalás Az IPCC 2001-es Harmadik Helyzetértékelő Jelentése a veszélyeztetett területek közé sorolja többek között a Földközi-tenger vidékét, s Közép-Kelet-Európa országait. 2004-ben zárult le a PRUDENCE európai uniós projekt, mely a klímaváltozások Európát fenyegető kockázatát és következményeit volt hivatott elemezni. E projekt keretében a 21. század utolsó három évtizedére kapott évszakos átlaghőmérséklet és csapadékösszeg becsléseket mutatjuk be, s hasonlítjuk össze Európára, illetve a Kárpát-medencére. A cikk második részében a beágyazott finomabb felbontású dinamikai modell-adaptációs kísérleteink eddigi eredményeit foglaljuk össze. A Brit Meteorológiai Szolgálat Hadley Klíma-központjában kifejlesztett HadCM3 globális klímamodellbe ágyazott PRECIS regionális modellel kívánunk becsléseket adni a 21. század várható hazai éghajlatára. A modellel lefedhető térség kiterjedésének felső korlátja 5000×5000 km 2 . A választható rácsfelbontás 25 vagy 50 km (jelen kísérleteink során mi a 25 km-es rácsfelbontást alkalmaztuk). A modellfejlesztés célja az volt, hogy nemzeti éghajlatváltozási hatástanulmányok készítéséhez adjanak közre egy eszközt, mely jól alkalmazható érzékenységvizsgálatokhoz, regionális alkalmazkodási programok kidolgozásához. A program adaptálása megtörtént, kiválasztottuk vizsgálataink célterületét, Közép-és Dél-Európa térségére elkezdtük a modell validálását, s a tesztfutásokat. Jelenleg a modell széleskörű tesztelése folyik Közép-Kelet-Európa térségére az ERA40 adatbázis felhasználásával.

Since human and natural systems may be especially affected by changes of extreme climate events, the main objective of our research is to detect the possible changes of intensity and frequency of these extreme events. Several climate extreme indices are analyzed and compared for Central/Eastern Europe (focusing on Hungary) for the 20th century based on the guidelines suggested by the joint WMO-CCl/CLIVAR Working Group on climate change detection. These climate extreme indices include the numbers of severe cold days, winter days, frost days, cold days, warm days, summer days, hot days, extremely hot days, cold nights, warm nights, hot nights, the intra-annual extreme temperature range, the heat wave duration, the number of wet days (using several threshold values defining extremes, i.e., 10 mm and 20 mm), the maximum number of consecutive dry days, the highest 1-day precipitation amount, the greatest 5-day rainfall total, the simple daily precipitation intensity, the numbers of moderate wet days and very wet days, the annual fraction due to extreme precipitation events, etc. Therefore, daily maximum, minimum and mean temperature observations (from 13 stations) and daily precipitation amounts (from 31 stations) are used in the present statistical analysis. Our results suggest that similarly to the global and continental trends, regional temperature of Central/Eastern Europe has become warmer during the second half of the 20th century. Specifically, the strongest increasing tendency is detected in case of the annual numbers of hot days, summer days, warm days, warm nights, and the heat wave duration index. Before this warming period in the last quarter of the 20th century, most of the indices exhibit a cooling period until the middle of the 1970's. Furthermore, regional intensity and frequency of extreme precipitation has increased (as shown by the annual fraction due to extreme precipitation events, and the numbers of moderate wet days, very wet days, and very heavy precipitation days) between 1976 and 2001, while the total precipitation has decreased (as shown by numbers of precipitation days exceeding 0.1 mm, 1 mm, and 5 mm) in the region.

In order to cover a millennium-long period in climatological studies, several types of information must be taken into consideration. Beyond the regular meteorological observations, historical documentary data may serve as a basic source for the past centuries. For the Carpathian basin, Réthly collected historical documents containing meteorology-related information. In order to facilitate the analysis of this documentary collection, a special code system using hierarchical subclasses has been defined and applied to approximately 15 000 collected climatological items. The spatial and temporal distributions of temperature- and precipitation-related climate events and extremes have been evaluated using settlement and subregional scales. Also, the geographical distribution of extreme climatological events has been mapped. Annual and seasonal time series have been analysed for the Carpathian basin and compared with other reconstructed temperature and precipitation index time series from other geographical locations outside the Carpathian basin.

Four regional climate models (RCMs) were adapted in Hungary for the dynamical downscaling of the global climate projections over the Carpathian Basin: (i) the ALADIN-Climate model developed by Météo France on the basis of the ALADIN short-range modelling system; (ii) the PRECIS model available from the UK Met Office Hadley Centre; (iii) the RegCM model originally developed at the US National Center for Atmospheric Research, is maintained at the International Centre for Theoretical Physics in Trieste; and (iv) the REMO model developed by the Max Planck Institute for Meteorology in Hamburg. The RCMs are different in terms of dynamical model formulation, physical parameterisations; moreover, in the completed simulations they use different spatial resolutions, integration domains and lateral boundary conditions for the scenario experiments. Therefore, the results of the four RCMs can be considered as a small ensemble providing information about various kinds of uncertainties in the future projections over the target area, i.e., Hungary. After the validation of the temperature and precipitation patterns against measurements, mean changes and some extreme characteristics of these patterns (including their statistical significance) have been assessed focusing on the periods of 2021-2050 and 2071-2100 relative to the 1961-1990 model reference period. The ensemble evaluation indicates that the temperature-related changes of the different RCMs are in good agreement over the Carpathian Basin and these tendencies manifest in the general warming conditions. The precipitation changes cannot be identified so clearly: seasonally large differences can be recognised among the projections and between the two periods. An overview is given about the results of the mini-ensemble and special emphasis is put on estimating the uncertainties in the simulations for Hungary.

One of the most current challenges of cities in the changing environment of our century is the transport. Increasing traffic load of the growing population of cities has many inconvenient consequences. This is why orbital motorways around big cities are essential to decrease the traffic load of the encircled cities. For analyzing the potential impact of climate change in this area, outputs of PRECIS, a regional climate model, were used. When planning the lifetime of roads, environmental conditions (such as climate and soil type) are the dominant factors besides the expected traffic load. Expected climate change, therefore, may influence not only the expected lifetime of roads, but also the frequency of reconstructions, which results other direct and external costs. In this paper, we make an attempt to quantify the climate change driven vulnerability for the most critical summer period of asphalt paved part of the orbital motorway around Budapest, the capital city of Hungary for 2071-2100 using A2 and B2 SRES scenarios of IPCC. Model PRECIS have been adapted for the Carpathian Basin at the Department of Meteorology, Eötvös University. This model is a hydrostatic regional climate model HadRM3P developed at the UK Met Office, Hadley Centre, and nested in HadCM3 global climate model. It uses 25 km horizontal resolution transposed to the Equator and 19 vertical levels with sigma-coordinates.

Changes in large-scale circulation patterns over the North-Atlantic-European region are presented and analyzed for the 20th century. First, changes in decadal frequency of Hess-Brezowsky macrocirculation patterns (MCP) are evaluated for the period between 1881 and 2000. Frequency of several MCP types increased or decreased considerably during these 120 years, which may be explained by large-scale changes in circulation characteristics, e.g. by changes in cyclone activity in the different regions. Therefore, cyclone center identification and cyclone tracks and intensity analysis have been accomplished on the basis of the European Centre for Medium-range Weather Forecast (ECMWF) reanalysis data sets (ERA-40) on a 2.5° horizontal resolution grid for the period between 1957 and 2002. Results suggest that both the number of midlatitude cyclones and the cyclone activity increased considerably in the North-Atlantic-European region, especially in the northwestern part of the domain.