Over the past decades, in the mountainous, hilly and/or urban areas of Hungary several high-intensity storms were followed by severe flash flooding and other hydrologic consequences. The overall aim of this paper was to upgrade the national flash flood susceptibility map of Hungary first published by Czigány et al. (2011). One elementary watershed level (FFSIws) and three settlement level flash flood susceptibility maps (FFSIs) were constructed using 13 environmental factors that influence flash flood generation. FFSI maps were verified by 2,677 documented flash flood events. In total, 5,458 watersheds were delineated. Almost exactly 10% of all delineated watersheds were included into the category of extreme susceptibility. While the number of the mean-based FFSIs demonstrated a normal quasi-Gaussian distribution with very low percentages in the quintile of low and extreme categories, the maximum-based FFSIs overemphasized the proportion of settlements of high and extreme susceptibility. These two categories combined accounted for more than 50% of all settlements. The highest accuracy at 59.02% for class 5 (highest susceptibility) was found for the majority based FFSIs. The current map has been improved compared to the former one in terms of (i) a higher number of conditional factors considered, (ii) higher resolution, (iii) being settlement-based and (iv) a higher number of events used for verification.

This article provides an inventory based on Intergovernmental Panel on Climate Change (IPCC) reports that suggest that changes in the Earth’s system, and primarily atmospheric changes, can be attributed to global warming. The majority of the changes are connected with the phase change of the Earth’s water, changes in glaciers, and the decrease of ice cover. A further indication of this global change can be seen in the change of the annual course of precipitation in many places. In some regions droughts occur more frequently, while in other regions more intense precipitation has been recorded. The effects of global warming in agriculture and forestry are detected in the higher latitudes. The vegetation period starts earlier and the growing season has become longer and longer. Besides the evident rise in temperature that has been detected in meteorological data, significant changes were demonstrated in the observed marine and freshwater biological systems. The detected changes could be consequences of rising water temperature and of decreasing ice cover, of changes of salinity modification, and of change in oxygen content and circulation. After summarising the general signals of climate change, the impact of the warming that has started and that very probably will continue is assessed using the results of climate models and impact studies based on these models. We deal with climate change influences in the hydrosphere separately. Finally, we summarise the possible weather changes in Hungary and in its closest neighbors in the Carpathian Basin. The regional climate models show significant increases in temperature in every season. In the case of precipitation the future is more complicated. The only clear prognosis is that significant decreases could be forecasted in summer. The warming from 1980 to the present in accordance with the global tendency is not only evident in Hungary, but also more severe. The rate of warming is higher in Hungary than the global mean. The average increase for the period 2021–2050 in Hungary is expected to be 1–2°C, for 2071–2100 3–4°C. The average rainfall is expected to decline. However, with respect to the number of rainy days exceeding 20 mm of precipitation, the rain fall intensity shows a slight increase.

Characteristic phenomena in the Pannonian basin during the winter half year are the mist (500-1000 hours/year), the fog (150-300 hours/year) and the cold air pool with high air pollution concentrations. Formation, development and dissipation of fog events are complex processes that are impacted by short- and longwave radiation, condensation and evaporation, turbulent exchange, furthermore fog chemistry. The research presented here aims at exploring the interaction of these processes using field observations. To this end, complex field campaigns were conducted in Budapest (WMO code: 12843) and in the Sió Valley, 6 km away from Siófok (12935) during 1 to 3-month periods in the last three winter half years.Besides air chemistry and standard meteorological variables, the leaf wetness, surface and soil temperature, soil moisture, soil heat flux (Huskeflux), radiation budget components (CNR1) and turbulent fluxes based on eddy covariance (CSAT3, EC150) and gradient methods were measured above the grassland. Time resolutions of measurements for slow sensors were 10 sec or rather 1 minute and for eddy covariance system 10 Hz. The mist and fog periods were detected using a cloud camera (in Sió Valley) and by synoptic observations in Budapest and Siófok.Additional measurements in Budapest were i) the wind speed (U), air temperature (T) and relative humidity (RH) profiles together with Gill sonic anemometer at the top of a 30 m high tower, ii) LUFT CHM 15k ceilometer. SODAR and aviation meteorological measurements were also available from the Budapest Ferenc Liszt International Airport (LHBP) at 8 km distance. Other field experiments were done in the wet leeward Sió Valley in 2018-19 and 2019-20. Vaisala WXT530 sensor, LUFT CHM 15k ceilometer, tethered balloon measurements with GRAW radiosondes and METEK SODAR measurements were also provided as additional information behind the energy budget measurements.Our results confirmed that according to the expectations, we have recorded more foggy situations in the Sió Valley than in Budapest (12843) and Siófok (12935). Radiation and advection type fog events were formed in most cases. The measured RH was above 95 and gradually increased during the onset period of fog. RH was around 100%, fluctuations could be measured less accurately.  Dissipation of the fog is usually characterized by wind intensification and rise in the incoming solar radiation. The data of two field campaigns will be analyzed i) a cold pool situation in Sió Valley in January 2020 and ii) the foggy season 2020-21 in Budapest. The developed complex (micrometeorological, furthermore air and liquid chemistry) database gives opportunity to validate numerical model results (WRF, CHIMERE and detailed box model) and to improve parameterizations of the numerical models.