Vol. 122, No. 2 * Pages 101–216 * April - June 2018

DOI:10.28974/idojaras.2018.2.1

This paper concerns the relationships between selected circulation indices and air temperature over Southeast Poland between 1871-2010. The geostrophic wind speed and the resultant vorticity were computed based on daily gridded fields of mean sea-level pressure over an area defined from 5°20’ to 40°20’E and from 41°15’ to 61°15’N. The highest daily mean geostrophic wind speed over Southeast Poland is observed from December to February. In turn, the maximum (positive) values of the resultant vorticity occur in April and May, while the minimum (negative) values are observed in January. Mean air temperature from November to February has a strong positive correlation with the geostrophic wind speed. Moreover, the occurrence of the highest coefficients regarding the correlation between the geostrophic wind speed and air temperature in winter as well as the NAO index was recorded at the beginning of the 21st century. This suggests that the range of impact of sea-level pressure distribution over the North Atlantic on the winter air temperature over Southeast Poland may have increased over the last decades. One of the causes may be an eastward shift of the position of the center of the Icelandic Low and the Azores High in the period from December to February.

DOI:10.28974/idojaras.2018.2.2

In this study, we evaluated three conceptually similar ozone gas deposition models. These dry deposition models are frequently used with chemical transport models for calculations over large spatial domains. However, large scale applications of surface-atmosphere exchange of reactive gases require modeling results as accurate as possible to avoid nonlinear accumulation of errors in the spatially representative results. In this paper, model evaluation and comparison against measured data over a coniferous forest at Niwot Ridge AmeriFlux site (Colorado, USA) is carried out. At this site, no previous model calibration took place for any of the models, therefore, we can test and compare their performances under similar conditions as they would perform in a spatial application. Our results show systematic model errors in all the three cases, model performance varies with time of the day, and the errors show a pronounced seasonal pattern as well. The introduction of soil moisture content stress in the model improved model performance regarding the magnitude of fluxes, but the correlation between measured and modeled ozone deposition values remains low. Our results suggest that ozone dry deposition model results should be interpreted carefully in large scale applications, where the accuracy can vary with land cover sometimes are biased.

DOI:10.28974/idojaras.2018.2.3

Heavy rainfalls and consequent floods are the most important extreme events in Central Europe in terms of frequency and economic losses. The purpose of the study is to evaluate regional extreme precipitation events in the Polish Carpathian Mountains as well as to determine the circulation basis for these events. Extreme precipitation values were identified based on daily precipitation totals measured at almost 70 weather stations in the Polish Carpathians between 1951 and 2015. The analysis concentrates on daily mean areal precipitation totals in excess of 100 mm per day as well as 50 and 30 mm, which causes flooding in the Carpathians. All extreme precipitation data were analyzed from a synoptic perspective, with special attention paid to pressure patterns over Central Europe. The analysis confirms that the heaviest rainfalls are affected by the situations with the N-NE airflow. However, analyses with the application of the upper tropospheric data brought some new findings on the precipitation extreme topic. It turned out that most cases with significant rains occurred when the mid-tropospheric advection was from the southern sector (during the typical N and NE advections in the lower part).

DOI:10.28974/idojaras.2018.2.4

Anopheles maculipennis is one of the potential vectors of Plasmodium vivax caused malaria in Europe. Although potential malaria vectors are present in the continent, malaria was eradicated in historical times and recently absent in Central and East Europe and the North Balkan. Climate change may trigger the re-emergence of malaria in Europe positively affecting the seasonal patterns of the potential Anopheline vectors. The increasing length of the larva season of mosquito vectors is one of the risk factors of the re-emerging of malaria. The monthly relative abundance values of the larvae of Anopheles maculipennis were modeled for the reference period 1961–1990 and the periods 2011–2040 and 2041–2070 based on the REMO climate model for Central and East Europe and the North Balkan region. Strong, significant correlation (r²=0.94, p<0.0001) was found between the monthly relative abundances of larvae and monthly mean air temperature values in Hungary between March and November. The threshold of the larval activity of Anopheles maculipennis was found to be about 4 °C. Comparing the modeled relative abundances for 1961–1990, 2011–2040, and 2041–2070, April and October months showed the most notable changes. The model predicts that in Southeast Hungary, East Croatia, North Serbia, South Romania, and North Bulgaria, the main season will increase by +1 to +2 months to the period of 2041–2070 comparing to the reference period. The model also indicates that the complete main Anopheles maculipennis larva season of the mosquito will increase by two months in Southeast Hungary and at least 1 month in the other parts of the south Pannonian Ecoregion, in the North Balkan region including South Romania and North Bulgaria for 2041–2070.

DOI:10.28974/idojaras.2018.2.5

Bulgaria is situated in a geographical area with high frequency and intensity of thunderstorms and hail events. Like in many other countries, an upward trend of weather-induced damage has been observed during the last 15 years in Bulgaria. Much of it was caused by extreme weather events such as torrential precipitation associated with severe thunderstorms or/and wind storms. The series of flash floods and extreme hail storms, which hit Bulgaria in the warm half of 2014, were in line with that trend.
On July 8, 2014, three supercell storms developed over West Bulgaria and heavily impacted urban areas in the afternoon. The extremely strong hail storms over Sofia and Montana were accompanied by strong wind gusts (about 85 km h^–1) and torrential rain. The giant hail stones in Sofia had diameter of up to 10 cm and irregular shape. The severe hail and rain, and very strong wind caused substantial damage to infrastructure, buildings, vehicles, and agriculture. More than 40 people were injured by hail stones or collaterally by broken windows. One man was killed by a fallen tree. In Sofia alone, the reported damage was worth more than 100 million euro according to data from insurance companies.
The paper presents the analysis of the evolution of the convective clouds based on radar data. The Doppler radar data revealed the existence of a mesocyclone, mesoanticyclone, microburst, and three-body scatter signature. The cloud top reached up to 17 km, and the maximum radar reflectivity factor was 69–71 dBZ. Analysis of the available radiosounding data, simulation with a numerical model, and the synoptic patterns are also presented.

DOI:10.28974/idojaras.2018.2.6

Parametric methods (linear trend, t-test for slope) for analyzing time series are the simplest methods to get insight to the changes in a variable over time. These methods have a requirement for normal distribution of the population that can be a limit for application. Non-parametric methods are distribution-free methods, and investigators can have a more sophisticated view to the variable tendencies in time series. 144-year-long time series of precipitation data measured at the meteorological station in Keszthely, Hungary (latitude: 46°44′, longitude: 17°14′, elevation: 124 m above Baltic sea level) were analyzed by Mann-Kendall trend test for detecting tendencies in the time series. Sen’s slope estimator was applied to estimate the slope of the linear changes. In average, 44 mm decline can be shown for 100 years in the annual sum, 29.7 mm and 25.7 mm in the precipitation sum of spring and autumn (in 100 years), respectively. The rainfall sum of winter increased by 15.4 mm. Sums of April, May, and October declined by 10.8 mm, 13 mm, and 20.9 mm, respectively, according to one-tailed Mann-Kendall tests. These results were compared to the previous results of the authors carried out by parametric methods. Results of two-tailed tests of parametric and non-parametric methods are easily comparable. Parametric method (linear trend) proved significant decreasing tendencies for spring, April, and October. Non-parametric Mann-Kendall tests show significant declining tendencies for spring, autumn, and October.