Hybrid Approach to Delineation of Homogeneous Regions for Regional Precipitation Frequency Analysis
Regional frequency analysis of heavy precipitation amounts based on the estimation of the parameters of a regional distribution function using L-moments is adopted for the specific geographical-climatological settings of Slovakia. The paper focuses on the first step of the regional L-moment algorithm (Hosking, Wallis, 1997), which is the delineation of homogeneous regions. Objective and process-based logical pooling techniques are used to form homogeneous pooling groups of rainfall gauging stations for regional frequency analysis of k-day precipitation amounts (k = 1 to 5 days). Even though the delineation of homo-geneous regions by means of objective methods is generally accepted and recommended in the literature, it is concluded here that such a pooling of similar sites should not be carried out automatically in precipitation analysis. Instead, a combination of physical/geomorphological considerations and objective methods should be preferred.
In the context of climate change, scientists discuss the relevant reference periods for the assessment of changes in climate. Recently, many studies have been published comparing recent conditions with the last reference period 1961–1990. In this paper, the trends of annual, seasonal and monthly average air temperature, as well as annual, seasonal and monthly precipitation totals in Slovakia, are presented to point out changes which will probably show up in the next reference period 1991–2020. In the second part of paper, changes in the climate regions in Slovakia are analysed, comparing spatial distributions in the period 1961–1990 and in the period 1961–2010.
Knowledge on snowfall and precipitation variability is one of the most important information about climate changes. The presented study is based on daily data for precipitation totals and new snow cover depths and monthly air temperature from 29 meteorological stations in Slovakia. The aim is to determine to what extent the change of monthly air temperature mean affects the snowfall in the mountainous area of Slovakia. In order to achieve the aim of the research work, the snow days and precipitation days (SD/PD) ratio is calculated for the months from October to April and the trend is investigated. On the basis of correlation analysis it is determined that the main factor for changes in the SD/PD ratio is the mean monthly air temperature while precipitation plays an important role only for the stations with the altitude above 1300 m. Spatial distribution of the changes in the SD/PD ratio for the winter time (December - January - February) during the period 1981-2011 was investigated by cluster analyses. The results show that the stations are grouped according to their geographical location and relief of the territory.
The impacts of summer heat events on the mortality of the Slovak population, both in total and for selected population sub-groups, are the foci of this study. This research is the first of its kind, focusing on a given population, and therefore one priority was to create a knowledge base for the issue and to basically evaluate existing conditions for the heat-mortality relationship in Slovakia. This article also aims to fill a void in current research on these issues in Europe. In addition to overall effects, we focused individually on the major historical heat events which occurred in the summers of 2007, 2010 and 2012. During the heat events, a non-negligible negative response in mortality was recorded and fatal effects were more pronounced during particularly strong heat events and periods which lasted for two or more days. In general, females and the elderly were the most sensitive groups in the population and mortality was characterized by several specific effects in individual population groups. The most extreme heat periods were commonly followed by a deficit in mortality, corresponding to a short-term mortality displacement, the pattern of which varied in specific cases. In general, displaced mortality appeared to compensate for a large part of heat-induced excess deaths.
The heterogeneity of water flow and solute transport was assessed during radioactive tracer infiltration experiment in a black clay loam soil using modified methods to estimate the effective cross section (ECS) and the degree of preferential flow (DPF). The results of field and numerical experiments showed that these parameters characterized the heterogeneity of water flow in the soils unequivocally. The ECS decreases non-linearly and the DPF increases linearly with an increase of the bypassing ratio (ratio of macropore flow rate to total flow rate). The ECS decreased and the DPF increased with depth, which suggests an increase in the heterogeneity of water flow with depth. The plot of the DPF against ECS values calculated from the tracer experiment data was consistent with the relationship obtained by the numerical simulation assuming preferential flow in the neighbourhood of three probes.