Data quality control and homogenization of air temperature and precipitation series in the area of the Czech Republic in the period 1961–2007

Quality control and homogenization has to be undertaken prior to any data analysis in order to eliminate any erroneous values and non climatic biases in time series. In this work we describe and then apply our own approach to data quality control, combining several methods: (i) by applying limits derived from interquartile ranges (ii) by analyzing difference series between candidate and neighbouring stations and (iii) by comparing the series values tested with "expected'' values – technical series created by means of statistical methods for spatial data (e.g. IDW, kriging). <br><br> Because of the presence of noise in series, statistical homogeneity tests render results with some degree of uncertainty. In this work, the use of various statistical tests and reference series made it possible to increase considerably the number of homogeneity test results for each series and thus to assess homogeneity more reliably. Inhomogeneities were corrected on a daily scale. <br><br> These methodological approaches are demonstrated by use of the daily data of air temperature and precipitation measured in the area of the Czech Republic. Series were processed by means of developed ProClimDB and AnClim software (<a href="http://www.climahom.eu" target="_blank">http://www.climahom.eu</a>)

Observed spatiotemporal characteristics of drought on various time scales over the Czech Republic

10.1007/s00704-013-0908-yThis paper analyses the observed spatiotemporal characteristics of drought in the Czech Republic during the growing season (April to September) as quantified using the Standardised Precipitation Evapotranspiration Index (SPEI) on various time scales. The SPEI was calculated for various lags (1, 3, 6, 12, and 24 months) from monthly records of mean temperature and precipitation totals using a dense network of 184 climatological stations for the period 1961¿2010. The characteristics of drought were analysed in terms of the temporal evolution of the SPEI, the frequency distribution and duration of drought at the country level, and for three regions delimited by station altitude. The driest and the wettest years during the growing season were identified. The frequency distribution of the SPEI values for seven drought category classes (in per cent) indicates that normal moisture conditions represent approximately 65 % of the total SPEI values for all time scales in all three regions, whereas moderate drought and moderate wet conditions are almost equally distributed around 10.5 %. Differences in extremely dry conditions (5 %) compared with extremely wet conditions (1.5 %) were observed with increasing SPEI time scales. The results of the non-parametric Mann¿Kendall trend test applied to the SPEI series indicate prevailing negative trends (drought) at the majority of the stations. The percentage of stations displaying a significant negative trend for the 90, 95, 99, and 99.9 % confidence levels is approximately 40 %. An Empirical Orthogonal Functions (EOF) analysis was used to identify the principal patterns of variability of the SPEI during the growing season that accounted for the highest amount of statistical variance. The variance explained by the leading EOF range 66 t

Spatial and temporal evolution of drought conditions at various time scales in the Czech Republic during growing period

This paper analyzes the characteristics of spatial evolution of the standardized precipitation evapotranspiration index (SPEI) at various time scales during the growing period (April-September) over the Czech Republic. The SPEI was calculated from monthly records of mean temperature and precipitation totals measured at a dense network of 184 climatological stations for the period 1961-2010. Using various lags, 1, 3, 6, 12, and 24 months. The drought at these time scales is relevant for agricultural, hydrological, and socio-economic impacts, respectively. The study refers to the warm season of the year (from April to September). The principal modes of variability of the SPEI calculated at these five time scales were identified by using the empirical orthogonal functions (EOF) analysis. The explained variance of the leading EOF ranges between 71 and 61% as the time scale for calculating the SPEI increases from 1 to 24 months. The explained variance of EOF2 and EOF3 ranges between 5 and 9%, and 4 and 6%, respectively, as the SPEI is calculated for 1-24 months. With a few exceptions at stations at the highest altitudes, the spatial coefficients of the EOF1 for all SPEI time scales have the same sign over the country's territory. Based on the spatial distribution of the spatial coefficients of EOF2 and EOF3, at all SPEI time scales we have identified three climatically homogenous regions, corresponding to the altitudes below 400 m, between 401 and 700 m, and above 700 m. This regionalization corresponds to some extend to that which was previously used in other studies. These three regions reflect different land use types corresponding to: (i) mostly intensive agriculture, (ii) less intensive agriculture, and (iii) limited agricultural production and mostly forested, respect

Drivers of treeline shift in different European mountains

A growing body of evidence suggests that processes of upward treeline expansion and shifts in vegetation zones may occur in response to climate change. However, such shifts can be limited by a variety of non-climatic factors, such as nutrient availability, soil conditions, landscape fragmentation and some species-specific traits. Many changes in species distributions have been observed, although no evidence of complete community replacement has been registered yet. Climatic signals are often confounded with the effects of human activity, for example, forest encroachment at the treeline owing to the coupled effect of climate change and highland pasture abandonment. Data on the treeline ecotone, barriers to the expected treeline or dominant tree species shifts due to climate and land use change, and their possible impacts on biodiversity in 11 mountain areas of interest, from Italy to Norway and from Spain to Bulgaria, are reported. We investigated the role of environmental conditions on treeline ecotone features with a focus on treeline shift. The results showed that treeline altitude and the altitudinal width of the treeline ecotone, as well as the significance of climatic and soil parameters as barriers against tree species shift, significantly decreased with increasing latitude. However, the largest part of the commonly observed variability in mountain vegetation near the treeline in Europe seems to be caused by geomorphological, geological, pedological and microclimatic variability in combination with different land use history and present socio-economic relation Vegetation zone shift · Climate change · Climate models · Treeline ecotone · European mountains · Ecosystem service