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Content available remote Temporal variability of precipitation extremes in Estonia 1961-2008
Daily precipitation data from 40 stations are used to investigate the temporal variability of precipitation extremes in Estonia. The period covered is 1961-2008, characterized by a uniformity of observational practice. Precipitation extremes are quantified by yearly and seasonal values of two different parameters: day-count indices based on 95th and 99th percentile thresholds. Trend significance was assessed with the Mann-Kendall test. Results show that the frequency of both indices has increased. No significant negative trends were found. An increase of 15.8 events over the 99th percentile per decade was observed for Estonia. The indices selected for this study may be called "soft" climate extremes, but the number of such events is large enough to allow for meaningful trend analysis in a roughly half-century long time series.
The goal of this work is to determine the concentration variability and the values of selected physical and chemical parameters, including the discharge values for the Plutnica River, as well as the causes for changes in these values. When it comes to physical and chemical water quality, the downstream waters of the Plutnica are freshwaters with elevated chloride concentrations. This is due to the fact that the Baltic Sea acts on shallow groundwater along this part of the coast as well as to periodically occurring saltwater intrusions into inland surface waters. The concentrations of the remaining common ions were fairly stable during the course of the year and their annual variability levels were similar.
Celem niniejszej pracy było ustalenie zmienności stężeń i wartości wybranych wskaźników fizyczno-chemicznych oraz przepływów na rzece Płutnicy, a także określenie przyczyn tych zmian. Pod względem jakości fizyczno-chemicznej wody rzeki Płutnicy w jej dolnym biegu są wodami słodkimi o podwyższonych wartościach stężeń chlorków. Wpływa na to niewątpliwie sąsiedztwo morza, które oddziałuje na płytkie wody podziemne w tej części wybrzeża, a także okresowo występujące zjawisko intruzji wód słonawych drogą powierzchniową. Stężenia pozostałych głównych jonów w ciągu roku charakteryzowały się dużą stabilnością i podobną zmiennością roczną uzyskanych wyników.
The aim o f the studies was to characterize time structure of the real sunshine totals in the Szczecin Lowlands and frequency and variability of number of hours with the sun lasting > 4, > 6 and > 10 h in 2000-2004. The largest daily real sunshine total in the Szczecin Lowlands amounting to 6.6 hours occurs in the first ten days of May, whereas the lowest one, 0.8 h, in the third ten day period of December. During the calendar spring (March-May) a 40% larger number of hours with direct sun radiation is observed as compared to that in autumn (Sept. - Nov.). In March, June and September the real sunshine totals before the noon are larger than those in the afternoon, whereas in December there are no distinct differences between them. An average number of days with real sunshine lasting > 4, > 6 and > 10 h is respectively 141, 97 and 14 and its maximum occurs in May. In spring and summer the frequency of days with the above threshold values is approximate and it amounts on average to about 55, 40 and 10% respectively.
The methods for analysing of temporal variability of air temperature are presented in the paper. Special attention is paid to the application of GIS tools. Being a leading and so-called continuous climatic element, air temperature is the best known climatic parameter and therefore makes a good base for various theoretical and practical studies. It concerns temporal analyses as well as spatial issues. In the recent years spatial analyses using GIS techniques are fairly frequent. However, there is the lack of studies devoted to temporal analyses of this particular climatic element. The paper is an attempt to use average annual and monthly air temperature for the territory of Poland. The data originate from 213 meteorological stations in Poland and in neighbouring areas ansd cover 53 years (1951-2003). The data series studied here are fully homogenous, already checked and verified earlier. Application of GIS methods also requires the use of other layers, so in the study digital terrain model (DTM), hydrographical network as well as administrative information were applied. Elevation plays the most important role in the spatial temperature distribution and determination coefficients even exceed 0.95. In the first phase the traditional, classical characteristics for temporal analysis were applied such as: linear trend, standard deviation, variation coefficient. Spatial distribution of the above mentioned measures is presented on the maps of Poland. The next step is based on the gridded values. They are available for the 10 km resolution and have been created from the air temperature maps formerly constructed by the residual cringing method. Such data enabled detailed temporal air temperature analyses for the territory of Poland as well as for individual regions. Gridded data provided the base for the construction of different diagrams showing absolute and relative temporal variability for particular territories. Digital dimension of all these graphs allows many various calculations indicating the range and intensity of the air temperature variability. The study contains only some examples of the temporal analyses from a large variety of particular cases. They are rather universal, so they can be applied for different climatic elements and for many temporal and spatial scales. That approach can be a good tool for further detailed processing as well as for formulating synthesis. All investigations confirm relatively large warming in the recent years. It concerns the whole Poland with the special regard to the central and western regions. However, due to relatively short period this trend does not allow to formulate further conclusions as to the future long-term tendency. Special attention was paid to the extreme thermal seasons of winter and summer. The results univocally show temperature increase during winter since the last years of 80s of the 20th century and they do not confirm any significant tendency for summer. All these results were received based on traditional (station) data as well as on gridded values. Application of the gridded data is quite important from the practical point and for the perspectives of climate change and variability studies. The obtained results point to the main features of the temporal thermal variability and also indicate a considerable spatial diversity not only in the mountain areas but also on Polish Lowlands. At the same time the examples presented here show that digital maps and diagrams allow for various types of calculating and analysing which may add a prominent practical dimension. The results show that climatologic studies with this kind of methodological approach may have a prior cognitive as well as practical meaning. Applied methods can be also used for other environmental elements.
Content available remote Relative abundance distributions of species : the need to have a new look at them
This paper shows that recent models of relative abundances (RADs) like the log-normal model or sequential breakage or nich apportionment models are not able to describe and explain RADs found in natural communities because they are derived from a classical niche concept and assume strong past or present interspecific competition. None of them refers especially to temporal variability and functional niche dimensions. The present paper identifie three basic features of natural communities (unimodal species-weight distributions, abundance-weight distributions with more or less marked upper boundaries, and species density fluctuations that can be modelled by four different random processes). Modelling communities with these basic features resulted in RADs that only in part could be described by classical models but that had shapes often found in sampling from larger natural communities. No single distribution like the canonical log-normal appeared that may serve as a general null-model but RAD and evolutionary strategy (r- or K selection) seem to be related. The shape of relative abundance distributions was found to depend on the number of species even if all parameter setting of the generating distributions were identical. This indicates that classical evenness indices (that assume independence of species number) might not be appropriate to compare communities with different numbers of species. It appeared that RAD and body weight related community patterns have to be studied together.
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