Jelena Luković

Mapping average annual precipitation in Serbia (1961–1990) by using regression kriging

The appearence of geostatistics and geographical information systems has made it possible to analyze complex spatial patterns of meteorological elements over large areas in the applied climatology. The objective of this study is to use geostatistics to characterize the spatial structure and map the spatial variation of average values of precipitation for a 30-year period in Serbia. New, recently introduced, geostatistical algorithms facilitate utilization of auxiliary variables especially remote sensing data or freely available global datasets. The data from Advanced Spaceborn Thermal Emission and Reflection Radiometer global digital elevation model are incorporated as ancillary variables into spatial prediction of average annual precipitation using geostatistical method known as regression kriging. The R2 value of 0.842 proves high performance result of the prediction of the proposed method.

Spatial analysis of the temperature trends in Serbia during the period 1961–2010

The spatial analysis of annual and seasonal temperature trends in Serbia during the period 1961–2010 was carried out using mean monthly data from 64 meteorological stations. Change year detection was achieved using cumulative sum charts. The magnitude of trends was derived from the slopes of linear trends using the least square method. The same formalism of least square method was used to assess the statistical significance of the determined trends. Maps of temperature trends were generated by applying a spatial regression method to visualize the detected tendencies. The obtained results indicate a negative temperature trend for the period before the change year except for winter and a more pronounced positive trend after the change year. Besides being more pronounced, the vast majority of trends after the change year were also clearly statistically significant. Our estimate of the average temperature trend over Serbia is in agreement with those obtained at the global and European scale. Calculated global autocorrelation statistics (Moran’s I) indicate an apparent random spatial pattern of temperature trends across the Serbia for both periods before and after the change year.

Influence of mg doping on structural, optical and photocatalytic performances of ceria nanopowders

Nanosized Mg-doped ceria powders were obtained by self-propagating room temperature reaction without using surfactants or templates. X-ray diffraction analysis and field emission scanning microscopy results showed that the doped samples are solid solutions with fluorite-type structure and spherical morphology. Raman spectra revealed an increase in the amount of oxygen vacancies with the increase of Mg concentration. This increasing results in a narrowing of the bandgap of CeO2. The photocatalytic performances of the Mg-doped ceria solid solutions were evaluated by decomposing an organic dye, crystal violet under UV irradiation. The Mg-doped ceria solid solutions exhibit significantly better photocatalytic activity than the pure CeO2 and commercial TiO2. The higher first rate constant of the Mg-doped samples demonstrated that they are much more efficient than TiO2 and CeO2 under UV light. Mg 2+ dopant ions and oxygen vacancies play a significant role in the enhancement of photocatalytic performances of the Mg-doped ceria.

Assessment on Temperature Extremes in Montenegro

Montenegro so far has been poorly investigated in terms of climate extremes. The aim of this paper was analysis of extreme temperature indices in the Mediterranean region of Montenegro for the period 1951–2010. Four stations in the coastal area of Montenegro have been analysed Herceg Novi, Ulcinj, Budva and Bar. Due to well known great climate shift occurred in the late 1970 two periods (before 1980 and after 1980) were separately investigated. Six ETCCD indices of temperature extremes have been chosen. Indices and their trends are calculated on annual scale in order to identify possible temperature changes over the coastal region of Montenegro. The trend was analysed using Man-Kendall non parametric test while the slope is estimated using Sen’s slope estimator.

Spatial distribution of interpolation uncertainity: Case study of isotherm map of Serbia (1991-2009)

More widely used geostatistical methods for modeling distributed phenomena requires the evaluation of the quality of the product (maps) obtained by their application. The method of evaluation of uncertainty i.e. quality of the map was described on the example of a map of mean annual air temperature in Serbia for the period from the years 1991 to 2009 that was obtained from a relatively small number of samples for the whole country area (110 meteorological stations). The uncertainty of the map, obtained by kriging interpolation was evaluated by applying a Monte Carlo simulation modeling method. [Projekat Ministarstva nauke Republike Srbije, br. III47014, br. III43007 i br. TR 36009]

The changes of precipitation in Podgorica for period 1951-2010

The global warming and climate change are the actual and challenging topics. Recently there is one question, frequently asked: whether todays climate is changing? The studies of this issues are mainly related to the two the most important climatic elements - air temperature and precipitation amounts. We have done research about temperature variability for Montenegro and the main aim of this paper is analysis precipitation changes for station Podgorica (Montenegro) in the period of sistematic observation - are there changes, to what extent and whether they are significant. According to the results, acumulated precipitation do not show significant changes for annual and seasonal values in the period 1951-2010. The interannual variations of the precipitation (which are characterictic for this climate element) do not show increases in recent times. The component trend shows some changes, but statisticaly insignigficant. The previous results for precipitation conditions in Podgorica are not in accordance with the concept of Intergovermental Panel on Climate Change (IPCC) which predicted a general decerease in precipitation and increase variability on this area.