The article presents the results of precipitation and aerosol (PM10) data analyses in Slovenia. Analyses of rainfall data for some areas of Slovenia, such as the Ljubljana Basin, Zasavje, Šalek Valley, Celje Basin, and the coastal area, suggest that rain on the weekend is more frequent than on weekdays; nevertheless, these deviations are not statistically significant. A comparison of three separate decades showed that the pattern of weekly rainfall in the 21st century is different than that in the last period of the 20th century. The weekly cycle of PM10 for the considered stations is quite similar to that of some of the more contaminated regions of the world. Furthermore, the connection between PM10 and precipitation in most of the analyzed cases was statistically significant. ACT A GEOGRAPHICA SLOVENICA GEOGRAFSKI ZBORNIK 2018 58 2 0101661851779 ISSN 1581-6613 A CT A GEO GR APHICA SL O VENICA • GEO GR AFSKI ZB ORNIK • 58-2 • 2018 A CT A GEO GR APHICA SL O VENICA GEO GR AFSKI ZB ORNIK 58-2 • 2018 Contents Ivan Čanjevac, Danijel OrešIć Changes in discharge regimes of rivers in Croatia 7 jaka PleČkO, nejc Bezak, Marjeta škaPIn rugelj, Mojca šraj Does it really rain more often on weekends than on weekdays: a case study for Slovenia 19 katja vIntar Mally Regional Differences in Slovenia from the Viewpoint of Achieving Europe’s Sustainable Development 31 Petra rus, janez nareD, štefan BOjnec Forms, areas, and spatial characteristics of intermunicipal cooperation in the Ljubljana Urban Region 47 jadwiga gałka, annaWarych-juras Front cover photography: Alpine environment has witnessed changes in discharge regimes that depend on the changes in precipitati on and temperature regimes, land use and human influence (photograph: Matej Lipar). Fotografija na naslovnici:Pretočni režimi se v alpskih pokrajinah spreminjajo zaradi sprememb v padavinskem in temperaturnem režimu ter sprememb rabe zemljišč in človeških vplivov (fotografija: Matej Lipar). 58-2-uvod_00p_uvod49-1.qxd 12.9.2017 8:58 Page 4 Acta geographica Slovenica, 58-2, 2018, 19–30 DOES IT REALLY RAIN MORE OFTEN ON WEEKENDS THAN ON WEEKDAYS? A CASE STUDY FOR SLOVENIA Jaka Plečko, Nejc Bezak, Marjeta Škapin Rugelj, Mojca Šraj Climate conditions in Slovenia are changing as indicated by an increasing number of extreme events. NEJC BEZAK 58-2_02p_2255-Jaka Plecko_acta49-1.qxd 12.9.2017 8:59 Page 19 Jaka Plečko, Nejc Bezak, Marjeta Škapin Rugelj, Mojca Šraj, Does it really rain more often on weekends than on weekdays? … DOI: https://doi.org/10.3986/AGS.2255 UDC: 556.12(497.4) 504.5:502.3(497.4) COBISS: 1.01 Does it really rain more often on weekends than on weekdays? A case study for Slovenia ABSTRACT: The article presents the results of precipitation and aerosol (PM10) data analyses in Slovenia. The main aim of this study was to test if it really rains more often on weekends than on weekdays in Slovenia, and to find out which parts of Slovenia are tho se where rainfall distribution during the week is significantly non-uniform. Other aims of the study were as follows: (i) to analyze the weekly rainfall dis- tribution in Slovenia and the differences among seasons, (ii) to compare weekly rainfall patterns among various 10-year periods (1980–2014), and (iii) to analyze the concentration of PM 10 particles in the air and how this relates to the weekly rai nfall pattern. The main advantage of the χ 2 test is that it can be applied to both continuous and discrete variables (Haan 2002) and is mostly used for hypothesis testing about distribution of samples (Turk 2012). In our study the following null hypothesis was used (H0): rain- fall distribution during the week is uniform, while the alternative hypot hesis was (H A ): rainfall distribution Acta geographica Slovenica, 58-2, 2018 21 58-2_02p_2255-Jaka Plecko_acta49-1.qxd 12.9.2017 8:59 Page 21 Jaka Plečko, Nejc Bezak, Marjeta Škapin Rugelj, Mojca Šraj, Does it really rain more often on weekends than on weekdays? These results are in accordance with other studies that concluded that non-uniform weekly rainfall distribution is more explicit for more polluted areas (Gongetal. 2007; Stjern 2011). The Šalek Valley and Zasavje are regarded as areas with relatively high pollution, Ljubljana Basin is the largest urban area in Slovenia , and the pollution at the Portorož station can be attributed to the influence of Trieste, Italy. Acta geographica Slovenica, 58-2, 2018 23 58-2_02p_2255-Jaka Plecko_acta49-1.qxd 12.9.2017 8:59 Page 23 Jaka Plečko, Nejc Bezak, Marjeta Škapin Rugelj, Mojca Šraj, Does it really rain more often on weekends than on weekdays? The calculated Pearson's Ljubljana 20 21 22 23 24 25 26 27 Maribor 26 27 28 29 30 31 32 33 34 Celje 24 25 26 27 28 29 30 31 32 Kozina 18 19 20 21 22 23 24 Average daily values Average + st. dev. A –verage st. dev. Mon Tue Wed Thu Fri Sat Sun Mon Tue Wed Thu Fri Sat Sun PM10 concentrations [µg/m3]PM10 concentrations [µg/m3] Mon Tue Wed Thu Fri Sat Sun Mon Tue Wed Thu Fri Sat Sun Figure 3: Weekly distribution of PM10 concentrations at Ljubljana, Maribor, Celje, and Kozina stations. 58-2_02p_2255-Jaka Plecko_acta49-1.qxd 12.9.2017 8:59 Page 27 Jaka Plečko, Nejc Bezak, Marjeta Škapin Rugelj, Mojca Šraj, Does it really rain more often on weekends than on weekdays? Ljubljana. Rao, A.R., Hamed, K.H. 2001: Flood frequency analysis. New York. Schultz, D., M., Mikkonen, S., Laaksonen, A., Richman, M.B. 2007: Weekly precipitation cycles? Lack of evidence from United States surface stations. Geophysical research letters 34-22. DOI: http://dx.doi.org/ 1 0.1029/2007gl031889 Seibert, J., Addor, N., Ewen, T. 2013: Does it really always rain on the weekend? – Weekly precipitation cycles in Switzerland. Geophysical research abstracts 15. Acta geographica Slovenica, 58-2, 2018 29 58-2_02p_2255-Jaka Plecko_acta49-1.qxd 12.9.2017 8:59 Page 29 Jaka Plečko, Nejc Bezak, Marjeta Škapin Rugelj, Mojca Šraj, Does it really rain more often on weekends than on weekdays?