{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,19]],"date-time":"2026-10-19T03:20:42Z","timestamp":1792380042674,"version":"4.4.0"},"reference-count":67,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2021,8,22]],"date-time":"2021-08-22T00:00:00Z","timestamp":1629590400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Atmosphere"],"abstract":"<jats:p>Air pollution is responsible for many adverse effects on human beings. Thermal discomfort, on the other hand, is able to overload the human body and eventually provoke health implications due to the heat imbalance. Methods: The aim of the presented work is to study the behavior of two bio-climatic indices and statistical characteristics of the air quality index for Sofia city\u2014the capital of Bulgaria for the period 2008\u20132014. The study is based on the WRF-CMAQ model system simulations with a spatial resolution of 1 km. The air quality is estimated by the air quality index, taking into account the influence of different pollutants and the thermal conditions by two indices, respectively, for hot and cold weather. It was found that the recurrence of both the heat and cold index categories and of the air quality categories have heterogeneous space distribution and well manifested diurnal and seasonal variability. For all of the situations, only O3 and PM10 are the dominant pollutants\u2014these which determine the AQI category. It was found that AQI1, AQI2, and AQI3, which fall in the \u201cLow\u201d band, have the highest recurrence during the different seasons, up to more than 70% in some places and situations. The recurrence of AQI10 (very high) is rather small\u2014no more than 5% and concentrated in small areas, mostly in the city center. The Heat index of category \u201cDanger\u201d never appears, and the Heat index of category \u201cExtreme caution\u201d appears only in the spring and summer with the highest recurrence of less than 5% in the city center. For the Wind-chill index category, \u201cVery High Risk\u201d never appears, and the category \u201cHigh Risk\u201d appears with a frequency of about 1\u20132%. The above leads to the conclusion that both from a point of view of bioclimatic and air quality indices, the human health risks in the city of Sofia are not as high.<\/jats:p>","DOI":"10.3390\/atmos12081078","type":"journal-article","created":{"date-parts":[[2021,8,22]],"date-time":"2021-08-22T21:42:12Z","timestamp":1629668532000},"page":"1078","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Computer Simulations of Air Quality and Bio-Climatic Indices for the City of Sofia"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6159-3554","authenticated-orcid":false,"given":"Georgi","family":"Gadzhev","sequence":"first","affiliation":[{"name":"National Institute of Geophysics, Geodesy and Geography\u2014Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 3 1113 Sofia, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2130-392X","authenticated-orcid":false,"given":"Kostadin","family":"Ganev","sequence":"additional","affiliation":[{"name":"National Institute of Geophysics, Geodesy and Geography\u2014Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 3 1113 Sofia, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,8,22]]},"reference":[{"key":"ref_1","unstructured":"World Health Organization (WHO) (2004). Health Aspects of Air Pollution. Results from the WHO Project Systematic Review of Health Aspects of Air Pollution in Europe, 2004, WHO."},{"key":"ref_2","unstructured":"WHO (2000). Fact Sheet Number 187, World Health Organization (WHO)."},{"key":"ref_3","unstructured":"European Parliament (2002). Directive 2002\/3\/EC of 12 February 2002 relating to ozone in ambient air. Off. J. Eur. Communities, L67, 14\u201330."},{"key":"ref_4","unstructured":"(2008). European Parliament: Directive 2008\/50\/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe. Off. J. Eur. Union, L152, 1\u201344."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1233","DOI":"10.1016\/S0140-6736(02)11274-8","article-title":"Air pollution and health","volume":"360","author":"Brunekreef","year":"2002","journal-title":"Lancet"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1093\/bmb\/ldg028","article-title":"Ambient air pollution and health","volume":"68","author":"Katsouyanni","year":"2003","journal-title":"Br. Med Bull."},{"key":"ref_7","unstructured":"WHO (2005). WHO Air Quality Guidelines for Particulate Matter, Ozone, Nitrogen Dioxide and Sulphur Dioxide. WHO Regional Office for Europe. Global Update 2005. Summary of Risk Assessment."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1411","DOI":"10.1289\/ehp.1104108","article-title":"Concentration\u2013Response Function for Ozone and Daily Mortality: Results from Five Urban and Five Rural UK Populations","volume":"120","author":"Atkinson","year":"2012","journal-title":"Environ. Health Perspect."},{"key":"ref_9","first-page":"39","article-title":"Health issues for the population in the town of Pleven related to ambient air pollution","volume":"3","author":"Nikiforov","year":"2002","journal-title":"Probl. Hyg."},{"key":"ref_10","first-page":"15","article-title":"Ambient air quality in the municipality of Rousse and public health risk","volume":"1","author":"Nikiforov","year":"2003","journal-title":"Probl. Hyg."},{"key":"ref_11","first-page":"27","article-title":"Ambient air quality and health risk to the population of the town of Dobrich","volume":"2","author":"Antova","year":"2002","journal-title":"Probl. Hyg."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"628","DOI":"10.1136\/jech.57.8.628","article-title":"Mortality and temperature in Sofia and London","volume":"57","author":"Pattenden","year":"2003","journal-title":"J. Epidemiol. Community Health"},{"key":"ref_13","unstructured":"Starr, C., and McMillan, B. (2010). Human Biology, Brooks\/Cole Cengager Learning."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"98","DOI":"10.1007\/BF01093455","article-title":"Too hot for comfort: The heatwaves in Greece in 1987 and 1988","volume":"34","author":"Giles","year":"1990","journal-title":"Int. J. Biometeorol."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Stathopoulou, M.I., Cartalis, C., Keramitsoglou, I., and Santamouris, M. (2005). Thermal Remote Sensing of Thom\u2019s Discomfort Index (DI): Comparison with In Situ Measurements. Remote Sensing for Environmental Monitoring, GIS Applications, and Geology V, SPIE Remote Sensing.","DOI":"10.1117\/12.627541"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"779","DOI":"10.1007\/s00484-008-0171-6","article-title":"Bioclimatic characterisation of an urban area: A case study in B logna (Italy)","volume":"52","author":"Sajani","year":"2008","journal-title":"Int. J. Biometeorol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"45","DOI":"10.1007\/s10661-008-0726-3","article-title":"Evaluating the urban climate of a typically tropical city of northeastern Brazil","volume":"161","author":"Brito","year":"2010","journal-title":"Environ. Monit. Assess."},{"key":"ref_18","unstructured":"(2021, June 15). Ergonomics of the Thermal Environment\u2014Determination and Interpretation of Cold Stress When using Required Clothing Insulation (IREQ) and Local Cooling Effects. (ISO Standard No. 11079:2007). Available online: https:\/\/www.iso.org\/standard\/38900.html."},{"key":"ref_19","unstructured":"(2021, June 15). Ergonomics of the Thermal Environment\u2014Assessment of Heat Stress using the WBGT (Wet Bulb Globe Temperature) Index. (ISO Standard No. 7243:2017). Available online: https:\/\/www.iso.org\/standard\/67188.html."},{"key":"ref_20","unstructured":"(2021, June 15). Ergonomics of the Thermal Environment\u2014Assessment of Heat Stress using the WBGT (Wet Bulb Globe Temperature) Index. (ISO Standard No. 7933:2004). Available online: https:\/\/www.iso.org\/standard\/37600.html."},{"key":"ref_21","unstructured":"(2021, June 15). Ergonomics of the Thermal Environment\u2014Risk Assessment Strategy for the Prevention of Stress or Discomfort in Thermal Working Conditions. (ISO Standard No. 15265:2004). Available online: https:\/\/www.iso.org\/standard\/26129.html."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"487","DOI":"10.1007\/s00484-016-1228-6","article-title":"A comparison and appraisal of a comprehensive range of human thermal climate indices","volume":"61","author":"Grigorieva","year":"2017","journal-title":"Int. J. Biometeorol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"707","DOI":"10.1080\/00140139.2012.760756","article-title":"Notes on the Implementation of the IREQ Model for the Assessment of Extreme Cold Environments","volume":"56","author":"Palella","year":"2013","journal-title":"Ergonomics"},{"key":"ref_24","unstructured":"Fanger, P.O. (1972). Thermal Comfort: Analysis and Applications in Environmental Engineering, McGraw-Hill."},{"key":"ref_25","first-page":"94","article-title":"Die Thermische Komponente der Stadtklimas","volume":"53","year":"1986","journal-title":"Wiss. Mitt. Meteorol. Inst. Univ. M\u00fcnchen."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"203","DOI":"10.1016\/0957-1272(91)90055-J","article-title":"The extreme heat wave in Athens in July 1987 from the point of view of human biometeorology","volume":"25","author":"Matzarakis","year":"1991","journal-title":"Atmos. Environ. Part B Urban Atmos."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1007\/s004840050051","article-title":"Heat stress in Greece","volume":"41","author":"Matzarakis","year":"1997","journal-title":"Int. J. Biometeorol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"71","DOI":"10.1007\/s004840050118","article-title":"The physiological equivalent temperature\u2014A universal index for the biometeorological assessment of the thermal environment","volume":"43","year":"1999","journal-title":"Int. J. Biometeorol."},{"key":"ref_29","unstructured":"de Dear, R.J., Kalma, J.D., Oke, T.R., and Auliciems, A. (2000). Estimation and Calculation of the Mean Radiant Temperature within Urban Structures. Biometeorology and Urban Climatology at the Turn of the Millennium: Selected Papers from the Conference ICB-ICUC\u201999, Sydney, Australia, 8\u201312 November 1999, UNEP."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"323","DOI":"10.1007\/s00484-006-0061-8","article-title":"Modelling radiation fluxes in simple and complex environments\u2014Application of the RayMan model","volume":"51","author":"Matzarakis","year":"2007","journal-title":"Int. J. Biometeorol."},{"key":"ref_31","unstructured":"Rothfusz, L.P. (2021, August 20). NWS Technical Attachment (SR 90-23), Available online: https:\/\/www.weather.gov\/media\/ffc\/ta_htindx.PDF."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"861","DOI":"10.1175\/1520-0450(1979)018<0861:TAOSPI>2.0.CO;2","article-title":"The assessment of sultriness, Part I: A temperature-humidity index based on human physiology and clothing science","volume":"18","author":"Steadman","year":"1979","journal-title":"J. Appl. Meteorol."},{"key":"ref_33","unstructured":"(2021, August 20). The NCAR Command Language (Version 6.6.2) [Software]. (2019). Available online: https:\/\/www.ncl.ucar.edu\/."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1453","DOI":"10.1175\/BAMS-86-10-1453","article-title":"The new wind chill equivalent temperature chart","volume":"86","author":"Osczevski","year":"2005","journal-title":"Bull. Am. Meteorol. Soc."},{"key":"ref_35","unstructured":"(2019, May 20). Wind Chill Index. Available online: https:\/\/www.canada.ca\/en\/environment-climate-change\/services\/weather-health\/wind-chill-cold-weather\/wind-chill-index.html."},{"key":"ref_36","first-page":"3","article-title":"Heat Risks in Bulgaria during 2003\u20132012 period","volume":"40","author":"Ivanov","year":"2014","journal-title":"Bulg. Geophys. J."},{"key":"ref_37","first-page":"1521","article-title":"Wind chill hazard in Bulgaria during 2003\u20132012 period. Comptes Rendus L\u2019Academie Bulg","volume":"67","author":"Ivanov","year":"2014","journal-title":"Des. Sci."},{"key":"ref_38","unstructured":"Ivanov, V., and Chervenkov, H. (2018). Modelling human biometeorological conditions using meteorological data from reanalysis and objective Analysis\u2014Preliminary results. BGSIAM 2018 Advanced Computing in Industrial Mathematics, Springer."},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Chervenkov, H., Slavov, K., and Ivanov, V. (2018). STARDEX and ETCCDI Climate Indices Based on E-OBS and CARPATCLIM. International Conference on Numerical Methods and Applications, Springer.","DOI":"10.1007\/978-3-030-10692-8_40"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1504\/IJEP.2018.099145","article-title":"Computer simulations of the impact of air pollution on the quality of life and health risks in Bulgaria","volume":"64","author":"Georgieva","year":"2018","journal-title":"Int. J. Environ. Pollut."},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Ivanov, V., and Georgieva, I. (2017, January 6\u20138). Air Quality Index Evaluations for Sofia City. Proceedings of the IEEE EUROCON 2017\u201317th IEEE International Conference on Smart Technologies, Ohrid, North Macedonia.","DOI":"10.1109\/EUROCON.2017.8011246"},{"key":"ref_42","unstructured":"Georgieva, I., and Ivanov, V. (2017, January 9\u201312). Impact of the Air Pollution on the Quality of Life and Health Risks in Bulgaria. Proceedings of the HARMO 2017, 18th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Bologna, Italy."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"162","DOI":"10.1504\/IJEP.2015.074500","article-title":"Numerical study of the air quality in the city of Sofia\u2014Some preliminary results","volume":"57","author":"Georgieva","year":"2015","journal-title":"Int. J. Environ. Pollut."},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Georgieva, I., Gadzhev, G., Ganev, K., Prodanova, M., Syrakov, D., and Miloshev, N. (2015). Numerical Study of the Air Quality in the City of Sofia. 8th Congress of the Balkan Geophysical Society, European Association of Geoscientists & Engineers.","DOI":"10.3997\/2214-4609.201414123"},{"key":"ref_45","unstructured":"Georgieva, I., Gadzhev, G., Ganev, K., Prodanova, M., Syrakov, D., and Miloshev, N. (2014, January 8\u201311). Numerical Study of the Air Quality in the City of Sofia\u2014Some Preliminary Results. Proceedings of the HARMO 2014\u201416th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes 2014, Varna, Bulgaria."},{"key":"ref_46","first-page":"37","article-title":"HPC simulations of the atmospheric composition in Bulgaria and the city of Sofia","volume":"17","author":"Georgieva","year":"2017","journal-title":"Cybern. Inf. Technol."},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Georgieva, I., Gadzhev, G., Ganev, K., and Miloshev, N. (2017, January 5\u20139). Computer Simulations of Atmospheric Composition in Urban Areas some Results for the City of Sofia. Proceedings of the Tenth International Conference on \u201cLarge Scale Scientific Computations\u201d, LSSC2018, Sozopol, Bulgaria.","DOI":"10.1007\/978-3-319-73441-5_52"},{"key":"ref_48","first-page":"167","article-title":"Analysis of Dynamical and Chemical Processes Which form Athmospheric Composition over Bulgaria","volume":"18","author":"Georgieva","year":"2018","journal-title":"Int. Multidiscip. Sci. GeoConference: SGEM"},{"key":"ref_49","unstructured":"Georgieva, I., and Miloshev, N. (2018, January 28\u201331). Computer Simulations of PM Concentrations Climate for Bulgaria. Proceedings of the International Conference on \u201cNumerical Methods for Scientific Computations and Advanced Applications\u201d, NMSCAA\u201918, Hissarya, Bulgaria."},{"key":"ref_50","unstructured":"Shamarock, W.C., Klemp, J.B., Dudhia, J., Gill, D.O., Barker, D.M., Wang, W., Powers, J.G., and A Description of the Advanced Research WRF Version 2 (No (2021, June 15). NCAR\/TN-468+STR), 2017, University Corporation for Atmospheric Research. Available online: http:\/\/www.dtic.mil\/dtic\/tr\/fulltext\/u2\/a487419.pdf."},{"key":"ref_51","unstructured":"(2021, June 15). Available online: https:\/\/rda.ucar.edu\/datasets\/ds083.2\/#!access."},{"key":"ref_52","unstructured":"Byun, D., Ching, J., and Science Algorithms of the EPA Models-3 Community Multi-scale Air Quality (CMAQ) Modeling System (2021, June 15). EPA Report 600\/R-99\/030, Washington, DC, EPA\/600\/R-99\/030 (NTIS PB2000-100561), Available online: https:\/\/cfpub.epa.gov\/si\/si public record report.cfm?Lab=NERL&dirEntryId=63400."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"3789","DOI":"10.1175\/1520-0469(1999)056<3789:DCFIMA>2.0.CO;2","article-title":"Dynamically Consistent Formulations in Meteorological and Air Quality Models for Multiscale Atmospheric Studies part I: Governing equations in a generalized coordinate system","volume":"56","author":"Byun","year":"1999","journal-title":"J. Atmos. Sci."},{"key":"ref_54","unstructured":"(2021, August 20). CEP: Sparse Matrix Operator Kernel Emission (SMOKE) Modeling System, 2003, University of Carolina, Carolina Environmental Programs, Research Triangle Park, North Carolina. Available online: https:\/\/www.cmascenter.org\/smoke\/."},{"key":"ref_55","unstructured":"Denier van der Gon, H., Visschedijk, A., van de Brugh, H., and Droge, R. (2021, August 20). A High Resolution European Emission Data Base for the Year 2005, TNO-Report TNO-034-UT-2010-01895 RPT-ML, Apeldoorn, The Netherlands. Available online: https:\/\/www.umweltbundesamt.de\/sites\/default\/files\/medien\/461\/publikationen\/texte_41_2013_appelhans_e03_komplett_0.pdf."},{"key":"ref_56","first-page":"129","article-title":"The WRF Single-Moment 6-Class Microphysics Scheme (WSM6)","volume":"42","author":"Hong","year":"2006","journal-title":"J. Korean Meteor. Soc."},{"key":"ref_57","first-page":"1326","article-title":"Description of the NCAR Community Atmosphere Model (CAM 3.0)","volume":"226","author":"Collins","year":"2004","journal-title":"NCAR Tech. Note NCAR\/TN-464+STR"},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"192","DOI":"10.1175\/1520-0450(2001)040<0192:DOALSM>2.0.CO;2","article-title":"Development of a land surface model part I: Application in a mesoscale meteorology model","volume":"40","author":"Xiu","year":"2001","journal-title":"J. Appl. Meteor."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"1383","DOI":"10.1175\/JAM2539.1","article-title":"A combined local and non-local closure model for the atmospheric boundary layer. Part 1: Model description and testing","volume":"46","author":"Pleim","year":"2007","journal-title":"J. Appl. Meteor. Clim."},{"key":"ref_60","unstructured":"Ivanov, V., and Dimitrova, R. (2020, January 29\u201330). Sensitivity to the Wrf Model Configuration of the Wind Chill Index for Sofia Region\u2014Preliminary Results. Proceedings of the 1st Internationa Conference on Environmental Protection and Disaster RISKs, Sofia, Bulgaria."},{"key":"ref_61","doi-asserted-by":"crossref","first-page":"189","DOI":"10.1504\/IJEP.2015.074503","article-title":"Numerical study of the atmospheric composition climate of Bulgaria\u2014Validation of the computer simulation results","volume":"57","author":"Gadzhev","year":"2015","journal-title":"Int. J. Environ. Pollut."},{"key":"ref_62","unstructured":"de Leeuw, F., and Mol, W. (2021, June 15). Air Quality and Air Quality Indices: A world apart, 2005, ETC\/ACC Technical Paper 2005\/5. Available online: http:\/\/acm.eionet.europa.eu\/docs\/ETCACC TechnPaper 2005 5 AQ Indices.pdf."},{"key":"ref_63","unstructured":"Georgieva, I. (2014, January 19\u201322). Air Quality Index Evaluations for Bulgaria. Proceedings of the International Conference on Numerical Methods for Scientific Computations and Advanced Applications, Bansko, Bulgaria."},{"key":"ref_64","doi-asserted-by":"crossref","first-page":"402","DOI":"10.1016\/j.camwa.2012.07.002","article-title":"Numerical study of the atmospheric composition in Bulgaria","volume":"65","author":"Gadzhev","year":"2013","journal-title":"Comput. Math. Appl."},{"key":"ref_65","doi-asserted-by":"crossref","first-page":"3317","DOI":"10.1002\/2016JD026267","article-title":"Biospheric and anthropogenic contributors to atmospheric CO2 variability in a residential neighborhood of Phoenix, Arizona","volume":"122","author":"Song","year":"2017","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_66","doi-asserted-by":"crossref","first-page":"47","DOI":"10.1504\/IJEP.2018.099146","article-title":"Contribution of different emission sources to the atmospheric composition formation in the city of Sofia","volume":"64","author":"Gadzhev","year":"2018","journal-title":"Int. J. Environ. Pollut."},{"key":"ref_67","doi-asserted-by":"crossref","first-page":"1066","DOI":"10.1029\/2018EF000891","article-title":"Cooling Effect of Urban Trees on the Built Environment of Contiguous United States","volume":"6","author":"Wang","year":"2018","journal-title":"Earth\u2019s Future"}],"container-title":["Atmosphere"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-4433\/12\/8\/1078\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:49:23Z","timestamp":1760165363000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-4433\/12\/8\/1078"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,8,22]]},"references-count":67,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2021,8]]}},"alternative-id":["atmos12081078"],"URL":"https:\/\/doi.org\/10.3390\/atmos12081078","relation":{"has-preprint":[{"id-type":"doi","id":"10.20944\/preprints202106.0440.v1","asserted-by":"object"}]},"ISSN":["2073-4433"],"issn-type":[{"value":"2073-4433","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,8,22]]}}}