Analysis of summertime temperature characteristics and ozone exposure indexes were carried out for eight locations in Poland for a 15year period (1997-2011). The number of days with the maximum temperature exceeding 25 o C and 30 o C was calculated for each year. The analysis covered the 8-hour running average and daily maximum of near surface ozone concentrations. Also, the accumulated exposure when ozone concentrations were above 120 ȝg/m 3 (AOT60) was calculated as a diagnostic indicator of adverse health effects for each year. Although high ozone concentrations are associated with hot temperatures, the exposure to values higher than 120 ȝg /m 3 is correlated with the length of the hot weather period rather than with the occurrence of days with extremely high temperatures. In most cases the elevated ozone concentrations occurred during days when the maximum temperature was higher than 24 o C. Episodes of very high ozone concentrations, exceeding 180 ȝg /m 3 , were not associated with heat wave periods at analysed locations.
Urban heat island (UHI) is one of the most distinctive characteristics of urban climate. The objective of this study is to apply a statistical modeling of the nocturnal atmospheric UHI based on the relationship between observed air temperature from ground stations and remotely sensed temperature of the urban surface. The goal of the approach is to limit input data for the developed modeling method in order to assure transferability of the methodology in different cities. Time series of surface temperature and normalized difference vegetation index are obtained from the MODIS instrument for a 10-year period (2008-2017). The air temperature is collected from the in-situ observational network of 21 stations. The studies are conducted for different locations with gradual changes in urbanization in order to assess the impact of urbanization on the relationship between simultaneous air and surface UHI. The urbanization is described by commonly available land cover metrics. Results showed that the proposed approach provides satisfactory AUHI modeling results for the locations with the least degree of urbanization. The best results are obtained with a simple linear regression model with the iterative procedure to minimize the mean absolute gross error (MAGE). The lowest MAGE for modeled UHI is 1.18°C with 69% of the variance explained. The strongest linear relationship between simultaneous SUHI and AUHI is noted for those station pairs whose surroundings have the highest differences in urbanization, and the highest UHI intensities are observed. The strength of the SUHI/AUHI linear relationship decreases gradually with the increasing urbanization of the stations' surroundings. Index Terms-Air temperature (AT), prediction, regression, statistical modeling, surface temperature, urban climate, urban heat island (UHI).
h i g h l i g h t sComplex studies on aerosol properties during spring on Spitsbergen are presented. In-situ, remote sensing instruments and model results are included in the campaign. Scattering properties were found to be correlated with wind speed. Some sea-spray advections are detected and described in detail. Spring 2014 seems to be relatively clean with only a small load of Arctic Haze events. a r t i c l e i n f o . The subject of this study is to investigate the inesitu, passive and active remote sensing observations as well as numerical simulations to describe the temporal variability of aerosol singleescattering properties during spring season on Spitsbergen. The retrieval of the data indicates several event days with enhanced singleescattering properties due to the existence of sulphate and additional seaesalt load in the atmosphere which is possibly caused by relatively high wind speed. Optical results were confirmed by numerical simulations made by the GEMeAQ model and by chemical observations that indicated up to 45% contribution of the seaesalt to a PM 10 total aerosol mass concentration. An agreement between the in-situ optical and microphysical properties was found, namely: the positive correlation between aerosol scattering coefficient measured by the nephelometer and effective radius obtained from laser aerosol spectrometer as well as negative correlation between aerosol scattering coefficient and the Ångstrom exponent indicated that slightly larger particles dominated during special events. The inesitu surface observations do not show any significant enhancement of the absorption coefficient as well as the black carbon concentration which might occur during spring. All of extensive singleescattering properties indicate a diurnal cycle in Longyearbyen, where 21:00e5:00 data stays at the background level, however increasing during the day by the factor of 3e4. It is considered to be highly connected with local emissions originating in combustion, traffic and harbour activities. On the other hand, no daily fluctuations in NyeÅlesund are observed. Mean values in NyeÅlesund are equal to 8.2, 0.8 Mm À1 and 103 ng/m 3 for scattering, absorption coefficients and black carbon concentration;
Abstract. In the scope of the AQMEII Phase 1 project the GEM-AQ model was run over Europe for the year 2006. The modelling domain was defined using a global variable resolution grid with a rotated equator and uniform resolution of 0.2• over the European continent. Spatial distribution and temporal variability of the GEM-AQ model results were analysed for surface ozone and PM 10 concentrations. Model results were compared with measurements available in the ENSEMBLE database. Statistical measures were used to evaluate performance of the GEM-AQ model. The mean bias error, the mean absolute gross error and the Pearson correlation coefficient were calculated for the maximum 8 h running average ozone concentrations and daily mean PM 10 concentrations. The GEM-AQ model performance was characterized for station types, European climatic regions and seasons. The best performance for ozone was obtained at suburban stations, and the worst performance was obtained for rural stations where the model tends to underestimate. The best results for PM 10 were calculated for urban stations, while over most of Europe concentrations at rural sites were too high. Discrepancies between modelled and observed concentrations were discussed in the context of emission data uncertainty as well as the impact of large-scale dynamics and circulation of air masses. Presented analyses suggest that interpretation of modelling results is enhanced when regional climate characteristics are taken into consideration.
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