Atmospheric station Křešín u Pacova, Czech Republic – a Central European research infrastructure for studying greenhouse gases, aerosols and air quality
Abstract:Abstract. Long-lasting research infrastructures covering the research areas of atmospheric chemistry, meteorology and climatology are of highest importance. The Atmospheric Station (AS) Křešín u Pacova, central Czech Republic, is focused on monitoring of the occurence and long-range transport of greenhouse gases, atmospheric aerosols, selected gaseous atmospheric pollutants and basic meteorological characteristics. The AS and its 250 m tall tower was built according to the recommendations of the Integrated Car… Show more
“…The closest main road is located approximately 1 km east of the sampling station, and one of the major Czech highways (40,756 cars/day, CSD, 2016 ) is approximately 6 km north and northeast. NAOK is affected by regional and long distance transported air masses, mainly associated with western and southeastern winds ( Dvorská et al, 2015 ; Mbengue et al, 2020 , Mbengue et al, 2018 ; Schwarz et al, 2016 ; Vodička et al, 2015 ; Zíková and Ždímal, 2013 ).…”
Black carbon (BC) is a dominant aerosol light absorber, and its brown carbon (BrC) coating can enhance absorption and lead to uncertainties concerning the radiative forcing estimation. This study investigates the mass absorption cross-section of equivalent BC (MAC
eBC
) during a long-term field measurement (2013–2017) at a rural Central European site. The MAC enhancement factor (E
abs
) and the contribution of BrC coatings to the absorption coefficient (B
abs
) were estimated by combining different approaches. The annual mean B
abs
and MAC
eBC
values decreased slightly over the measurement period associated with change in the submicron aerosol size distribution. Regardless of the wavelength, B
abs
exhibited clear seasonal and diurnal variations, with higher values in winter when a higher absorption Ångström exponent (1.4) was observed due to the local biomass burning (BB). In contrast, MAC
eBC
did not have a distinct temporal trend at 600 nm (7.84 ± 2.79 m
2
g
−1
), while it showed a seasonal trend at 370 nm with higher values in winter (15.64 ± 4.77 m
2
g
−1
). During this season, E
abs_660
was 1.18 ± 0.27 and did not exhibit any clear wavelength dependence, despite the influence of BB. During the study period, BrC-attributed absorption was observed in 31% of the samples, with a contribution of up to 40% of total B
abs
. In summer, the E
abs_660
increased to 1.59 ± 0.60, when a larger BC coating could be formed by secondary aerosol fractions. During this season, MAC
eBC_660
and E
abs_660
showed comparable source profiles that were mainly associated with aged air masses over central Europe, thereby supporting the fact that characteristics of coating materials formed during atmospheric aging are a major factor driving the MAC
eBC_660
measured at the regional background site. Further field investigations of the composition of BC coatings would help to better understand and estimate uncertainties related to the radiative effect of aerosols.
“…The closest main road is located approximately 1 km east of the sampling station, and one of the major Czech highways (40,756 cars/day, CSD, 2016 ) is approximately 6 km north and northeast. NAOK is affected by regional and long distance transported air masses, mainly associated with western and southeastern winds ( Dvorská et al, 2015 ; Mbengue et al, 2020 , Mbengue et al, 2018 ; Schwarz et al, 2016 ; Vodička et al, 2015 ; Zíková and Ždímal, 2013 ).…”
Black carbon (BC) is a dominant aerosol light absorber, and its brown carbon (BrC) coating can enhance absorption and lead to uncertainties concerning the radiative forcing estimation. This study investigates the mass absorption cross-section of equivalent BC (MAC
eBC
) during a long-term field measurement (2013–2017) at a rural Central European site. The MAC enhancement factor (E
abs
) and the contribution of BrC coatings to the absorption coefficient (B
abs
) were estimated by combining different approaches. The annual mean B
abs
and MAC
eBC
values decreased slightly over the measurement period associated with change in the submicron aerosol size distribution. Regardless of the wavelength, B
abs
exhibited clear seasonal and diurnal variations, with higher values in winter when a higher absorption Ångström exponent (1.4) was observed due to the local biomass burning (BB). In contrast, MAC
eBC
did not have a distinct temporal trend at 600 nm (7.84 ± 2.79 m
2
g
−1
), while it showed a seasonal trend at 370 nm with higher values in winter (15.64 ± 4.77 m
2
g
−1
). During this season, E
abs_660
was 1.18 ± 0.27 and did not exhibit any clear wavelength dependence, despite the influence of BB. During the study period, BrC-attributed absorption was observed in 31% of the samples, with a contribution of up to 40% of total B
abs
. In summer, the E
abs_660
increased to 1.59 ± 0.60, when a larger BC coating could be formed by secondary aerosol fractions. During this season, MAC
eBC_660
and E
abs_660
showed comparable source profiles that were mainly associated with aged air masses over central Europe, thereby supporting the fact that characteristics of coating materials formed during atmospheric aging are a major factor driving the MAC
eBC_660
measured at the regional background site. Further field investigations of the composition of BC coatings would help to better understand and estimate uncertainties related to the radiative effect of aerosols.
“…Let us have two data samples of elemental carbon concentration measurements from the atmospheric station Křešín u Pacova, Czech Republic (Dvorská et al, 2015). Each of the samples contains 41 measurements from one week in September (first sample) and October 2013 (second sample).…”
Left-censored data occur frequently in many areas. At present, researchers pay attention to skewed censored distributions more frequently. This paper deals with statistical inference of type I multiply left-censored Weibull and exponential distributions. It suggests a computational procedure for calculation of maximum likelihood estimates of the parameters. The expected Fisher information matrix for estimation of variances of estimated parameters is introduced. The estimates are then used for construction of confidence intervals for the expectation using the maximum likelihood method. Asymptotic tests for comparison of distributions (expectations respectively) of two independent left-censored Weibull samples are proposed. Furthermore, asymptotic tests for assessing suitability of reduction of the Weibull distribution to the exponential distribution are introduced. Finally, the left-censored exponential distribution is briefly described. Methods derived in this paper are illustrated on elemental carbon measurements, and can be applied in analysis of real environmental and/or chemical data.
“…One of the main Czech highways (40,756 cars/day, CSD, 2016 ) is approximately 6 km north and northeast. NAOK is affected by regional and long-distance transported air masses, mainly associated with western and southeastern winds ( Dvorská et al, 2015 ; Mbengue et al, 2018 , Mbengue et al, 2020 , Mbengue et al, 2021 ; Schwarz et al, 2016 ; Vodička et al, 2015 ). Fig.…”
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