TY  - JOUR
AU  - Ajtić, Jelena
AU  - Brattich, Erika
AU  - Sarvan, Darko
AU  - Đurđević, V.
AU  - Hernández-Ceballos, Miguel A.
PY  - 2018
UR  - https://vet-erinar.vet.bg.ac.rs/handle/123456789/1649
AB  - Relationships between the beryllium-7 activity concentrations in surface air and meteorological parameters (temperature, atmospheric pressure, and precipitation), teleconnection indices (Arctic Oscillation, North Atlantic Oscillation, and Scandinavian pattern) and number of sunspots are investigated using two multivariate statistical techniques: hierarchical cluster and factor analysis. The beryllium-7 surface measurements over 1995-2011, at four sampling sites located in the Scandinavian Peninsula, are obtained from the Radioactivity Environmental Monitoring Database. In all sites, the statistical analyses show that the beryllium-7 concentrations are strongly linked to temperature. Although the beryllium-7 surface concentration exhibits the well-characterised spring/summer maximum, our study shows that extremely high beryllium-7 concentrations, defined as the values exceeding the 90th percentile in the data records for each site, also occur over the October-March period. Two types of autumn/winter extremes are distinguished: type-1 when the number of extremes in a given month is less than three, and type-2 when at least three extremes occur in a month. Factor analysis performed for these autumn/winter events shows a weaker effect of temperature and a stronger impact of the transport and production signal on the beryllium-7 concentrations. Further, the majority of the type-2 extremes are associated with a very high monthly Scandinavian teleconnection index. The type-2 extremes that occurred in January, February and March are also linked to sudden stratospheric warmings of the Arctic vortex. Our results indicate that the Scandinavian teleconnection index might be a good indicator of the meteorological conditions facilitating extremely high beryllium-7 surface concentrations over Scandinavia during autumn and winter.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Chemosphere
T1  - Factors affecting the Be-7 surface concentration and its extremely high occurrences over the Scandinavian Peninsula during autumn and winter
VL  - 199
SP  - 278
EP  - 285
DO  - 10.1016/j.chemosphere.2018.02.052
ER  - 

@article{
author = "Ajtić, Jelena and Brattich, Erika and Sarvan, Darko and Đurđević, V. and Hernández-Ceballos, Miguel A.",
year = "2018",
abstract = "Relationships between the beryllium-7 activity concentrations in surface air and meteorological parameters (temperature, atmospheric pressure, and precipitation), teleconnection indices (Arctic Oscillation, North Atlantic Oscillation, and Scandinavian pattern) and number of sunspots are investigated using two multivariate statistical techniques: hierarchical cluster and factor analysis. The beryllium-7 surface measurements over 1995-2011, at four sampling sites located in the Scandinavian Peninsula, are obtained from the Radioactivity Environmental Monitoring Database. In all sites, the statistical analyses show that the beryllium-7 concentrations are strongly linked to temperature. Although the beryllium-7 surface concentration exhibits the well-characterised spring/summer maximum, our study shows that extremely high beryllium-7 concentrations, defined as the values exceeding the 90th percentile in the data records for each site, also occur over the October-March period. Two types of autumn/winter extremes are distinguished: type-1 when the number of extremes in a given month is less than three, and type-2 when at least three extremes occur in a month. Factor analysis performed for these autumn/winter events shows a weaker effect of temperature and a stronger impact of the transport and production signal on the beryllium-7 concentrations. Further, the majority of the type-2 extremes are associated with a very high monthly Scandinavian teleconnection index. The type-2 extremes that occurred in January, February and March are also linked to sudden stratospheric warmings of the Arctic vortex. Our results indicate that the Scandinavian teleconnection index might be a good indicator of the meteorological conditions facilitating extremely high beryllium-7 surface concentrations over Scandinavia during autumn and winter.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Chemosphere",
title = "Factors affecting the Be-7 surface concentration and its extremely high occurrences over the Scandinavian Peninsula during autumn and winter",
volume = "199",
pages = "278-285",
doi = "10.1016/j.chemosphere.2018.02.052"
}

Ajtić, J., Brattich, E., Sarvan, D., Đurđević, V.,& Hernández-Ceballos, M. A.. (2018). Factors affecting the Be-7 surface concentration and its extremely high occurrences over the Scandinavian Peninsula during autumn and winter. in Chemosphere
Pergamon-Elsevier Science Ltd, Oxford., 199, 278-285.
https://doi.org/10.1016/j.chemosphere.2018.02.052

Ajtić J, Brattich E, Sarvan D, Đurđević V, Hernández-Ceballos MA. Factors affecting the Be-7 surface concentration and its extremely high occurrences over the Scandinavian Peninsula during autumn and winter. in Chemosphere. 2018;199:278-285.
doi:10.1016/j.chemosphere.2018.02.052 .

Ajtić, Jelena, Brattich, Erika, Sarvan, Darko, Đurđević, V., Hernández-Ceballos, Miguel A., "Factors affecting the Be-7 surface concentration and its extremely high occurrences over the Scandinavian Peninsula during autumn and winter" in Chemosphere, 199 (2018):278-285,
https://doi.org/10.1016/j.chemosphere.2018.02.052 . .

TY  - JOUR
AU  - Sarvan, Darko
AU  - Stratimirović, Đorđe
AU  - Blesić, Suzana
AU  - Đurđević, V.
AU  - Miljković, V.
AU  - Ajtić, Jelena
PY  - 2017
UR  - https://vet-erinar.vet.bg.ac.rs/handle/123456789/1497
AB  - The dynamics of the beryllium-7 specific activity in surface air over 1987-2011 is analyzed using wavelet transform (WT) analysis and time -dependent detrended moving average (tdDMA) method, WT analysis gives four periodicities in the beryllium-7 specific activity: one month, three months, one year, and three years. These intervals are further used in tdDMA to calculate local autocorrelation exponents for precipitation, tropopause height and teleconnection indices. Our results show that these parameters share common periods with the beryllium-7 surface concentration. tdDMA method indicates that on the characteristic intervals of one year and shorter, the beryllium-7 specific activity is strongly autocorrelated. On the three-year interval, the beryllium-7 specific activity shows periods of anticorrelat ion, implying slow changes in its dynamics that become evident only over a prolonged period of time. A comparison of the Hurst exponents of all the variables on the one- and three-year intervals suggest some similarities in their dynamics. Overall, a good agreement in the behavior of the teleconnection indices and specific activity of beryllium-7 in surface air is noted.
PB  - Elsevier, Amsterdam
T2  - Physica A-Statistical Mechanics and Its Applications
T1  - Dynamics of beryllium-7 specific activity in relation to meteorological variables, tropopause height, teleconnection indices and sunspot number
VL  - 469
SP  - 813
EP  - 823
DO  - 10.1016/j.physa.2016.11.040
ER  - 

@article{
author = "Sarvan, Darko and Stratimirović, Đorđe and Blesić, Suzana and Đurđević, V. and Miljković, V. and Ajtić, Jelena",
year = "2017",
abstract = "The dynamics of the beryllium-7 specific activity in surface air over 1987-2011 is analyzed using wavelet transform (WT) analysis and time -dependent detrended moving average (tdDMA) method, WT analysis gives four periodicities in the beryllium-7 specific activity: one month, three months, one year, and three years. These intervals are further used in tdDMA to calculate local autocorrelation exponents for precipitation, tropopause height and teleconnection indices. Our results show that these parameters share common periods with the beryllium-7 surface concentration. tdDMA method indicates that on the characteristic intervals of one year and shorter, the beryllium-7 specific activity is strongly autocorrelated. On the three-year interval, the beryllium-7 specific activity shows periods of anticorrelat ion, implying slow changes in its dynamics that become evident only over a prolonged period of time. A comparison of the Hurst exponents of all the variables on the one- and three-year intervals suggest some similarities in their dynamics. Overall, a good agreement in the behavior of the teleconnection indices and specific activity of beryllium-7 in surface air is noted.",
publisher = "Elsevier, Amsterdam",
journal = "Physica A-Statistical Mechanics and Its Applications",
title = "Dynamics of beryllium-7 specific activity in relation to meteorological variables, tropopause height, teleconnection indices and sunspot number",
volume = "469",
pages = "813-823",
doi = "10.1016/j.physa.2016.11.040"
}

Sarvan, D., Stratimirović, Đ., Blesić, S., Đurđević, V., Miljković, V.,& Ajtić, J.. (2017). Dynamics of beryllium-7 specific activity in relation to meteorological variables, tropopause height, teleconnection indices and sunspot number. in Physica A-Statistical Mechanics and Its Applications
Elsevier, Amsterdam., 469, 813-823.
https://doi.org/10.1016/j.physa.2016.11.040

Sarvan D, Stratimirović Đ, Blesić S, Đurđević V, Miljković V, Ajtić J. Dynamics of beryllium-7 specific activity in relation to meteorological variables, tropopause height, teleconnection indices and sunspot number. in Physica A-Statistical Mechanics and Its Applications. 2017;469:813-823.
doi:10.1016/j.physa.2016.11.040 .

Sarvan, Darko, Stratimirović, Đorđe, Blesić, Suzana, Đurđević, V., Miljković, V., Ajtić, Jelena, "Dynamics of beryllium-7 specific activity in relation to meteorological variables, tropopause height, teleconnection indices and sunspot number" in Physica A-Statistical Mechanics and Its Applications, 469 (2017):813-823,
https://doi.org/10.1016/j.physa.2016.11.040 . .

TY  - CONF
AU  - Maletić, Dimitrije
AU  - Ajtić, Jelena
AU  - Đurđević, V.
AU  - Todorović, Dragana
AU  - Nikolić, J.
AU  - Banjanac, R.
AU  - Udovičić, V.
PY  - 2014
UR  - https://vet-erinar.vet.bg.ac.rs/handle/123456789/1149
AB  - Activities of lead-210 and beryllium-7 have been monitored at the Vinča Institute of Nuclear Sciences in Belgrade, Serbia. The monthly mean activities in composite aerosol samples were determined on HPGe detectors by standard gamma spectrometry. The meteorological data, consisting of the temperature, atmospheric pressure, relative humidity, sunshine hours and cloud cover data were obtained from the European Climate Assessment & Dataset and the Republic Hydrometeorological Service of Serbia. Five teleconnection indices of large scale atmospheric circulation: North Atlantic Oscillation, East Atlantic Pattern, East Atlantic/West Russia Pattern, Scandinavia Pattern, and Polar/Eurasia Pattern were obtained from the data archive of the United States National Oceanic and Atmospheric Administration's Climate Prediction Center. The first lead-210 and beryllium-7 activities measured at the Vinča Institute date back to 1985 and 1991, respectively, and their relation with the climate variables and teleconnection indices is investigated using multivariate methods of analysis. The most appropriate multivariate method of analysis of these sets of measurements is selected from a wide spectrum of multivariate methods developed for data analysis in high-energy physics and implemented in the Toolkit for Multivariate Analysis software package. The evaluation ranking results based on the best signal efficiency and purity, show that the Boosted Decision Trees (BDT) multivariate method is the most suitable for the variable analysis. Further multivariate analysis results give insight into the dependence of lead-210 and beryllium-7 concentrations upon the climate variables and atmospheric circulation (via the teleconnection indices) during the time of measurements. The BDT method singles out the Scandinavia Pattern index as the variable with the highest importance for both radionuclides. Amongst the climate variables, temperature shows the strongest influence on the radionuclide concentrations, while relative humidity is the lowest ranking variable. Moreover, the multivariate regression methods give a good approximation of lead-210 and beryllium-7 concentrations for all the sets of climate variables and teleconnection indices.
PB  - RAD Association
C3  - RAD Conference Proceedings
T1  - Multivariate analysis of climate variables, teleconnection indices and activities of lead-210 and beryllium-7 in surface air in Belgrade, Serbia
SP  - 13
EP  - 16
UR  - https://hdl.handle.net/21.15107/rcub_veterinar_1149
ER  - 

@conference{
author = "Maletić, Dimitrije and Ajtić, Jelena and Đurđević, V. and Todorović, Dragana and Nikolić, J. and Banjanac, R. and Udovičić, V.",
year = "2014",
abstract = "Activities of lead-210 and beryllium-7 have been monitored at the Vinča Institute of Nuclear Sciences in Belgrade, Serbia. The monthly mean activities in composite aerosol samples were determined on HPGe detectors by standard gamma spectrometry. The meteorological data, consisting of the temperature, atmospheric pressure, relative humidity, sunshine hours and cloud cover data were obtained from the European Climate Assessment & Dataset and the Republic Hydrometeorological Service of Serbia. Five teleconnection indices of large scale atmospheric circulation: North Atlantic Oscillation, East Atlantic Pattern, East Atlantic/West Russia Pattern, Scandinavia Pattern, and Polar/Eurasia Pattern were obtained from the data archive of the United States National Oceanic and Atmospheric Administration's Climate Prediction Center. The first lead-210 and beryllium-7 activities measured at the Vinča Institute date back to 1985 and 1991, respectively, and their relation with the climate variables and teleconnection indices is investigated using multivariate methods of analysis. The most appropriate multivariate method of analysis of these sets of measurements is selected from a wide spectrum of multivariate methods developed for data analysis in high-energy physics and implemented in the Toolkit for Multivariate Analysis software package. The evaluation ranking results based on the best signal efficiency and purity, show that the Boosted Decision Trees (BDT) multivariate method is the most suitable for the variable analysis. Further multivariate analysis results give insight into the dependence of lead-210 and beryllium-7 concentrations upon the climate variables and atmospheric circulation (via the teleconnection indices) during the time of measurements. The BDT method singles out the Scandinavia Pattern index as the variable with the highest importance for both radionuclides. Amongst the climate variables, temperature shows the strongest influence on the radionuclide concentrations, while relative humidity is the lowest ranking variable. Moreover, the multivariate regression methods give a good approximation of lead-210 and beryllium-7 concentrations for all the sets of climate variables and teleconnection indices.",
publisher = "RAD Association",
journal = "RAD Conference Proceedings",
title = "Multivariate analysis of climate variables, teleconnection indices and activities of lead-210 and beryllium-7 in surface air in Belgrade, Serbia",
pages = "13-16",
url = "https://hdl.handle.net/21.15107/rcub_veterinar_1149"
}

Maletić, D., Ajtić, J., Đurđević, V., Todorović, D., Nikolić, J., Banjanac, R.,& Udovičić, V.. (2014). Multivariate analysis of climate variables, teleconnection indices and activities of lead-210 and beryllium-7 in surface air in Belgrade, Serbia. in RAD Conference Proceedings
RAD Association., 13-16.
https://hdl.handle.net/21.15107/rcub_veterinar_1149

Maletić D, Ajtić J, Đurđević V, Todorović D, Nikolić J, Banjanac R, Udovičić V. Multivariate analysis of climate variables, teleconnection indices and activities of lead-210 and beryllium-7 in surface air in Belgrade, Serbia. in RAD Conference Proceedings. 2014;:13-16.
https://hdl.handle.net/21.15107/rcub_veterinar_1149 .

Maletić, Dimitrije, Ajtić, Jelena, Đurđević, V., Todorović, Dragana, Nikolić, J., Banjanac, R., Udovičić, V., "Multivariate analysis of climate variables, teleconnection indices and activities of lead-210 and beryllium-7 in surface air in Belgrade, Serbia" in RAD Conference Proceedings (2014):13-16,
https://hdl.handle.net/21.15107/rcub_veterinar_1149 .

TY  - CONF
AU  - Ajtić, Jelena
AU  - Stratimirović, Đorđe
AU  - Đurđević, V.
AU  - Todorović, Dragana
AU  - Nikolić, J.
PY  - 2014
UR  - https://vet-erinar.vet.bg.ac.rs/handle/123456789/1130
AB  - Activities of beryllium-7 and lead-210 are monitored in ground level air in Belgrade, Serbia. The measuring sites are located at the Institute of Nuclear Sciences Vinča. The activities are determined on HPGe detectors by standard gamma spectrometry. Five teleconnection indices of large scale atmospheric circulation: North Atlantic Oscillation, East Atlantic Pattern, East Atlantic/West Russia Pattern, Scandinavia Pattern, and Polar/Eurasia Pattern are obtained from the data archive of the United States National Oceanic and Atmospheric Administration's Climate Prediction Center. The collected time series consist of monthly values and span more than two decades: beryllium-7 since 1991, lead-210 since 1985, and the teleconnection indices since 1950, thus offering data arrays of sufficient lengths for wavelet spectral analysis. A relation between the radionuclides' activities and the indices is first investigated using Pearson's correlation coefficients. The computed coefficients do not indicate a linear relationship between the variables. However, the wavelet spectral analysis shows a number of common characteristic frequencies in the data arrays. The annual cycle of all the variables is clearly evident. A common time period of two to three years is also found, as well as a higher frequency variability corresponding to five to six months.
PB  - RAD Association
C3  - RAD Conference Proceedings
T1  - Wavelet spectral analysis of teleconnection indices and activities of beryllium-7 and lead-210 in ground level air in Belgrade, Serbia
SP  - 53
EP  - 56
UR  - https://hdl.handle.net/21.15107/rcub_veterinar_1130
ER  - 

@conference{
author = "Ajtić, Jelena and Stratimirović, Đorđe and Đurđević, V. and Todorović, Dragana and Nikolić, J.",
year = "2014",
abstract = "Activities of beryllium-7 and lead-210 are monitored in ground level air in Belgrade, Serbia. The measuring sites are located at the Institute of Nuclear Sciences Vinča. The activities are determined on HPGe detectors by standard gamma spectrometry. Five teleconnection indices of large scale atmospheric circulation: North Atlantic Oscillation, East Atlantic Pattern, East Atlantic/West Russia Pattern, Scandinavia Pattern, and Polar/Eurasia Pattern are obtained from the data archive of the United States National Oceanic and Atmospheric Administration's Climate Prediction Center. The collected time series consist of monthly values and span more than two decades: beryllium-7 since 1991, lead-210 since 1985, and the teleconnection indices since 1950, thus offering data arrays of sufficient lengths for wavelet spectral analysis. A relation between the radionuclides' activities and the indices is first investigated using Pearson's correlation coefficients. The computed coefficients do not indicate a linear relationship between the variables. However, the wavelet spectral analysis shows a number of common characteristic frequencies in the data arrays. The annual cycle of all the variables is clearly evident. A common time period of two to three years is also found, as well as a higher frequency variability corresponding to five to six months.",
publisher = "RAD Association",
journal = "RAD Conference Proceedings",
title = "Wavelet spectral analysis of teleconnection indices and activities of beryllium-7 and lead-210 in ground level air in Belgrade, Serbia",
pages = "53-56",
url = "https://hdl.handle.net/21.15107/rcub_veterinar_1130"
}

Ajtić, J., Stratimirović, Đ., Đurđević, V., Todorović, D.,& Nikolić, J.. (2014). Wavelet spectral analysis of teleconnection indices and activities of beryllium-7 and lead-210 in ground level air in Belgrade, Serbia. in RAD Conference Proceedings
RAD Association., 53-56.
https://hdl.handle.net/21.15107/rcub_veterinar_1130

Ajtić J, Stratimirović Đ, Đurđević V, Todorović D, Nikolić J. Wavelet spectral analysis of teleconnection indices and activities of beryllium-7 and lead-210 in ground level air in Belgrade, Serbia. in RAD Conference Proceedings. 2014;:53-56.
https://hdl.handle.net/21.15107/rcub_veterinar_1130 .

Ajtić, Jelena, Stratimirović, Đorđe, Đurđević, V., Todorović, Dragana, Nikolić, J., "Wavelet spectral analysis of teleconnection indices and activities of beryllium-7 and lead-210 in ground level air in Belgrade, Serbia" in RAD Conference Proceedings (2014):53-56,
https://hdl.handle.net/21.15107/rcub_veterinar_1130 .