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15. Two regimes in the regularity of sunspot numberAlexander Shapoval, Jean-Louis Le Mouël, Vincent Courtillot, M. Shnirman, 2013, original scientific article Abstract: Sunspot numbers WN display quasi-periodical variations that undergo regime changes. These irregularities could indicate a chaotic system and be measured by Lyapunov exponents. We define a functional λ (an "irregularity index") that is close to the (maximal) Lyapunov exponent for dynamical systems and well defined for series with a random component: this allows one to work with sunspot numbers. We compute λ for the daily WN from 1850 to 2012 within 4 yr sliding windows: λ exhibit sharp maxima at solar minima and secondary maxima at solar maxima. This pattern is reflected in the ratio R of the amplitudes of the main versus secondary peaks. Two regimes have alternated in the past 150 yr, R1 from 1850 to 1915 (large λ and R values) and R2 from 1935 to 2005 (shrinking difference between main and secondary maxima, R values between 1 and 2). We build an autoregressive model consisting of Poisson noise plus an 11 yr cycle and compute its irregularity index. The transition from R1 to R2 can be reproduced by strengthening the autocorrelation a of the model series. The features of the two regimes are stable for model and WN with respect to embedding dimension and delay. Near the time of the last solar minimum (~2008), the irregularity index exhibits a peak similar to the peaks observed before 1915. This might signal a regime change back from R2 to R1 and the onset of a significant decrease of solar activity.
Keywords: Lyapunov exponent, solar activity, solar cycle
Published in RUNG: 19.04.2021; Views: 1848; Downloads: 59
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16. Dynamics of sunspot series on time scales from days to years : correlation of sunspot births, variable lifetimes, and evolution of the high-frequency spectral componentAlexander Shapoval, Jean-Louis Le Mouël, M. Shnirman, Vincent Courtillot, 2017, original scientific article Keywords: sunspots series, average lifetime, average birthrate, data analysis
Published in RUNG: 30.03.2021; Views: 2039; Downloads: 103
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18. Influence of very large spatial heterogeneity on estimates of sea-level trendsAlexander Shapoval, Jean-Louis Le Mouël, Vincent Courtillot, M. Shnirman, 2020, original scientific article Abstract: We propose a new method to estimate sub-decadal to centennial time scales of sea-level change. Since the coastal data exhibit large spatial heterogeneity and temporal variability, the global sea-level rate is estimated as an appropriate average of the rates observed at available locations and computed with sliding windows. We claim that under such heterogeneity the median serves as a better representative of an adequate average than the mean. With this approach, the sea-level rate in 60 to 70 yr windows over the past century is found to be smaller than 1.7-1.9 mm/yr. These upper estimates are in line with those obtained with a scarce list of available long quasi-gapless series
Keywords: sea-level rise, median, sliding window, statistically significant trend
Published in RUNG: 16.03.2021; Views: 1892; Downloads: 0
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19. The new instrument using a TC–BC (total carbon–black carbon) method for the online measurement of carbonaceous aerosolsMartin Rigler, Luka Drinovec, Gašper Lavrič, Anastasia Vlachou, André S. H. Prévôt, Jean-Luc Jaffrezo, IASONAS STAVROULAS, Jean Sciare, Judita Burger, Irena Krajnc, Janja Turšič, Anthony D. A. Hansen, Griša Močnik, 2020, original scientific article Abstract: We present a newly developed total carbon analyzer (TCA08) and a method for online speciation of carbonaceous aerosol with a high time resolution. The total carbon content is determined by flash heating of a sample collected on a quartz-fiber filter with a time base between 20 min and 24 h. The limit of detection is approximately 0.3 µg C, which corresponds to a concentration of 0.3 µg C m−3 at a sample flow rate of 16.7 L min−1 and a 1 h sampling time base. The concentration of particulate equivalent organic carbon (OC) is determined by subtracting black carbon concentration, concurrently measured optically by an Aethalometer®, from the total carbon concentration measured by the TCA08. The combination of the TCA08 and Aethalometer (AE33) is an easy-to-deploy and low-maintenance continuous measurement technique for the high-time-resolution determination of equivalent organic and elemental carbon (EC) in different particulate matter size fractions, which avoids pyrolytic correction and the need for high-purity compressed gases. The performance of this online method relative to the standardized off-line thermo-optical OC–EC method and respective instruments was evaluated during a winter field campaign at an urban background location in Ljubljana, Slovenia. The organic-matter-to-organic-carbon ratio obtained from the comparison with an aerosol chemical speciation monitor (ACSM) was OM/OC=1.8, in the expected range.
Keywords: total carbon, aeroosl, black carbon, carbonaceous matter
Published in RUNG: 17.08.2020; Views: 2931; Downloads: 76
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20. A new optical-based technique for real-time measurements of mineral dust concentration in PM10 using a virtual impactorLuka Drinovec, Jean Sciare, IASONAS STAVROULAS, Spiros Bezantakos, Michael Pikridas, FLORIN UNGA, Chrysanthos Savvides, Bojana Višnjić, Maja Remškar, Griša Močnik, 2020, original scientific article Abstract: Atmospheric mineral dust influences Earth’s radiative
budget, cloud formation, and lifetime; has adverse
health effects; and affects air quality through the increase of
regulatory PM10 concentrations, making its real-time quantification
in the atmosphere of strategic importance. Only
few near-real-time techniques can discriminate dust aerosol
in PM10 samples and they are based on the dust chemical
composition. The online determination of mineral dust using
aerosol absorption photometers offers an interesting and
competitive alternative but remains a difficult task to achieve.
This is particularly challenging when dust is mixed with
black carbon, which features a much higher mass absorption
cross section. We build on previous work using filter photometers
and present here for the first time a highly timeresolved
online technique for quantification of mineral dust
concentration by coupling a high-flow virtual impactor (VI)
sampler that concentrates coarse particles with an aerosol absorption
photometer (Aethalometer, model AE33). The absorption
of concentrated dust particles is obtained by subtracting
the absorption of the submicron (PM1) aerosol fraction
from the absorption of the virtual impactor sample (VIPM1
method). This real-time method for detecting desert
dust was tested in the field for a period of 2 months (April and
May 2016) at a regional background site of Cyprus, in the
Eastern Mediterranean. Several intense desert mineral dust
events were observed during the field campaign with dust
concentration in PM10 up to 45 μgm
Keywords: aerosol absorption, mineral dust, on-line detection, air quality
Published in RUNG: 20.07.2020; Views: 2768; Downloads: 0
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