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A CORRELATION STUDY BETWEEN OZONE AND VOLCANIC ACTIVITY

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A cross-correlation study for time-lags of -t-5 yrs between eleven ground based ozone stations (1957-1985) for ~ = 40°N-75 ° N and ), = 30 o E-114 ° W and five volcanic emissivity indices has shown their close connection: significant correlations
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  A CORRELATION STUDY BETWEEN OZONE AND VOLCANIC ACTIVITY I. LIRITZIS 1 C. POULAKOS 1, E. LAGIOS 2 and D. KOSMATOS 2 1Research Center for Astronomy and Applied Mathematics, Academy of Athens, 14 Anagnostopoulou str., Athens 106 73, Greece; 2Department of Geothermy and Geophysics, University of Athens, Panepistimiopolis, lllisia, Athens 157 84, Greece (Received 15 September 1994) Abstract. A cross-correlation study for time-lags of -t-5 yrs between eleven ground based ozone stations (1957-1985) for ~ = 40°N-75 ° N and ), = 30 o E-114 ° W and five volcanic emissivity indices has shown their close connection: significant correlations well above 90% were obtained. Intepretation of these positive/negative correlations (r) was based on the global wind circulation (aided also by a 2-D, 3-D representation between ~p, A, r), and the types of volcanic aerosols leading to heterogeneous chemical reactions with ozone. Key words: ozone, volcanic eruption, cross-correlation 1. Introduction The recent concern of the world scientific community about the ozone depletion layer in the atmosphere, especially above the Antarctic - the so called Ozone Hole - has focus research on the anthropogenic effects on ozone. The industrial CFC's is considered as the main agent for such an ozone deficiency, albeit it has been shown that volcanic aerosols, after major volcanic eruptions or via gas release from fumaroles, is another ozone destruction cause. However, a detailed spectrum analysis of ozone data (1957-1992) by Xanthakis et al. (1993), has forwarded the idea that causes of ozone layer variations obeys to mainly physical mechanisms. Therefore, the ozone layer varies (and it may have been varied so in the past) in a quasi-periodic manner, whereas, several quasi-periodic terms are superimposed upon each other forming a network of such periodic components. Global volcanicity is here considered as a physical agent which may well influ- ence the ozone layer. In fact, the emitted tephra and gases which accompanied large volcanic eruptions, that reach the height of at least 30 kin, react chemically with ozone (03). Otherwise, evidence for stratospheric ozone-depleting heterogeneous chemistry on volcanic aerosols from volcanoes, such as the Et Chichon and Mt. Pinatubo, has been quoted (Arnold et al. 1990; Pitari and Rizi, 1993). Moreover, the effect of explosive volcanic eruptions on other atmospheric parameters in ozone heights (30-40 km) has been examined, e.g. for solar transmit- tance variation. Indeed, prior to the Agung 1963 event, where absence of significant aerosol-producing eruptions is observed, the apparent solar transmittance follows a biennial oscillation; whereas after 1963 to 1970, the solar transmittance is decreased by 1.5% and recovers to pre-Agung levels in 1970 (Sigurdsson, 1989). Earth, Moon and Planets 66: 217-230, 1994. ~) 1994 Kluwer Academic Publishers. Printed in the Netherlands.  218 L LIRITZIS ET AL. The effect of volcanic emission on ozone variations is examined applying cross- correlation studies between eleven ground-based ozone stations (~ = 40 ° N-75 ° N and A = 30 ° E-114 ° W) and four different volcanic indices, namely; number of volcanoes with volcanic emissivity index (VEI) 2, 3, the total number of volcanoes (VEI = 1 to 5 inclusive) and the total amount of volcanic tephra (in m3). The tephra index is chosen as an indirect index of total released gases from global volcanic eruptions, assuming a linear relationship between the two. Although VEI > 4 are most penetrating to ozone heights, VEI 2 and 3, surely, reach ozone layers by atmospheric circulation. We bear, however, in mind that large VEI's do not necessarily always imply high levels of SO2 or other chemical agents. Nevertheless, an exact and complete physical mechanism of volcanic output interaction with ozone is not fully understood. Therefore, the present investigation aims at such a target. 2. Data The ozone data set were supplied by the NASA/WMO for the WMO assessment on the ozone layer (WMO, Reports, No 18 (1988) and 25 (1991)) and refers to eleven stations. The ozone layer for all these stations varies between a minimum of 240 Dobson Units (D.U.) and a maximum of 560 D.U. The data cover a period of 23-28 years (1957-1985). In some stations there were missing data for upto three years (10% of total record) which were replaced by the average of the total record of each station. The VEI data (as annual frequency of occurrence numbers) were taken from the catalogue of Simkin et al. (1981) and McCle land et al. (1989). The volcanoes with VEI = 1 were of very low power and VEI = 4 and 5 were a few to treat them with a sound statistical basis. 3. The Cross-Correlation Analysis Linear cross-correlation analysis of the two variables was performed, for time-lags t = -t-5 years. Prior to this a 3rd degree polynomial was detrended from all data series (subtraction of their trend). Tables I-IV present the correlation coefficients with the associated probabilities (higher than 50%) of the four variable pairs and Figures 1 (a-f) show some characteristic illustrations for these variations. 3.1. VEI 2 - OZONE The highest (r) with the higher significance occurs mainly for time lag +2 years (rmax = 0.39, t = -2, 96% for Edmonton), though there are some cases of high (r) for t = 3-4 years and for t = 0. This variable (r) depends upon the station's location and the particular periodic nature of each ozone data set (Table I). However, the correlation coefficient seems to exhibit a cyclic variation for the time lags of t = 4-5 years. (Figure lb). This is expected when the quasi-  A CORRELATION STUDY BETWEEN OZONE AND VOLCANIC ACTIVITY 219 TABLE I Linear-correlation coefficient (r) between Ozone and VEI 2 and corresponding probability of exceeding (r) in a random sample of observations taken from an uncorrelated parent population (significances S > 50% in parenthesis, in blanks S < 50%). Ozone stations (n) -5 -4 -3 -2 -1 0 1 2 3 4 5 n = number of data Arosa (28) = 460 46 r )~ = 090 40' E Bismarck (25) = 460 46 r )~ = 100 ° 45 r W Caribou (23) ~p = 460 52 ~ ), = 68 ° 01 ~ W Edmonton (28) = 530 3# )~= 113° 31tW Goosebay (23) = 530 20 r )~ = 600 25' W Hradec Kr~il6ve (23) = 500 11' )~ = 150 50' E Lerwick (28) = 60 ° 08' )~=01 ° ll'W Rome (28) = 410 54' ,~ = 12 o 29'E Resolute (27) = 740 43' ,~ = 94 ° 59' W Reykj avik (24) = 640 08' )~ = 21 o 54'W Toronto (25) = 43 ° 40' )~ = 79 ° 24' W -0.06 -0.02 0.37 -0.08 0.13 0.008 0.08 0.16 -0.03 0.17 (92%) (50%) (65%) (65%) -0.05 -0.09 -0.10 -0.02 -0.20 0.07 0.07 0.04 -0.18 0.09 0.0009 0.07 (75%) (65%) -0.12 0.17 -0.21 -0.25 0.01 0.09 0.006 -0.19 0.01 0.02 0.18 (55%) (60%) (70%) (55%) (55%) 0.03 -0.13 -0.09 -0.39 0.05 0.05 -0.02 -0.08 0.04 0.ll 0.21 (96%) (60%) -0.14 0.28 --0.01 -0.18 0.023 -0.15 0.04 -0.22 --0.10 0.004 0.20 (70%) (55%) (50%) (65%) (60%) 0.019 0.08 -0.24 0.03 0.16 0.19 (70%) (50%) (65%) -0.11 -0.09 -0.13 -0.07 -0.11 0.10 0.13 0.13 0.16 0.02 0.004 -0.26 -0.003 -0.24 -0.06 -0.29 (55%) (80%) (78%) (85%) 0.04 -0.04 -0.06 -0.22 -0.10 -0.11 0.09 -0.20 0.06 0.13 0.19 (70%) (65%) (60%) 0.07 0.32 -0.10 -0.23 --0.08 0.29 0.17 -0.007 0.14 -0. ll 0.18 (85%) (70%) (85%) (60%) (50%) (60%) -0.02 0.004 -0.11 -0.19 -0.12 0.014 -0.006 -0.21 0.14 0.07 0.26 (60 ) (75%) (75%) -0.13 -0.04 0.24 -0.09 0.09 -0.16 -0.12 --0.20 -0.12 -0.28 (70%) (60%) (65%) (78%) 0.001 periodic variations of both ozone (e.g., 3, 4, 6 years and the quasibiennial oscillation (QBO), Xanthakis et al. 1993) and volcanoes (2-25 years, Liritzis et al. 1994) is considered.  220 i. LIRITZIS ET AL. TABLE II Correlation coefficient (r) between Ozone and volcanic tephra and corresponding probability of exceeding (r) in a random sample of observations taken from an uncorrelated parent population (significances S > 50% in parenthesis, in blanks S < 50%). Ozone stations (n) -5 -4 -3 -2 -1 0 1 2 3 4 5 n = number of data Arosa (28) = 46 ° 46'E -0.09 -0.19 -0.19 -0.09 -0.25 0.16 0.18 0.06 0.16 0.06 -0.04 )~ = 09 ° 40' E (60%) (60%) (80%) (70%) (70%) (60%) Bismarck (25) = 460 46' 0.29 -0.39 0.023 0.037 -0.16 0.08 0.05 0.29 -0.14 0.12 -0.10 A = 100 ° 45 r W (80%) (93%) (55%) (85%) Caribou (23) = 46 ° 52' -0.05 -0.23 0.17 0.09 -0.15 0.19 0.13 0.01 -0.20 0.04 0.06 ), = 68 ° 01' W (55%) (52%) (59%) (60%) (65%) Edmonton (28) = 53 o 34' 0.02 -0.30 -0.11 -0.16 0.09 0.37 -0.10 0.20 -0.10 0.02 -0.26 = 113 o 31' W (85%) (58%) (95%) (70%) (75%) Goosebay (23) ~p = 530 20' -0.12 -0.10 0.22 0.42 -0.27 0.06 0.01 0.05 -0.33 0.034 0.19 * = 60 o 25' W (65%) (95%) (75%) (85%) (55%) Hradec Kr~il6ve (23) = 500 11' -0.12 -0.08 0.11 0.002 -0.11 0.34 -0.01 0.01 -0.19 0.15 0.035 = 15 o 50' E (90%) (55%) Lerwick (28) = 600 08' 0.16 -0.19 -0.02 0.34 0.026 0.045 -0.12 0.34 -0.18 -0.03 -0.03 = 01 ° ll'W (52%) (69%) (92%) (92%) (55%) Rome (28) = 41 ° 54 t -0.13 -0.18 0.13 0.07 0.025 0.43 -0.18 -0.01 -0.23 0.15 -0.05 )~ = 12 o 29' E (69%) (98%) (55%) (65%) (52%) Resolute (27) = 740 43' -0.20 -0.32 0.13 0.19 -0.03 0.07 0.002 -0.21 --0.17 0.02 0.23 A = 940 59' W (65%) (88%) (55°770) (58%) (55%) (65°7o) Reykjavik (24) ---- 64 ° 08' 0.15 -0.29 0.007 0.19 0.03 0.24 -0.05 0.08 -0.25 0.02 0.06 A = 21 ° 54' W (80%) (60%) (78%) (70%) Toronto (25) = 43 ° 40' 0.08 -0.003 0.37 -0.15 -0.14 0.27 0.027 -0.08 -0.17 0.019 -0.09 = 79 o 24' W (92%) (50%) (50%) (80%) (55%) Indeed these same periodic terms appear between the peak-to-peak variation in (r) (Figures la-f). Therefore, we may conclude that there is a high significance for  A CORRELATION STUDY BETWEEN OZONE AND VOLCANIC ACTIVITY 221 TABLE 1JI Correlation coefficient (r) between Ozone and VEI Total and corresponding probability of exceeding (r) in a random sample of observations taken from an uncorrelated parent population (significances S > 50% in parenthesis, in blanks S < 50%). Ozone stations (n) -5 -4 -3 -2 -1 0 1 2 3 4 5 n = number of data Arosa (28) = 46 o 46' ), = 090 40' E Bismarck (25) = 46 ° 46' A = 100 ° 45' W Caribou (23) = 460 52' A = 68 ° 01' W Edmonton (28) ~p = 530 34' A= 113° 31'W Goosebay (23) = 53 ° 20' )~ = 600 25' W Hradec Kr~il6ve (23) = 500 11 r A = 150 50 r E Lerwick (28) = 60 ° 08' A=01 ° ll'W Rome (28) = 410 54' A = 120 29' E Resolute (27) = 740 43' A = 940 59' W Reykjavik (24) qo = 640 08' A = 210 54' W Toronto (25) = 430 40' A = 790 24' W 0.15 0.18 0.14 -0.14 -0.41 -0.12 0.1 -0.21 0.24 0.43 5007o) (60%) (50%) (52%) (97%) (65%) (68°7o) (97%) 0.09 -0.04 -0.03 0.03 0.09 0.11 0.18 -0.25 -0.37 0.025 0.04 0.05 (5807o) (75%) (92%) 0.04 0.08 0.05 -0.2 -0.25 0.28 -0.19 -0.13 0.21 -0.08 -0.03 (80%) (78%) (68%) -0.11 -0.44 -0.23 -0.07 0.026 0.23 0.12 0.04 0.06 -0.15 -0.15 (97%) (68%) (65%) (52%) (50%) 0.36 0.29 0.007 -0.33 -0.32 -0.003 -0.25 -0.01 0..33 0.16 0.23 (88%) (80%) (85%) (85%) (70%) (85°7°) (50%) (65%) 0.06 -0.03 0.01 0.008 -0.52 (98%) 0.36 -0.03 -0.17 -0.09 -0.33 (90%) (58%) (90%) 0.19 -0.13 -0.29 -0.13 -0.47 (60%) (85%) (50%) (98%) 0.13 -0.05 -0.09 -0.41 -0.21 (95%) (65%) 0.25 -0.1 -0.18 -0.18 -0.48 (70%) (58%) (55%) (97%) -0.02 0.04 0.18 -0.04 -0.34 (58%) (90°70) -0.05 0.16 -0.15 0.04 0.22 0.23 (55%) (60%) (65%) -0.09 -0.14 -0.09 0.38 0.19 0.20 (52%) (93%) (60070) (65%) -0.12 0.34 0.09 0.31 0.14 -0.01 90°70) (85%) (50%) 0.37 -0.01 0.t7 0.49 -0.001 -0.37 (93%) (65%) (98%) (90%) 0.02 0.03 0.11 0.41 0.12 -0.005 (95%) 0.11 0.17 -0.21 0.01 0.05 0.12 (55%) (60%) the VEI 2 affecting ozone layer simultaneously or within a lag of 2 years the VEI 2 preceding.
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