Examinando por Autor "Reimer, E."

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Acceso Abierto
Arctic ozone loss in threshold conditions: Match observations in 1997/1998 and 1998/1999
(American Geophysical Union, 2001-04-01) Schulz, Astrid; Rex, Markus; Harris, Neil R. P.; Braathen, Geir O.; Reimer, E.; Alfier, R.; Kilbane Dawe, Iarla; Eckermann, Stephen; Allaart, Marc; Alpers, Matthias; Bojkov, B; Cisneros Sanchiz, Juan María; Claude, H.; Cuevas Agulló, Emilio; Davies, Jonathan; Backer, Hugo de; Dier, Horst; Dorokhov, Valery; Fast, Hans; Godin, Sophie; Johnson, B. J.; Kois, Bogumil; Kondo, Yutaka; Kosmidis, Evangelos; Kyrö, Esko; Litynska, Z.; Mikkelsen, I. S.; Molyneux, M. J.; Murphy, Gerry; Nagai, T.; Nakane, Hideaki; O'Connor, Fiona M.; Parrondo, María Concepción; Schmidlin, Frank J.; Skrivánková, Pavla; Varotsos, Costas; Vialle, C.; Viatte, P.; Yushkov, Vladimir; Zerefos, Christos S.; Gathen, Peter von der; European Commission (EC)
Chemical ozone loss rates inside the Arctic polar vortex were determined in early 1998 and early 1999 by using the Match technique based on coordinated ozonesonde measurements. These two winters provide the only opportunities in recent years to investigate chemical ozone loss in a warm Arctic vortex under threshold conditions, i.e., where the preconditions for chlorine activation, and hence ozone destruction, only occurred occasionally. In 1998, results were obtained in January and February between 410 and 520 K. The overall ozone loss was observed to be largely insignificant, with the exception of late February, when those air parcels exposed to temperatures below 195 K were affected by chemical ozone loss. In 1999, results are confined to the 475 K isentropic level, where no significant ozone loss was observed. Average temperatures were some 8°–10° higher than those in 1995, 1996, and 1997, when substantial chemical ozone loss occurred. The results underline the strong dependence of the chemical ozone loss on the stratospheric temperatures. This study shows that enhanced chlorine alone does not provide a sufficient condition for ozone loss. The evolution of stratospheric temperatures over the next decade will be the determining factor for the amount of wintertime chemical ozone loss in the Arctic stratosphere.
Acceso Abierto
Chemical depletion of Arctic ozone in winter 1999/2000
(American Geophysical Union, 2002-09-20) Rex, Markus; Salawitch, R. J.; Harris, Neil R. P.; Gathen, Peter von der; Braathen, Geir O.; Schulz, Astrid; Deckelmann, H.; Chipperfield, M.; Sinnhuber, B. M.; Reimer, E.; Alfier, R.; Bevilacqua, R.; Hoppel, K.; Fromm, M.; Lumpe, J.; Küllmann, H.; Kleinböhl, A.; Bremer, H.; Von König, M.; Künzi, K.; Toohey, D.; Vömel, H.; Richard, E.; Aikin, K.; Jost, H.; Greenblatt, J. B.; Loewenstein, M.; Podolske, J. R.; Webster, Christopher R.; Flesch, Gregory J.; Scott, D. C.; Herman, R. L.; Elkins, J. W.; Ray, E. A.; Moore, F. L.; Hurst, D. F.; Romashkin, P.; Toon, G. C.; Sen, B.; Margitan, J. J.; Wennberg, P.; Neuber, R.; Allart, M.; Bojkov, B. R.; Claude, H.; Davies, Jonathan; Davies, W.; De Backer, H.; Dier, Horst; Dorokhov, Valery; Fast, H.; Kondo, Yutaka; Kyrö, E.; Litynska, Z.; Mikkelsen, I. S.; Molyneux, M. J.; Moran, E.; Nagai, T.; H. Nakane; Parrondo, María Concepción; Ravegnani, Fabrizio; Skrivánková, Pavla; Viatte, P.; Yushkov, Vladimir; European Commission (EC); National Aeronautics and Space Administration (NASA)
[1] During Arctic winters with a cold, stable stratospheric circulation, reactions on the surface of polar stratospheric clouds (PSCs) lead to elevated abundances of chlorine monoxide (ClO) that, in the presence of sunlight, destroy ozone. Here we show that PSCs were more widespread during the 1999/2000 Arctic winter than for any other Arctic winter in the past two decades. We have used three fundamentally different approaches to derive the degree of chemical ozone loss from ozonesonde, balloon, aircraft, and satellite instruments. We show that the ozone losses derived from these different instruments and approaches agree very well, resulting in a high level of confidence in the results. Chemical processes led to a 70% reduction of ozone for a region ∼1 km thick of the lower stratosphere, the largest degree of local loss ever reported for the Arctic. The Match analysis of ozonesonde data shows that the accumulated chemical loss of ozone inside the Arctic vortex totaled 117 ± 14 Dobson units (DU) by the end of winter. This loss, combined with dynamical redistribution of air parcels, resulted in a 88 ± 13 DU reduction in total column ozone compared to the amount that would have been present in the absence of any chemical loss. The chemical loss of ozone throughout the winter was nearly balanced by dynamical resupply of ozone to the vortex, resulting in a relatively constant value of total ozone of 340 ± 50 DU between early January and late March. This observation of nearly constant total ozone in the Arctic vortex is in contrast to the increase of total column ozone between January and March that is observed during most years.
Acceso Abierto
Match observations in the Arctic winter 1996/97: High stratospheric ozone loss rates correlate with low temperatures deep inside the polar vortex
(American Geophysical Union, 2020-01-15) Schulz, Astrid; Rex, Markus; Steger, J.; Harris, Neil R. P.; Braathen, Geir O.; Reimer, E.; Alfier, R.; Beck, A.; Alpers, Matthias; Cisneros Sanchiz, Juan María; Claude, H.; De Backer, Hugo; Dier, Horst; Dorokhov, Valery; Fast, Hans; Godin, Sophie; Hansen, Georg; Kanzawa, Hiroshi; Kois, Bogumil; Kondo, Yutaka; Kosmidis, Evangelos; Kyrö, Esko; Litynska, Z.; Molyneux, M. J.; Murphy, Gerry; Nakane, Hideaki; Parrondo, María Concepción; Ravegnani, Fabrizio; Varotsos, Costas; Vialle, C.; Viatte, P.; Yushkov, Vladimir; Zerefos, Christos S.; Gathen, Peter von der
With the Match technique, which is based on the coordinated release of ozonesondes, chemical ozone loss rates in the Arctic stratospheric vortex in early 1997 have been quantified in a vertical region between 400 K and 550 K. Ozone destruction was observed from mid February to mid March in most of these levels, with maximum loss rates between 25 and 45ppbv/day. The vortex averaged loss rates and the accumulated vertically integrated ozone loss have been smaller than in the previous two winters, indicating that the record low ozone columns observed in spring 1997 were partly caused by dynamical effects. The observed ozone loss is inhomogeneous through the vortex with the highest loss rates located in the vortex centre, coinciding with the lowest temperatures. Here the loss rates per sunlit hour reached 6 ppbv/h, while the corresponding vortex averaged rates did not exceed 3.9 ppbv/h.