Examinando por Autor "Allaart, M."

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Acceso Abierto
A trajectory-based estimate of the tropospheric ozone column using the residual method
(AGU Publishing, 2007-12-19) Schoeberl, M. R.; Ziemke, J. R.; Bojkov, B.; Livesey, N.; Duncan, B.; Strahan, S.; Froidevaux, L.; Kulawik, S.; Bhartia, P. K.; Chandra, S.; Levelt, P. F.; Witte, J. C.; Thompson, A. M.; Cuevas, E.; Redondas, A.; Tarasick, D. W.; Davies, J.; Bodeker, G.; Hansen, G.; Johnson, B. J.; Oltmans, S. J.; Vömel, H.; Allaart, M.; Kelder, H.; Newchurch, M.; Godin Beekmann, S.; Ancellet, G.; Claude, H.; Andersen, S. B.; Kyrö, E.; Parrondo, María Concepción; Yela González, Margarita; Zablocki, G.; Moore, D.; Dier, H.; Von der Gathen, P.; Viatte, P.; Stübi, R.; Calpini, B.; Skrivankova, P.; Dorokhov, V.; De Backer, H.; Schmidlin, F. J.; Coetzee, G.; Fujiwara, M.; Thouret, V.; Posny, F.; Morris, G.; Merrill, J.; Leong, C. P.; Koenig Langlo, G.; Joseph, E.
[1] We estimate the tropospheric column ozone using a forward trajectory model to increase the horizontal resolution of the Aura Microwave Limb Sounder (MLS) derived stratospheric column ozone. Subtracting the MLS stratospheric column from Ozone Monitoring Instrument total column measurements gives the trajectory enhanced tropospheric ozone residual (TTOR). Because of different tropopause definitions, we validate the basic residual technique by computing the 200-hPa-to-surface column and comparing it to the same product from ozonesondes and Tropospheric Emission Spectrometer measurements. Comparisons show good agreement in the tropics and reasonable agreement at middle latitudes, but there is a persistent low bias in the TTOR that may be due to a slight high bias in MLS stratospheric column. With the improved stratospheric column resolution, we note a strong correlation of extratropical tropospheric ozone column anomalies with probable troposphere-stratosphere exchange events or folds. The folds can be identified by their colocation with strong horizontal tropopause gradients. TTOR anomalies due to folds may be mistaken for pollution events since folds often occur in the Atlantic and Pacific pollution corridors. We also compare the 200-hPa-to-surface column with Global Modeling Initiative chemical model estimates of the same quantity. While the tropical comparisons are good, we note that chemical model variations in 200-hPa-to-surface column at middle latitudes are much smaller than seen in the TTOR.
Acceso Abierto
Arctic winter 2005: Implications for stratospheric ozone loss and climate change
(AGU Publishing, 2006-12-08) Rex, M.; Salawitch, R. J.; Deckelmann, H.; Von der Gathen, P.; Harris, N. R. P.; Chipperfield, M. P.; Naujokat, B.; Reimer, E.; Allaart, M.; Andersen, S. B.; Bevilacqua, R.; Braathen, G. O.; Claude, H.; Davies, J.; De Backer, H.; Dier, H.; Dorokhov, V.; Fast, H.; Gerding, M.; Godin Beekmann, S.; Hoppel, K.; Johnson, B.; Kyrö, E.; Litynska, Z.; Moore, D.; Nakane, H.; Parrondo, María Concepción; Risley, A. D.; Skrivankova, P.; Stübi, R.; Viatte, P.; Yushkov, V.; Zerefos, C.
[1] The Arctic polar vortex exhibited widespread regions of low temperatures during the winter of 2005, resulting in significant ozone depletion by chlorine and bromine species. We show that chemical loss of column ozone (ΔO3) and the volume of Arctic vortex air cold enough to support the existence of polar stratospheric clouds (VPSC) both exceed levels found for any other Arctic winter during the past 40 years. Cold conditions and ozone loss in the lowermost Arctic stratosphere (e.g., between potential temperatures of 360 to 400 K) were particularly unusual compared to previous years. Measurements indicate ΔO3 = 121 ± 20 DU and that ΔO3 versus VPSC lies along an extension of the compact, near linear relation observed for previous Arctic winters. The maximum value of VPSC during five to ten year intervals exhibits a steady, monotonic increase over the past four decades, indicating that the coldest Arctic winters have become significantly colder, and hence are more conducive to ozone depletion by anthropogenic halogens.
Acceso Abierto
Chemical ozone loss in the Arctic winter 2002/2003 determined with Match
(EGU European Geosciences Union, 2006-07-10) Streibel, M.; Rex, M.; Von der Gathen, P.; Lehmann, R.; Harris, N. R. P.; Braathen, G. O.; Reimer, E.; Deckelmann, H.; Chipperfield, M.; Millard, G.; Allaart, M.; Andersen, S. B.; Claude, H.; Davies, J.; De Backer, H.; Dier, H.; Dorokov, V.; Fast, H.; Gerding, M.; Kyrö, E.; Litynska, Z.; Moore, D.; Moran, E.; Nagai, T.; Nakane, H.; Parrondo, María Concepción; Skrivankova, P.; Stübi, R.; Vaughan, G.; Viatte, P.; Yushkov, V.
The Match technique was used to determine chemically induced ozone loss inside the stratospheric vortex during the Arctic winter 2002/2003. From end of November 2002, which is the earliest start of a Match campaign ever, until end of March 2003 approximately 800 ozonesondes were launched from 34 stations in the Arctic and mid latitudes. Ozone loss rates were quantified from the beginning of December until mid-March in the vertical region of 400–550 K potential temperature. In accordance with the occurrence of a large area of conditions favourable for the formation of polar stratospheric clouds in December ozone destruction rates varied between 10–15 ppbv/day depending on height. Maximum loss rates around 35 ppbv/day were reached during late January. Afterwards ozone loss rates decreased until mid-March when the final warming of the vortex began. In the period from 2 December 2002 to 16 March 2003 the accumulated ozone loss reduced the partial ozone column of 400–500 K potential temperature by 56±4 DU. This value is in good agreement with that inferred from the empirical relation of ozone loss against the volume of potential polar stratospheric clouds within the northern hemisphere. The sensitivity of the results on recent improvements of the approach has been tested.