TY - JOUR A1 - Scheele, M. P. A1 - Siegmund, P. C. A1 - van Velthoven, P. F. J. T1 - Stratospheric age of air computed with trajectories based on various 3-D-Var and 4-D-Var data sets JO - Atmos. Chem. Phys. Discuss. J1 - ACPD VL - 4 IS - 4 SP - 4489 EP - 4506 Y1 - 2004/08/20 PB - Copernicus Publications SN - 1680-7375 UR - http://www.atmos-chem-phys-discuss.net/4/4489/2004/ L1 - http://www.atmos-chem-phys-discuss.net/4/4489/2004/acpd-4-4489-2004.pdf DO - 10.5194/acpd-4-4489-2004 ER -