Lagrangian transport calculations using UARS data. Part I: passive tracers

Abstract

The transport of passive tracers observed by the Upper Atmosphere Research Satellite is simulated using computed three-dimensional trajectories of ~100 000 air parcels initialized on a stratospheric grid, with horizontal winds provided by the United Kingdom Meteorological Office data assimilation system, and vertical (cross isentropic) velocities computed using a fast radiation code. The conservative evolution of trace constituent fields is estimated over 20-30-day periods by assigning to each parcel the observed mixing ratio of the long-lived trace gases N2O and CH4 observed by the Cryogenic Limb Array Etalon Spectrometer (CLAES) and H2O observed by the Microwave Limb Sounder (MLS) on the initialization date. Agreement between calculated and observed fields is best inside the polar vortex and is better in the Arctic than in the Antarctic. -from Authors