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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. D5, 4170, doi:10.1029/2002JD002525, 2003

N₂O and NO_y observations in the 1999/2000 Arctic polar vortex: Implications for transport processes in a CTM

D. B. Considine

NASA Langley Research Center, Hampton, Virginia, USA

S. R. Kawa

Atmospheric Chemistry and Dynamics Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

M. R. Schoeberl

Atmospheric Chemistry and Dynamics Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

A. R. Douglass

Atmospheric Chemistry and Dynamics Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

Abstract

We compare the evolution of simulated NO_y and N₂O with observations made during the 1999/2000 NASA Stratospheric Aerosol and Gas Experiment (SAGE) III Ozone Loss and Validation Experiment/Third European Stratospheric Experiment on Ozone-2000 to understand the different effects of transport on these two species and evaluate model transport processes in the Arctic lower stratosphere during mid to late winter. The simulations were made with the Goddard Space Flight Center chemistry and transport model, driven by meteorological analyses from the Goddard Data Assimilation Office. In January, model NO_y and N₂O distributions agree well with observations, provided a substantial loss of NO_y due to polar stratospheric cloud sedimentation is included in the model simulation. In late winter, model NO_y is ∼2–3 times larger than observed, despite the continued reasonable agreement of N₂O. Anomalously large vertical transport of NO_y due to overly vigorous descent in the CTM is primarily responsible for the large late winter NO_y mixing ratios. However, the rapid descent is not apparent in the evolution of modeled N₂O and presumably other similar species due to compensating horizontal transport of N₂O across the vortex edge, which results in the reasonable agreement between modeled and measured N₂O at ER-2 altitudes throughout the winter. The need to properly represent the seasonal evolution of NO_y when studying lower stratospheric polar wintertime photochemistry places strong constraints on the meteorological data used to drive global chemistry and transport models.

Published 14 March 2003.

Index Terms: 0340 Atmospheric Composition and Structure: Middle atmosphere—composition and chemistry; 3334 Meteorology and Atmospheric Dynamics: Middle atmosphere dynamics (0341, 0342); 3337 Meteorology and Atmospheric Dynamics: Numerical modeling and data assimilation; 3319 Meteorology and Atmospheric Dynamics: General circulation.

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Citation: Considine, D. B., S. R. Kawa, M. R. Schoeberl, and A. R. Douglass (2003), N₂O and NO_y observations in the 1999/2000 Arctic polar vortex: Implications for transport processes in a CTM, J. Geophys. Res., 108(D5), 4170, doi:10.1029/2002JD002525.

This paper is not subject to U.S. copyright. Published in 2003 by the American Geophysical Union.