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Origin and Variability of Upper Tropospheric Nitrogen Oxides and Ozone at Northern Mid-LatitudesMeasurements of NO(x) and ozone performed during the NOXAR project are compared with results from the coupled chemistry-climate models ECHAM4.L39(DLR)/CHEM and GISS-model. The measurements are based on flights between Europe and the East coast of America and between Europe and the Far East in the latitude range 40 deg N to 65 deg N. The comparison concentrates on tropopause altitudes and reveals strong longitudinal variations of seasonal mean NO,, of 200 pptv. Either model reproduced strong variations 3 km below but not at the tropopause, indicating a strong missing NO(x) or NO(y) sink over remote areas, e.g. NO(x) to HNO3 conversion by OH from additional OH sources or HNO3 wash-out. Vertical profiles show maximum NO(x) values 2-3 km below the tropopause with a strong seasonal cycle. ECHAM4.L39(DLR)/CHEM reproduces a maximum, although located at the tropopause with a less pronounced seasonal cycle, whereas the GISS model reproduces the seasonal cycle but not the profile's shape due to its coarser vertical resolution. A comparison of NO(x) frequency distributions reveals that both models are capable of reproducing the observed variability, except that ECHAM4.L39(DLR)/CHEM shows no very high NO(x) mixing ratios. Ozone mean values, vertical profiles and frequency distributions are much better reproduced in either model, indicating that the NO(x) frequency distribution, namely the most frequent NO(x) mixing ratio, is more important for the tropospheric photochemical ozone production than its mean value. Both models show that among all sources, NO(x) from lightning contributes most to the seasonal cycle of NO(x) at tropopause altitudes. The impact of lightning in the upper troposphere on NO(x) does not vary strongly with altitude, whereas the impact of surface emissions decreases with altitude. However, the models show significant differences in lightning induced NO(x) concentrations, especially in winter, which may be related to the different treatment of the lower stratospheric coupling between dynamics and chemistry.
Document ID
20000060827
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Grewe, V. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Brunner, D. (Royal Netherlands Meteorological Inst. De Bilt, Netherlands)
Dameris, M. (Deutsches Zentrum fuer Luft- und Raumfahrt e.V. Oberpfaffenhofen, Germany)
Grenfell, J. L. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Hein, R. (Deutsches Zentrum fuer Luft- und Raumfahrt e.V. Oberpfaffenhofen, Germany)
Shindell, D. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Staehelin, J. (Eidgenoessische Technische Hochschule Zurich, Switzerland)
Date Acquired
September 7, 2013
Publication Date
January 1, 1999
Subject Category
Environment Pollution
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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