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An analysis of large HNO_3-containing particles sampled in the Arctic stratosphere during the winter of 1999/2000

Northway, M. J. and Gao, R. S. and Popp, P. J. and Holecek, J. C. and Fahey, D. W. and Carslaw, K. S. and Tolbert, M. A. and Lait, L. R. and Dhaniyala, S. and Flagan, R. C. and Wennberg, P. O. and Mahoney, M. J. and Herman, R. L. and Toon, G. C. and Bui, T. P. (2002) An analysis of large HNO_3-containing particles sampled in the Arctic stratosphere during the winter of 1999/2000. Journal of Geophysical Research. Atmospheres, 107 (D20). Art. No. 8298. ISSN 2169-897X. doi:10.1029/2001JD001079.

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Large (>2 μm diameter) HNO_3-containing polar stratospheric cloud (PSC) particles were measured in situ by the NOAA NO_y instrument on board the NASA ER-2 aircraft during seven flights in the 1999/2000 Arctic winter vortex. Here we discuss the detection of these large PSC particles, their spatial distribution, the ambient conditions under which they were detected, and our methods for interpreting NO_y time series with respect to particle sizes and number concentrations. The particles were observed through the use of two NO_y inlets on a particle separator extending below the ER-2 aircraft. The particle phase is assumed to be nitric acid trihydrate (NAT) or nitric acid dihydrate (NAD). Over a 48-day period, particles were sampled in the Arctic vortex over a broad range of latitudes (60–85°N) and altitudes (15–21 km). Typically, regions of the atmosphere up to 4 km above the observed large particle clouds were saturated with respect to NAT. Occasionally, large particles were measured in air subsaturated with respect to NAT, suggesting ongoing particle evaporation. Vortex minimum temperatures in the observation period suggest that synoptic-scale ice saturation conditions are not required for the formation of this type of particle. Three analytical methods are used to estimate size and number concentrations from the NO_y time series. Results indicate particle sizes between 5 and 20 μm diameter and concentrations from 10^(−5) to 10^(−3) cm^(−3). These low number concentrations imply a selective nucleation mechanism. Particle sizes and number concentrations were greater during the midwinter flights than the late winter flights. Knowledge of the geographical extent of large particles, actual sampling conditions, and particle size distributions offers multiple constraints for atmospheric models of PSC formation, which will lead to a better understanding of the process of denitrification and improvements in modeling future ozone loss.

Item Type:Article
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Flagan, R. C.0000-0001-5690-770X
Wennberg, P. O.0000-0002-6126-3854
Toon, G. C.0000-0003-4174-7541
Additional Information:© 2002 American Geophysical Union. Received 9 July 2001; revised 28 November 2001; accepted 1 December 2002; published 24 October 2002. The authors wish to thank the NASA ER-2 pilots J. Barrilleaux, J. Nystrom, and D. Porter and ground crew; Richard Winkler for his programming assistance; and Rich McLaughlin for assistance with Figure 2. This work was supported by the NASA Upper Atmosphere Research Program. Work at the Jet Propulsion Laboratory, California Institute of Technology, was carried out under contract with the National Aeronautics and Space Administration. Some of the material presented is based upon work supported by the National Science Foundation under award ATM-9871353, P. Wennberg, P.I.
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Subject Keywords:polar stratospheric clouds; particles; denitrification; HNO_3; NAT; NO_y
Issue or Number:D20
Record Number:CaltechAUTHORS:20150818-100656143
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Official Citation:Northway, M. J., et al., An analysis of large HNO3-containing particles sampled in the Arctic stratosphere during the winter of 1999/2000, J. Geophys. Res., 107(D20), 8298, doi:10.1029/2001JD001079, 2002.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59681
Deposited By: Irina Meininger
Deposited On:20 Aug 2015 20:17
Last Modified:10 Nov 2021 22:23

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