HR: 11:05h
AN: A11H-04    [PDF]
TI: Evidence That Ambient Nitric Acid Increases Relative Humidity in Low-Temperature Cirrus Clouds
AU: * Gao, R S
EM: rgao@al.noaa.gov
AF: Aeronomy Laboratory, National Oceanic and Atmospheric Administration, boulder, CO 80305 United States
AU: Popp, P J
EM: ppopp@al.noaa.gov
AF: Aeronomy Laboratory, National Oceanic and Atmospheric Administration, boulder, CO 80305 United States
AU: Popp, P J
EM: ppopp@al.noaa.gov
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Fahey, D W
EM: dfahey@al.noaa.gov
AF: Aeronomy Laboratory, National Oceanic and Atmospheric Administration, boulder, CO 80305 United States
AU: Fahey, D W
EM: dfahey@al.noaa.gov
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Marcy, T P
EM: tmarcy@al.noaa.gov
AF: Aeronomy Laboratory, National Oceanic and Atmospheric Administration, boulder, CO 80305 United States
AU: Marcy, T P
EM: tmarcy@al.noaa.gov
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Herman, R L
EM: robert.l.herman@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 United States
AU: Weinstock, E M
EM: weinstock@huarp.harvard.edu
AF: Atmospheric Research Project, Harvard University, Cambridge, MA 02138 United States
AU: Baumgardner, D G
EM: darrel@servidor.unam.mx
AF: Universidad Nacional Autonoma de Mexico, Centro de Ciencias de la AtmosferaUniversitaria, Mexico DF, 04510 Mexico
AU: Garrett, T J
EM: tgarrett@met.utah.edu
AF: Department of Meteorology, University of Utah, Salt Lake City, UT 84112 United States
AU: Rosenlof, K H
EM: krosenlof@al.noaa.gov
AF: Aeronomy Laboratory, National Oceanic and Atmospheric Administration, boulder, CO 80305 United States
AU: Thompson, T L
EM: tlt@al.noaa.gov
AF: Aeronomy Laboratory, National Oceanic and Atmospheric Administration, boulder, CO 80305 United States
AU: Bui, P T
EM: pbui@mail.arc.nasa.gov
AF: Ames Research Center, NASA, Moffett Field, CA 94035 United States
AU: Ridley, B A
EM: ridley@acd.ucar.edu
AF: Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO 80307 United States
AU: Wofsy, S C
EM: scw@io.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138 United States
AU: Toon, O B
EM: toon@lasp.colorado.edu
AF: Laboratory for Atmospheric and Space Physics, Program in Atmospheric and Oceanic Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Tolbert, M A
EM: tolbert@cires.colorado.edu
AF: Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309 United States
AU: Karcher, B
EM: ernd.kaercher@dlr.de
AF: Institut f�r Physik der Atmosph„re, Deutsches Zentrum f�r Luft- und Raumfahrt, Wessling, 82234 Germany
AU: Peter, T
EM: thomas.peter@ethz.ch
AF: Laboratorium fuer Atmosph„renphysik, ETH-Zurich, Zurich, CH-8093 Switzerland
AU: Hudson, P K
EM: phudson@al.noaa.gov
AF: Aeronomy Laboratory, National Oceanic and Atmospheric Administration, boulder, CO 80305 United States
AU: Hudson, P K
EM: phudson@al.noaa.gov
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Weinheimer, A J
EM: wein@ncar.ucar.edu
AF: Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO 80307 United States
AU: Heymsfield, A J
EM: heyms1@ncar.ucar.edu
AF: Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO 80307 United States
AB: In situ measurements of the relative humidity with respect to ice (RH$_i$) and nitric acid (HNO$_3$) were made in both natural and contrail cirrus clouds in the upper troposphere. At temperatures lower than 202K, RH$_i$ values show a sharp increase to average values over 130% in both cloud types. These enhanced RH$_i$ values are attributed to the presence of a new class of HNO3-containing ice particles. We propose that these particles have HNO$_3$-trihydrate-like clusters or partial layers which interfere with the ice-vapor steady state. These RH$_i$ observations alter expected cloud properties in the upper troposphere and the effectiveness of the dehydration process. The potential role for HNO$_3$ represents a new link between natural and anthropogenic nitrogen oxide emissions and climate change.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting