pan=2>
« back to results for ""
Below is a cache of http://www.chem.uci.edu/rowlandblake/publications/186.pdf. It's a snapshot of the page taken as our search engine crawled the Web.
The web site itself may have changed. You can check the current page or check for previous versions at the Internet Archive. Yahoo! is not affiliated with the authors of this page or responsible for its content.
Central/eastern North Pacific photochemical precursor distributions
Central/eastern North Pacific photochemical precursor distributions
for fall/spring seasons as defined by airborne field studies
B. DiNunno,
1
D. Davis,
1
G. Chen,
1
G. Gregory,
2
G. Sachse,
2
B. Anderson,
2
S. Vay,
2
M. Avery,
2
B. Ridley,
3
M. Carroll,
4
J. Walega,
3
D. Montzka,
3
F. Grahek,
3
J. Bradshaw,
1,5
S. Sandholm,
1
Y. Kondo,
6
G. Kok,
7
D. Blake,
8
N. Blake,
8
J. Barrick,
2
H. Fuelberg,
9
B. Martin,
9
and A. Balok
2
Received 9 July 2001; revised 5 April 2002; accepted 10 April 2002; published 30 January 2003.
[
1
]
Data from 10 aircraft programs recorded over the central/eastern North Pacific (180
°
120
°W, 0° 45°N) were assembled for the purpose of assessing an atmospheric chemical
climatology for this region. It represents an early effort at carrying out this task and, thus, it
can be expected to undergo many updates in the future. Such a database is useful in both
gaining further insights concerning the fundamental processes controlling the chemistry of
this region as well as serving as an important baseline by which to evaluate future change.
Critical photochemical precursors examined included O
3
, CO, NO
x
, and H
2
O. In addition,
the distribution profiles for select nonmethane hydrocarbons were explored. The precursor
data were analyzed according to latitude, pressure altitude, and season of the year.
Contrasting the spring and fall measurements, major trends that surfaced in both ozone and
CO included observing elevated levels in spring compared to fall, with the largest spring
increase occurring at latitudes north of 15
°N. Both NO
x
and H
2
O showed trends quite
different from that of CO and O
3
, with an indication of higher mixing ratio levels during the
fall season. Variations in precursor distribution patterns within a season will be explained
based on climatological flow patterns for the region and the resulting connection to source
regions. Where possible, comparisons were performed with other sampling strategies,
including ground-based observations, sonde, and satellite data, and data collected during
shuttle missions. Overall, these comparisons revealed a reasonably high level of
correspondence between the airborne ensemble data and those collected using other
sampling strategies.
I
NDEX
T
ERMS
: 0368 Atmospheric Composition and Structure: Troposphere
constituent transport and chemistry; 1610 Global Change: Atmosphere (0315, 0325); 9355 Information Related
to Geographic Region: Pacific Ocean; K
EYWORDS
: Ozone, Pacific, troposphere, photochemistry
Citation:
DiNunno, B., et al., Central/eastern North Pacific photochemical precursor distributions for fall/spring seasons as defined
by airborne field studies, J. Geophys. Res., 108(D2), 8240, doi:10.1029/2001JD001044, 2003.
1.
Introduction
[
2
] While coming under increasing pressure from anthro-
pogenic influences, the Pacific basin still defines one of the
largest pristine areas left in the world, and thus offers the
potential for providing an atmospheric chemical baseline by
which future change can be measured. It is estimated that in
the near future anthropogenic emissions will substantially
increase in the North Pacific (the principal area of this
study), reflecting estimates showing energy use in eastern
Asia as having increased at a rate of 5% per year for the past
decade [Horowitz and Jacob, 1999]. A continuation in this
increase is expected to lead to increases in NO
x
, CO, and
NMHCs emissions which, in turn, could further modify the
atmosphere in terms of the levels of ozone and other
oxidants [Jacob et al., 1999; Jaffe et al., 1999].
[
3
] Tropospheric patterns of ozone have been the focus of
research for decades [e.g., Fishman and Crutzen, 1978; Liu
et al., 1980; Logan et al., 1981; Levy et al., 1985; Cha-
meides et al., 1987; 1989; Thompson et al., 1993; Davis et
al., 1996; Crawford et al., 1997b; Marenco et al., 1998;
Schultz et al., 1999; Lelieveld and Dentener, 2000]. A major
issue addressed in much of this earlier work has involved
the sorting out of the relative roles of photochemistry and
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. D2, 8240, doi:10.1029/2001JD001044, 2003
1
Department of Earth and Atmospheric Science, Georgia Institute of
Technology, Atlanta, Georgia, USA.
2
NASA Langley Research Center, Hampton, Virginia, USA.
3
Atmospheric Chemistry Division, National Center for Atmospheric
Research, Boulder, Colorado, USA.
4
Department of Atmospheric, Oceanic, and Space Sciences, University
of Michigan, Ann Arbor, Michigan, USA.
5
Deceased 16 June 1997.
6
Research Center for Advanced Science and Technology, University of
Tokyo, Japan.
7
Research Aviation Facility, National Center for Atmospheric Research,
Boulder, Colorado, USA.
8
Department of Chemistry, University of California, Irvine, California,
USA.
9
Department of Meteorology, Florida State University, Tallahassee,
Florida, USA.
Copyright 2003 by the American Geophysical Union.
0148-0227/03/2001JD001044$09.00
PEM
12
-
1 stratospheric transport in controlling ozone levels in the
troposphere. Of particular interest has been explaining the
presence of the late winter-early spring northern hemi-
spheric maximum in midlatitude ozone [Yienger et al.,
1999; Monks, 2000, and references therein]. More recently
the issue of the effect of long range transport of Asian
generated ozone precursors on west coast USA ozone levels
has also been raised [Jacob et al., 1999; Jaffe et al., 1999;
Yienger et al., 1999].
[
4
] Centrally important to chemically assessing each of
these ozone issues is having available reliable northern
hemispheric distributions of ozone precursor species. The
most critical of these are shown in Figure 1 and, for marine
regions, include H
2
O, CO, NO
x
and O
3
. Also indicated as
potentially important are NMHCs. However, this chemical
familys importance, appears to only become significant as
continental land areas are approached. As discussed below,
the current effort will be focused only on the northeastern
Pacific ocean basin.
[
5
] Numerous aircraft field campaigns have been con-
ducted in the Pacific basin from which a precursor database
can be assembled. One of the earliest of these goes back to
project GAMETAG [Davis, 1980]. GAMETAG, like many
of the programs that followed, passed through the central and
eastern North Pacific on their way to specific study regions
(see Figure 2). The two Pacific Exploratory Missions West
(PEM-West A and B) programs focused on the northwestern
Pacific with special emphasis on the Asian Pacific rim [Hoell
et al., 1996, 1997]. The first Aerosol Characterization
Experiment (ACE 1) examined the Southern Ocean [Bates
et al., 1998]. PEM-Tropics A and B [Hoell et al., 1999;
Raper et al., 2001] explored the chemistry of the tropical
Pacific as did the second Mauna Loa Observatory Photo-
chemistry Experiment (MLOPEX II) which was focused on
the island of Hawaii [Atlas and Ridley, 1996]. By contrast,
the Chemical Instrumentation Test and Evaluation programs
(CITE-1C and CITE-2) sampled primarily the eastern North
Pacific, with much of this activity occurring just off the coast
of California [Hoell et al., 1990]. CITE-1B [Beck et al.,
1987] sampled both off the coast of California as well as the
region surrounding Hawaii.
[
6
] The specific area of interest in this study is the central/
eastern North Pacific (CENP) as defined by the coordinates
180
° 120°W and 0° 45°N. The chemical climatology
derived from the past 20 years of aircraft measurements
should prove especially useful in establishing baseline
values for future research studies, in particular for compar-
isons to future satellite observations [Connors et al., 1999].
In a companion paper, DiNunno et al. [2002] will present a
detailed examination of how the precursor data relate to the
ozone budget for the CENP region.
2.
Database
[
7
] The CENP region has been defined here as being
bound on the west by the international dateline, on the east
by the west coast of North America, and on the south by the
equator. The northern limit has been constrained by latitudes
beyond which there is little or no aircraft data.
[
8
] As noted earlier, the species of primary interest in this
study are O
3
, CO, NO
x
, and H
2
O. Also examined from the
perspective of their use as tracers will be the nonmethane
hydrocarbon (NMHC) species C
3
H
8
and C
2
H
2
. The former
species are critical to defining the photochemical environ-
ment within the CENP. But they also represent species for
which there is a long history of successful observations.
[
9
] In this analysis, data components from ten di