Large‐scale ozone and aerosol distributions, air mass characteristics, and ozone fluxes over the western Pacific Ocean in late winter/early spring

Abstract

[1] Large-scale measurements of ozone (O 3 ) and aerosol distributions were made from the NASA DC-8 aircraft during the Transport and Chemical Evolution over the Pacific (TRACE-P) field experiment conducted in February-April 2001. Remote measurements were made with an airborne lidar to provide O 3 and multiple-wavelength aerosol backscatter profiles from near the surface to above the tropopause along the flight track. In situ measurements of O 3 , aerosols, and a wide range of trace gases were made onboard the DC-8. Five-day backward trajectories were used in conjunction with the O 3 and aerosol distributions on each flight to indicate the possible origin of observed air masses, such as from biomass burning regions, continental pollution, desert regions, and oceanic regions. Average latitudinal O 3 and aerosol scattering ratio distributions were derived from all flights west of 150°E, and these distributions showed the average latitude and altitude dependence of different dynamical and chemical processes in determining the atmospheric composition over the western Pacific. TRACE-P (TP) showed an increase in the average latitudinal distributions of both O 3 and aerosols compared to PEM-West B (PWB), which was conducted in February-March 1994. O 3 , aerosol, and potential vorticity levels were used to identify nine air mass types and quantify their frequency of occurrence as a function of altitude. This paper discusses the characteristics of the different air mass types encountered during TP and compares them to PWB. These results confirmed that most of the O 3 increase in TP was due to photochemistry. The average latitudinal eastward O 3 flux in the western Pacific during TP was found to peak near 32°N with a total average O 3 flux between 14 and 46°N of 5.2 Tg/day. The eastward total CO flux was calculated to be 2.2 Tg-C/day with $6% estimated from Asia. The Asian flux of CO 2 and CH 4 was estimated at 4.9 and 0.06 Tg-C/day.

Factors influencing the large-scale distribution of Hg° in the Mexico City area and over the North Pacific

“…6). The associated air masses most likely originated at low altitude over the equatorial Atlantic and were lifted to higher altitudes by convective activity, as observed over the Pacific on previous DC-8 airborne missions (Browell et al, 1996(Browell et al, , 2001(Browell et al, , 2003a. The fact that Hg • did not follow the sharply decreased altitudinal trend of CO (Fig.…”

Detailed comparisons of airborne formaldehyde measurements with box models during the 2006 INTEX-B and MILAGRO campaigns: potential evidence for significant impacts of unmeasured and multi-generation volatile organic carbon compounds

“…Numerous diagnostics from ground, airborne, and balloon-sounding systems indicated uniform sampled air between the airborne and ground-based measurements. These diagnostics include: airborne aerosol measurements using the NASA Langley lidar system on the DC-8 (Browell et al, 2003) and the NCAR SABL Lidar system on the C-130, a ground-based micro-pulsed lidar system located at T 1 , 915 MHz radar wind profilers operated by Phillips and Knupp at the University of Alabama (see Cronce et al, 2007) and a Ceilometer backscatter profiler, and balloon soundings of constant potential temperature.…”

“…This gas, which is the most abundant aldehyde compound found in the atmosphere, is formed from the oxidation of most anthropogenic and biogenic hydrocarbons, primarily initiated by reactions with the hydroxyl (OH) radical and ozone (O 3 ). Formaldehyde is also directly emitted into the atmosphere from biomass burning ; incomplete combustion from motor vehicles (Herndon et al, 2005), potentially from petrochemical flares (Olaguer et al, 2009) and other sources; industrial emissions, and by emissions from vegetation (Carlier et al, 1986, and references therein). Typical atmospheric mixing ratios vary from approximately 1 part-per-billion by volume (1 ppbv, 1 part in 10 9 parts of air) in the background continental boundary layer to several 10's of ppbv for polluted air over urban regions (Dasgupta et al, 2005) and air influenced by petrochemical refinery emissions (primarily ethene and propene) during summer months (Wert et al, 2003).…”

Validation of Tropospheric Emission Spectrometer ozone profiles with aircraft observations during the Intercontinental Chemical Transport Experiment–B

“…DIAL is unable to measure ozone at the aircraft altitude or in close proximity to it, so this part of the profile is estimated by interpolating between the nadir and zenith O 3 profiles by using a third-order polynomial least squares fit that is constrained to pass through the in situ O 3 value measured on the DC-8 by FASTOZ (see section 2.3) [Browell et al, 1996]. The airborne DIAL system has been used in many tropospheric chemistry studies including recent investigations of O 3 and aerosols during the TRACE-P (Transport and Chemical Evolution over the Pacific) [Browell et al, 2003a] and TOPSE (Tropospheric Ozone Production about the Spring Equinox) [Browell et al, 2003b] field experiments. Figure 2 shows an example of DIAL ozone measurements together with the corresponding error profiles obtained during an INTEX-B flight.…”