Dw. O'Sullivan et al., Distribution of hydrogen peroxide and methylhydroperoxide over the Pacificand South Atlantic Oceans, J GEO RES-A, 104(D5), 1999, pp. 5635-5646
The gas phase hydrogen peroxide and methylhydroperoxide concentrations were
measured in the troposphere over the tropical Pacific Ocean as a component
of NASA's Global Tropospheric Experiment/Pacific Exploratory Mission-Tropi
cs A field campaign. Flights on two aircraft covered the Pacific from 70 de
grees S to 60 degrees N and 110 degrees E to 80 degrees W and South Atlanti
c from 40 degrees S to 15 degrees N and 45 degrees W to 70 degrees E, and e
xtending from 76 to 13,000 m altitude. H2O2 and CH3OOH have the highest con
centrations at a given altitude at the equator and decrease with increasing
latitude in both the northern and southern hemispheres. Above 4 km the gra
dient is substantially reduced for both H2O2 and CH3OOH with latitude, and
at altitudes in excess of 8 km there is no latitudinal dependence. H2O2 and
CH3OOH exhibit maximum mixing ratios between 1 and 2 km at all latitudes.
The mean mixing ratio of H2O2 at the equator was 1600 +/- 600 parts per tri
llion by volume (pptv) decreasing to 500 +/- 250 pptv at latitudes greater
than 550 north and south between 1 and 2 km altitude. CH3OOH at the equator
was 1400 +/- 250 pptv, decreasing to 330 +/- 200 pptv at high latitudes at
altitudes between 1 and 2 km. The concentration of peroxides at high latit
udes in the northern hemisphere was generally a factor of 2 higher than at
corresponding latitudes in the southern hemisphere. The ratio of H2O2 to CH
3OOH was between 1 and 2 from 45 degrees S to 35 degrees N at altitudes bel
ow 4 km. Between 5 degrees to 15 degrees N the ratio is less than 1, due to
preferential removal of H2O2 in the Intertropical Convergence Zone.