2.b. Mean altitude profiles
Altitude profiles of the mean P-O3 for the three tropical basins and the
4 deployments are compared in Figure 1b (for other regions and
reactivities, see Figures S20-S27). For Central Pacific and Tropic
Atlantic, the variation across deployments is not so large with values
~2 ppb/day throughout. ATom-1, however, shows slightly
higher P-O3 (~3 ppb/day) below 4 km in both regions and
also in the upper troposphere but only in the Atlantic.
In the Eastern Pacific, however, each deployment seems unique: ATom-2 is
almost uniform at 2 ppb/day; ATom-134 show enhanced upper troposphere
P-O3 probably from deep convection and lightning NOx over North America;
ATom-13 show large mid-tropospheric production of ~3
ppb/day not seen in ATom-24; and
ATom-4 finds a thick atmospheric
layer, 1-3 km, with an astounding rate of P-O3, averaging
~10 ppb/day. The end of the biomass burning season in
Central America (15°N-20°N) is probably the cause of the peak P-O3 in
ATom-4 (May); while the start of the North American Monsoon season is
probably the cause of the extensive deep-convection layer (8-12+ km)
with high P-O3 in ATom-1 (August). With this high level of variability,
it will be important to re-examine the time period of the ATom flights
with a chemistry-transport model to assess the spatio-temporal scales of
these incredible events. As expected from Figure 1a, the lowest P-O3 in
all 3 tropical basins occurs in northern winter (ATom-2, February). For
L-O3 and L-CH4, the Central Pacific and Tropical Atlantic show little
variability across ATom-1234, but the Eastern Pacific shows the
extremely high reactivities for ATom-14 as found in P-O3 (Figures
S23-S25).
In the Arctic (Figure S26) ATom-14 show nearly identical and constant
profiles for all 3 reactivities; while ATom-23 have negligible
reactivities. P-O3 peaks at 8-12 km with values from 1-2 ppb/day. The
reactivities in the Arctic, even in summer are less than the average
over the Pacific and Atlantic oceans and thus have little impact on the
global O3 or CH4 budgets. In the
Antarctic (Figure S27), reactivities are much less than the Arctic and
only reported for ATom-3.
2.c. Probability densities of photochemical reactivities
The probability densities (PDs) of the ATom reactivities have proven
useful in testing model climatologies (see G2021). Here, we plot the PDs
for the 4 deployments in the major oceanic regions for all 3
reactivities (Figures S28-S33). Overall, we find
ATom-1 has more frequent high
reactivities, and the East Pacific has the least conformity across
ATom-1234. The Central Pacific and Tropical Atlantic provide a
repeatable pattern that should provide an excellent test for CCM
climatologies.