Ba. Ridley et al., ON THE PRODUCTION OF ACTIVE NITROGEN BY THUNDERSTORMS OVER NEW-MEXICO, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 101(D15), 1996, pp. 20985-21005
In July and August of 1989 the National Center for Atmospheric Researc
h (NCAR) Sabreliner jet aircraft was used to probe electrically active
and inactive convective storms over west central New Mexico to examin
e the production of odd nitrogen in the middle and upper troposphere b
y thunderstorms. In the anvil outflow or cloud top region of active an
d nonactive storms, the majority of flights showed that O-3 was reduce
d relative to the extracloud air owing to transport of ozone-poor air
from lower altitudes. A similar result was found for active nitrogen (
NOx) and total odd nitrogen (NOy) in nonelectrically active storms, bu
t the reduction in NOy was also enhanced by removal of soluble constit
uents during convective transport. Examples of efficient removal from
the gas phase are described. There was no evidence of O-3 production b
y lightning discharges. Indeed, O-3 was a goad tracer over the lifetim
e (similar to 1 hour) of the storms. During the active-to-mature stage
of air mass thunderstorms, large enhancements in active nitrogen were
observed in the anvil altitude region (9-11.8 km) and, in one case, i
n the midlevel outflow (near 7 km) of a dissipating thunderstorm. Two
thunderstorms allow good estimates of the NOx production by lightning
within or transport to the upper altitude region (8-11.8 km). Thunders
torms of August 12 and August 19 yield amounts in the range of 253-296
kg(N) and 263-305 kg(N), respectively. If, as an exercise, these amou
nts are extrapolated to the global scale on the basis of the number of
cloud-to-ground and intracloud lightning flashes counted or estimated
for each storm and a global flash frequency of 100 s(-1) the result i
s 2.4-2.7 and 2.0-2.2 Tg(N)/yr. Alternatively, an estimate for the two
storms made on the basis of the average number of thunderstorms that
occur per day globally (44,000) yields amounts in the range of 4.1-4.7
and 4.2-4.9 Tg(N)/yr, respectively. These estimates only apply to the
production or transport of lightning generated NOx in or to the altit
ude region between 8 km and the top of the thunderstorm anvil (similar
to 11.8 km in these studies). Since in some large-scale models, light
ning-generated NOx is equally distributed by mass into each tropospher
ic layer, our estimates are roughly equivalent to those model runs tha
t use a global source strength of about twice our estimate for the upp
er altitude region. In several flights where the region below the base
of thunderstorms was examined, no large enhancements in odd nitrogen
which could be clearly attributed to lightning were observed. Apparent
ly, the aircraft was not in the right place at the right time. Thus no
estimate of the NOx production by lightning that remains below simila
r to 8 km could be made.