[1] During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) aircraft program, ozone depletion events (ODEs) in the high latitude surface layer were investigated using lidar and in situ instruments. Flight legs of 100 km or longer distance were flown 32 times at 30 m altitude over a variety of regions north of 58°between early February and late May 2000. ODEs were found on each flight over the Arctic Ocean but their occurrence was rare at more southern latitudes. However, large area events with depletion to over 2 km altitude in one case were found as far south as Baffin Bay and Hudson Bay and as late as 22 May. There is good evidence that these more southern events did not form in situ but were the result of export of ozone-depleted air from the surface layer of the Arctic Ocean. Surprisingly, relatively intact transport of ODEs occurred over distances of 900-2000 km and in some cases over rough terrain. Accumulation of constituents in the frozen surface over the dark winter period cannot be a strong prerequisite of ozone depletion since latitudes south of the Arctic Ocean would also experience a long dark period. Some process unique to the Arctic Ocean surface or its coastal regions remains unidentified for the release of ozone-depleting halogens. There was no correspondence between coarse surface features such as solid ice/snow, open leads, or polynyas with the occurrence of or intensity of ozone depletion over the Arctic or subarctic regions. Depletion events also occurred in the absence of long-range transport of relatively fresh ''pollution'' within the high latitude surface layer, at least in spring 2000. Direct measurements of halogen radicals were not made. However, the flights do provide detailed information on the vertical structure of the surface layer and, during the constant 30 m altitude legs, measurements of a variety of constituents including hydroxyl and peroxy radicals. A summary of the behavior of these constituents is made. The measurements were consistent with a source of formaldehyde from the snow/ice surface. Median NO x in the surface layer was 15 pptv or less, suggesting that surface emissions were substantially converted to reservoir constituents by 30 m altitude and that ozone production rates were small (0.15-1.5 ppbv/d) at this altitude. Peroxyacetylnitrate (PAN) was by far the major constituent of NO y in the surface layer independent of the ozone mixing ratio.

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[1] During the July 2002 Cirrus Regional Study of Tropical Anvils and Cirrus LayersFlorida Area Cirrus Experiment (CRYSTAL-FACE), flights of a WB-57F aircraft revealed mixing ratios of nitric oxide 10-50 times background over distances of 25-175 km in the anvils of thunderstorms and in clear air downwind of storm systems due to lightning activity and possible transport from the boundary layer. Estimates of the total mass of NO x injected into the middle and upper troposphere differed considerably for a moderately versus highly electrically active storm system as expected. However, assuming that the total mass is dominated by lightning production, rough estimates of the production per average lightning flash for a moderately and a highly active storm also yielded quite different ranges of (0.33-0.66) Â 10 26 and (1.7-2.3) Â 10 26 molecules NO/flash, respectively. If the common assumption is made that intracloud flashes have 1/10th the NO production efficiency of cloud-to-ground (CG) flashes, the ranges of production for the moderately and highly active storms were (0.88-1.8) Â 10 26 and (4.5-6.1) Â 10 26 molecules NO/CG flash, respectively. The observed CG flash accumulations and NO x mass production estimate for the month of July 2002 over the Florida area are compared with results from the MOZART-2 global chemistry-transport model that uses a common lightning flash parameterization. Reasonable agreement was found after a correction to the lightning parameterization was made. Finally, broad-scale median mixing ratios of NO within anvils over Florida were significantly larger than found in storms previously investigated over Colorado and New Mexico.

In July and August of 1989 the National Center for Atmospheric Research (NCAR) Sabreliner jet aircraft was used to probe electrically active and inactive convective storms over west central New Mexico to examine the production of odd nitrogen in the middle and upper troposphere by thunderstorms. In the anvil outflow or cloud top region of active and nonactive storms, the majority of flights showed that O3 was reduced 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, but the reduction in NOy was also enhanced by removal of soluble constituents during convective transport. Examples of efficient removal from the gas phase are described. There was no evidence of O3 production by lightning discharges. Indeed, O3 was a good tracer over the lifetime (∼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, in 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). Thunderstorms 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 amounts 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 is 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 altitude region between 8 km and the top of the thunderstorm anvil (∼11.8 km in these studies). Since in some large‐scale models, lightning‐generated NOx is equally distributed by mass into each tropospheric layer, our estimates are roughly equivalent to those model runs that use a global source strength of about twice our estimate for the upper 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. Apparently, the aircraft was not in the right place at the right time. Thus no estimate of the NOx production by lightning that remains below ∼8 km could be made.

During late July and August 1989, 12 flights of the National Center for Atmospheric Research Sabreliner jet aircraft were made over New Mexico when the region was dominated by either synoptic high pressure or moist “monsoon” flow. In the latter case, sampling was made within and about deep convective clouds which were sometimes electrically active. A summary of the measurements of the species listed in the title and their ratios are given. These distributions include signatures from deep convection, lightning production of odd nitrogen, aircraft exhaust emissions, and possible stratospheric input. The averages and range of these distributions are considered to be more representative of typical summer conditions over the region compared to flights that are often restricted more to fair weather situations. Coherence between the O3 and the NOy observations is compared to results from other ground‐based and aircraft programs and possible contributing factors are discussed. Because the measurements were made with then newly developed instrumentation, its capabilities and shortcomings are summarized.