Vertical Profiles Of NO2 Research Articles

Measurements of nitric oxide between 0–12 km altitude and 67°N to 60°S latitude obtained during STRATOZ III

Using a chemiluminescent detector, vertical profiles of NO were measured during the STRATOZ III mission from June 4–26, 1984. The mission's flight track started close to Paris, went west across the North Atlantic, south along the east coast of North America and the west coast of South America. It returned north along the east coast of South America, crossed the Atlantic around the equator and continued north along the west coast of North Africa and continental Europe. It covered the latitudes between 67°N and 60°S and the altitudes between 0 and 12 km. The coastal profiles in the northern hemisphere and in the tropics exhibited a C shape, with higher NO concentration values in the planetary boundary layer and the upper troposphere, whereas the measurements over the ocean showed low values in the upper troposphere. The NO mixing ratios in the southern hemisphere, south of 20°S latitude, were lower than in the northern latitudes and showed little increase in the upper troposphere. The two‐dimensional NO distribution along the flight track is derived, and the possible sources of the NO in the high troposphere are briefly discussed.

Zeeman modulation contrasted with pressure modulation in its use in measuring atmospheric NO from the ground

The Zeeman Modulator Radiometer (ZMR), recently built at Oxford to measure the column of NO from the ground by observing the sun, is contrasted with the calculated performance of a pressure modulator radiometer (PMR) observing in the same way. The ZMR is limited in the number of gases that can potentially be measured, but it is more suitable for absorption measurements from the ground because radiometric errors and errors in the correction for other atmospheric absorbers are less important. Both instruments are relatively insensitive to tropospheric NO, although the ZMR is more so. In principle, a PMR containing a variable mean pressure of NO can measure the vertical profile of NO from the ground. The vertical resolution would be 10km between 10 and 25km, and it would measure the total column above 25km. As such it would be especially useful in Antarctica since 10-25 km is the altitude region of the disappearance of ozone there in the spring. Because of its greater energy grasp, the PMR can also make useful measurements observing the moon. Again this would be especially useful in Antarctica, where the stratosphere is sunlit long before the surface.

Stratospheric nitrogen dioxide concentrations as determined from limb brightness measurements made on June 17, 1983

A multiwavelength spectrometer with limb‐scanning optics was developed to make NO2 measurements in the stratosphere. The instrument observes light scattered by aerosol particles and air molecules and measures the differential attenuation of light at different wavelengths by NO2. A vertical profile of NO2 was determined from the brightness measurements, using the results of a single scattering model. The instrument was flown from Palestine, Texas, and observed the stratosphere from an altitude of 33 km at 32°N, 98°W for a period of several hours on the afternoon of June 17, 1983. The mixing ratio of NO2 was observed to be (3.5±0.8) parts per billion by volume (ppbv) at 28 km, in reasonable agreement with solar occultation measurements. The time rate of change of the NO2 concentration at 28 km is estimated at (0.18±0.06) ppbv per hour at 2200 coordinated universal time (CUT).

SAGE observations of stratospheric nitrogen dioxide

The global distribution of nitrogen dioxide in the middle to upper stratosphere (25–45 km altitude) for the period Feburary 1979 to November 1981 has been determined from observations of attenuated solar radiation in the visible region 0.385–0.45 μm by the Stratospheric Aerosol and Gas Experiment (SAGE) satellite instrument. The SAGE‐derived NO2 vertical profiles compare well with observations by balloon and aircraft‐borne sensors. The global SAGE NO2 distributions generally show a maximum in mixing ratio of 8 parts per billion by volume at about 35 km altitude near the equatorial latitudes at local sunset. The location of the mixing ratio peak moves synchronously with the overhead sun for the four different seasons. High‐latitude NO2 column content shows strong seasonal variation, with a maximum in local summer and a minimum in local winter. Selected data at high‐latitude winter seasons are presented, suggesting that the large variation shown could be explained by the coupling of both dynamics and photochemistry of the NOx species. Finally, profiles of the ratio of sunset to sunrise NO2 mixing ratios, peaking at about a factor of 2 at 30 km, are shown.

The oxidation of isoprene in the troposphere: Mechanism and model calculations

A chemical mechanism describing the oxidation of isoprene by OH and O 3 in the troposphere has been developed and incorporated into a one-dimensional steady-state photochemical model. Calculations have been performed for continental conditions at two latitudes, 15°N and 45°N. At 45°N latitude, the effects of anthropogenic hydrocarbon emissions on the vertical profiles of NO x (NO + NO 2) and HNO 3 overshadow the effects of isoprene emissions; at 15°N, the reduced anthropogenic emissions and the increased isoprene emissions produce increases of 26 and 4% in the column contents of NO x and HNO 3, respectively. The integrated columns of CO at 45°N and 15°N latitude increased by 10 and 31 %, respectively, when isoprene chemistry was included, but these increases are much smaller than those that would have been obtained if all the carbon in isoprene had been photochemically transformed into CO. It appears that the fate of a significant quantity of isoprene is in the formation of longer carbon-chain (R > CH 3) oxygenated organic species. The longer carbon-chain alkylhydroperoxides and alkylperoxyacids appear to be important free radical sinks in the tropics given the lower NO x concentrations generally found in the tropics.

Mid-latitude summertime measurements of stratospheric NO2

The vertical distribution of stratospheric nitrogen dioxide was measured during the Atmospheric Environment Service STRATOPROBE projects in August of 1975 and 1976. Vertical profiles of NO2 are determined by measuring the NO2 absorption of sunlight from a balloon platform during sunrise and sunset and inverting the absorption curves. A total of four sunrise/sunset pairs of observations were obtained from balloon flights of August 10 and 17, 1975 and August 19 and 28, 1976. The measurements show significant stability of the NO2 profile from flight to flight with variations of less than 15% between individual profiles. The average NO2 concentration at sunset was found to increase from about 0.3 ppbv at 10 km to 10 ppbv at 35 km. At sunrise the concentrations increase from 0.2 ppbv at 10 km to 5 ppbv at 35 km.

Instantaneous global ozone balance including observed nitrogen dioxide

The catalytic destruction of stratospheric ozone by the oxides of nitrogen is believed to be an important part of the global ozone balance. The lack of sufficient measurements of NO x concentrations has impeded efforts to quantify this process. Recent measurements of stratospheric nitrogen dioxide from ground-based stations as well as aircraft and balloons have provided a first approximation to a global distribution of NO2 vertical columns at sunset. These observed vertical columns have been translated into time-dependent vertical NO2 profiles by means of a one-dimensional atmospheric photochemical model. Using recent observations of air temperature and ozone along with this information, the independent instantaneous (one second) rates of ozone production from oxygen photolysis P(O3), of ozone destruction from pure oxygen species (Chapman reactions) L(O x ), and of ozone destruction by nitrogen oxides L(NO x ) were estimated over the three-dimensional atmosphere. These quantities are displayed as zonal average contour maps, summed over various latitude zones, summed over various altitude bands, and integrated globally between 15 and 45 km. Although the global summation between 15 and 45 km by no means tells the complete story, these numbers are of some interest, and the relative values are: P(O3), 100; L(O x ), 15; L(NO x ), 45±15. It is to be emphasized that this relative NO x contribution to the integrated ozone balance is not a measure of the sensitivity of ozone to possible perturbations of stratospheric NO x ; recent model results must be examined for current estimates of this sensitivity.