Upper Troposphere/Lower Stratosphere

In the upper troposphere/lower stratosphere (UTLS) region sources of NOx are small, from large scale convective updrafts, stratospheric sources, aircraft and lightning. We have used the monthly mean totals of lightning NOx from the GEIA inventory (scaled from 12.2 to 2 Tg/yr) and distributed them in the horizontal according to the convective cloud distribution of the model. 

For typical soot aggregates in the upper troposphere/lower stratosphere the enhancement factor is in the range 2.7 to 3.5 (Figure 9.9). This is an order of magnitude lower that that used in modelling studies [126]. 

The upper troposphere/lower stratosphere (UT/LS) have been identified as altitude regions with high sensitivity to antropogeneous perturbations in connection with a possibly large impact on ozone depletion and climate. Predictions of antropogeneous influence are limited by imcertainties in our knowledge of trace gas effects on composition and heterogeneous activity of ice particles which were formed in the natural cirrus troposphere clouds and PSCs, and contrail clouds. 

Fig. 1-8. Eddy diffusion coefficients in the northern hemisphere. Upper frame Lower stratosphere (lOOmbar, about 16km altitude) curve 1 for December-January, curve 2 for June-August, approximated from Luther (1975) and Hidalgo and Crutzen (1977). Lower frame One-dimensional Kv values for the troposphere after Czeplak and Junge (1974) curve 3 based on wind variance data of Flohn (1961) and Newell el al. (1966) curve 4 based on data of Newell et al. (1972), annual average.

The tropical tropopause, essentially defined by the 380 K potential temperature surface (see Chapter 21), is located at about 16-17 km. Tropical convection occurs up to an altitude of about 11-12 km. Between these two levels lies a transition region between the tropopause and the stratosphere, call the tropica tropopause layer (TTL). Together with the lowermost stratosphere, the region is referred to as the upper troposphere/lower... 

Hauck G and Arnold F 1984 Improved positive-ion composition measurements in the upper troposphere and lower stratosphere and the detection of acetone Nature 311 547-50... 

Considering natural stratospheric ozone pro-duction/destruction as a balanced cycle, the NO.v reaction sequence is responsible for approximately half of the loss in the upper stratosphere, but much less in the lower stratosphere (Wennberg et al, 1994). Since this is a natural steady-state process, this is not the same as a long term O3 loss. The principal source of NO to the stratosphere is the slow upward diffusion of tropospheric N2O, and its subsequent reaction with O atoms, or photolysis (McElroy et ai, 1976). 

Arnold, F., V. Burger, B. Droste-Fanke, F. Grimm, A. Krieger, J. Schneider, and T. Stilp, Acetone in the Upper Troposphere and Lower Stratosphere Impact on Trace Gases and Aerosols, Geophys. Res. Lett., 24, 3017-3020 (1997b). 

Iraci, L. T and M. A. Tolbert, Heterogeneous Interaction of Formaldehyde with Cold Sulfuric Acid Implications for the Upper Troposphere and Lower Stratosphere, . /. Geophys. Res., 102, 16099-16107 (1997). 

Assume HN03 is in a steady state. Calculate the ratio [N02]/[HN03] at a temperature of 300 K and 1 atm pressure using the DeMore et al. (1997) recommendations and those of Brown et al. (1999a, 1999b). For (a) T = 300 K and P = 1 atm and (b) T = 220 K and P = 150 Torr, characteristic of the lower stratosphere/ upper troposphere, would the revised kinetics be expected to bring the measurements and models into better agreement ... 

Choi, W., and M.-T. Leu, Nitric Acid Uptake and Decomposition on Black Carbon (Soot) Surfaces Its Implications for the Upper Troposphere and Lower Stratosphere, J. Phys. Chem. A, 102, 7618-7630 (1998). 

Sheridan, P. J., C. A. Brock, and J. C. Wilson, Aerosol Particles in the Upper Troposphere and Lower Stratosphere Elemental Composition and Morphology of Individual Particles in Northern Midlatitudes, Geophys. Res. Lett., 21, 2587-2590 (1994). 

With HCN concentrations of 170 ppt in the stratosphere and upper troposphere (Coffey et al., 1981 Cicerone and Zellner, 1983 Zander et al., 1988 Schneider et al., 1997), and up to 900 ppt at times (Rinsland et al., 1998), HCN could contribute significantly to NO, depending on the conversion efficiency. The same is true of acetonitrile, CH3CN, whose concentrations are less well known it has been measured over Europe at concentrations in the range of 150-200 ppt (e.g., Hamm et al., 1989) and in the lower stratosphere at concentrations of 110-160 ppt (Schneider et al., 1997). However, much smaller concentrations, of the order of a few tens of ppt, have also been reported in the atmosphere (Knop and Arnold, 1987a, 1987b). High concentrations of NH3 are quite common in the troposphere, particularly near sources such as cattle feedlots (vide infra). 

Zander, R., C. P. Rinsland, C. B. Farmer, J. Namkung, R. H. Norton, and J. M. Russell III, Concentrations of Carbonyl Sulfide and Hydrogen Cyanide in the Free Upper Troposphere and Lower Stratosphere Deduced from ATMOS/Spacelab 3 Infrared Solar Occultation Spectra, . /. Geophys. Res., 93, 1669-1678(1988). 

Because of these rapid removal processes in the troposphere, the contribution of iodine to stratospheric photochemistry has not received much attention. However, Solomon et al. (1994) suggested that rapid transport from the lower troposphere into the upper troposphere and lower stratosphere via convective clouds could provide a mechanism for injecting such compounds into the stratosphere. While the relevant chemistry of iodine is not well known, it would be expected to interact with the CIO cycles in much the same way as BrO, e.g.,... 

Blake, D. F., and K. Kato, Latitudinal Distribution of Black Carbon Soot in the Upper Troposphere and Lower Stratosphere, J. Geophys. Res., 100, 7195-7202 (1995). 

Brasseur, G. P., X. Tie, P. J. Rasch, and F. Lefevre, A Three-Dimensional Simulation of the Antarctic Ozone Hole Impact of Anthropogenic Chlorine on the Lower Stratosphere and Upper Troposphere, J. Geophys. Res., 102, 8909-8930 (1997). 

In addition, there is an obseived correlation between total column ozone and the El Nino Southern Oscillation (ENSO) in the tropical troposphere, with decreases in total ozone in middle and sometimes polar latitudes following the ENSO by several months the period associated with the ENSO is 43 months (Zerefos et al., 1992). While the association between the ENSO and ozone is not well understood, it has been proposed that the warming of the troposphere in the tropics over the Pacific Ocean causes increases in the upper troposphere air temperatures and tropopause height and an upwelling in the lower stratosphere. If sufficiently large, this could have more widespread impact than just in the tropics (e.g., see Zerefos et al., 1992 and Kalicharran et al., 1993). 

Volcanic eruptions provide one test of the relationship between light scattering by sulfate particles and the resulting change in temperature, since they generate large concentrations of sulfate aerosol in the lower stratosphere and upper troposphere. These aerosol... 

Mechanisms and rates of transport of nuclear test debris in the upper and lower atmosphere are considered. For the lower thermosphere vertical eddy diffusion coefficients of 3-6 X 106 cm.2 sec. 1 are estimated from twilight lithium enhancement observations. Radiochemical evidence for samples from 23 to 37 km. altitude at 31° N indicate pole-ward mean motion in this layer. Large increases in stratospheric debris in the southern hemisphere in 1963 and 1964 are attributed to debris from Soviet tests, transported via the mesosphere and the Antarctic stratosphere. Most of the carbon-14 remains behind in the Arctic stratosphere. 210Bi/ 210Pb ratios indicate aerosol residence times of only a few days at tropospheric levels and only several weeks in the lower stratosphere. Implications for the inventory and distribution of radioactive fallout are discussed. 

We have addressed several aspects of STE of ozone and the impact on tropospheric ozone levels. Using ozone observations in the upper troposphere and lower stratosphere from MOZAIC, we have examined the rdation between ozone and PV in the lower stratosphere. A distinct seasonality in the ratio between ozone and PV is evident, with a maximum in spring and minimum in fall associated with the seasonality of downward transport in the meridional circulation and of the ozone concentrations in the lower stratosphere. The ozone-PV ratio is applied in our tropospheric chemistry-climate model to improve the boundary conditions for ozone above the tropopause, to improve the representativity of simulated ozone distributions near synoptic disturbances and realistically simulate cross-tropopause ozone transports. It is expected that the results will further improve when the model is applied in a finer horizontal and vertical resolution. 

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