Stratosphere chemical reactions

Why temperatures and rainfall near Chesapeake Bay should be affected by variations of the tidal forces is not so clear. However the atmosphere and stratosphere are pulled away from the earth by tidal forces just as are the waters of the earth. These forces vary by as much as 10 percent during the tidal periods [67] resulting in density variations in the stratosphere with the same periods the consequent density variations may affect the relative rates of stratospheric chemical reactions, causing disturbances of temperature and rainfall on the ground with the tidal periodicities. 

The model tropopause is defined by a PV level of 3.5 pvu poleward of 20° latitude, and by a -2 K km 1 temperature lapse rate equatorward of 20° latitude. Consequently, in this study the troposphere is defined as the volume between the surface and the simulated tropopause. Because the model does not consider typical stratospheric chemical reactions explicitly, ozone concentrations are prescribed from 1-2 levels above the model tropopause up to the top of the model domain at 10 hPa. In both hemispheres we apply monthly and zonally averaged distributions from a 2D stratospheric chemistry model [31]. In the present version of the model, we use the simulated PV and the regression analysis of the MOZAIC data (Section 2) to prescribe ozone in the NH extratropical lower stratosphere, which improves the representation of ozone distributions influenced by synoptic scale disturbances [32, 33]. Furthermore, the present model contains updated reaction rates and photodissociation data [34]. 

What are the principal chemical reactions that take place in the chemosphere to give it its name How do they influence stratospheric and tropospheric chemical reactions ... 

The atmospheric chemistry of nitrogen is quite complex and involves literally hundreds or thousands of chemical reactions. Although the fluxes are much smaller than the biological fluxes, these processes are important for a variety of reasons, including impacts on climate, stratospheric ozone, and photochemical smog. In this section we present an overview of the most important processes. 

Possibilities exist for the involvement of halo-genated species such as CCI2F2 (CFC-12) or CCI3F (CFC-11) inasmuch as they can influence the column amounts of stratospheric O3 which is both a strong absorber of solar ultraviolet radiation and an absorber and emitter of infrared radiation. (Refer back to Fig. 7-11 for a survey of the chemical reactions that are involved.)... 

Liquid interfaces are widely found in nature as a substrate for chemical reactions. This is rather obvious in biology, but even in the diluted stratospheric conditions, many reactions occur at interfaces like the surface of ice crystallites. The number of techniques available to carry out these studies is, however, limited and this is particularly true in optics, since linear optical methods do not possess the ultimate molecular resolution. This resolution is inherent to nonlinear optical processes of even order. For liquid-liquid systems, optics turns out to be rather powerful owing to the possibility of nondestructive y investigating buried interfaces. Furthermore, it appears that planar interfaces are not the only config-... 

It is not difficult to see that ozone initially forms from the oxygen present in the air. Chapman [115] introduced the photochemical model of stratospheric ozone and suggested that the ozone mechanism depended on two photochemical and two chemical reactions ... 

One of the first chemical reactions for which SIKIE was identified was the association reaction of Oj and O to produce ozone. The initial key observation was that stratospheric ozone was enriched in 0 at levels up to 40% above natural abundance. Following laboratory experiments, which showed that the enhancement occurred independently of isotopic mass (i.e., " O3 and were equivalently... 

Abstract Heterogeneous chemical reactions at the surface of ice and other stratospheric aerosols are now appreciated to play a critical role in atmospheric ozone depletion. A brief summary of our theoretical work on the reaction of chlorine nitrate and hydrogen chloride on ice is given to highlight the characteristics of such heterogeneous mechanisms and to emphasize the special challenges involved in the realistic theoretical treatment of such reactions. 

The discovery of the Ozone Hole in the Antarctic stratosphere has led to the realization that previously unsuspected heterogeneous chemical reactions occuring on the surface of ice and other stratospheric cloud particles play a critical role in atmospheric ozone depletion — not only in the Antarctic stratosphere,... 

During the dark, polar winter the temperature drops to extremely low values, on the order of-80°C. At these temperatures, water and nitric acid form polar stratospheric clouds. Polar stratospheric clouds are important because chemical reactions in the stratosphere are catalyzed on the surface of the crystals forming these clouds. The chemical primarily responsible for ozone depletion is chlorine. Most of the chlorine in the stratosphere is contained in the compounds hydrogen chloride, HCl, or chlorine nitrate, CIONO. Hydrogen chloride and chlorine nitrate undergo a number of reactions on the surface of the crystals of polar stratospheric clouds. Two important reactions are ... 

A current review of the existing and projected chemical reactions in the stratosphere was given by Tang and co-workers (Tang et al., 1998). 

Subsequent studies have shown that the cold, still, sunless Antarctic winter favors the formation of stratospheric ice crystals, and airborne compounds containing chlorine atoms then accumulate on the crystals. Chemical reactions on and within the crystals lead to the formation of Cl2. In September,... 

Notice how the temperature of the atmosphere changes with altitude. Close to the surface of the Earth, the temperature is about 20°C. The temperature falls to about — 55°C at 15 km and then rises again at higher altitudes. One reason that the stratosphere is warmer than lower regions of the atmosphere is the fact that solar radiation causes different chemical reactions at different altitudes. For example, these reactions result in a relatively stable concentration of ozone we call the ozone layer in the stratosphere. The reactions that produce ozone also release energy and, as a result, the temperature rises with altitude. 

High-altitude planes, balloons, and satellites are now studying chemical reactions in stratospheric... 

It has been known for about 50 years4 that the annual variations in ozone do not correspond to these of the solar radiation depending on the latitude and the season. The behavior of ozone is characterized by a maximum in spring and a minimum in autumn also there is more ozone at high than at low latitudes. This behavior shows that the chemical reactions in question are slow, in comparison with transport phenomena, in the lower stratosphere below 25 km. 

Thus, when studying atmospheric chemistry, it is necessary always to take into account the vertical and horizontal movements in the atmosphere, as well as the conditions controlling those chemical reactions that do not spontaneously lead to photochemical equilibrium. These conditions are applicable not only to ozone in the lower stratosphere, but also to atomic oxygen in the upper mesosphere above 75 km. In fact, equation (4) shows that, with increasing height, the formation of O3 becomes less and less important because of the decrease in the concentration of 02 and N2. Above 60 km the concentration of atomic oxygen exceeds that of ozone, but it is still in photochemical equilibrium up to 70 km. However, at the mesospause (85 km), it is subject to atmospheric movements, and its local concentration depends more on transport than on the rate of production. 

There are several mechanisms whereby organic compounds released into the atmosphere may be removed (i) physical removal by precipitation ( rain-out ) (ii) chemical reaction in the troposphere (in) transport into the stratosphere (iv) chemical reaction in the stratosphere. The physical and dynamic conditions of the different atmospheric regions will usually dictate the type of mechanism that occurs2,3. 

Stratospheric ozone Emission of ozone-depleting compounds (CFCs, Halons) Chemical reaction release of C1 and Br in stratosphere Catalytic destruction of ozone in stratosphere Skin and crop damage, damage to materials Ozone Depletion Potential (ODP)... 

Heterogeneous photochemical processes are concerned with the effect of light on interacting molecules and solid surfaces. The concept of photoinduced surface chemistry is commonly used to integrate these processes. As cited earlier, they involve surface phenomena such as adsorption, diffusion, chemical reaction and desorption [3]. Experiments and theoretical calculations make clear that the photochemical behavior of an adsorbed molecule can be very different from that of a molecule in the gas or liquid phase [4]. Photochemical reactions of this type involve molecules and systems of quite different complexity, from species composed of a few atoms in the stratosphere to large chiral organic molecules that presumably were formed in prebiotic systems. 

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