Temperature in the Lower Atmosphere

The layers of the atmosphere can be classified in a number of ways, such as by temperature, density, and chemical composition. From the standpoint of the dispersion of air pollutants, the most important classification is on the basis of temperature. 

The variation of temperature with height for a rising parcel of dry air that cools adiabat-ically, that is, with no exchange of heat with its surroundings, is a basic property of the atmosphere. We now will derive the relation for this temperature change, as it will serve as a reference temperature profile against which to compare all actual profiles. To obtain the desired relation we need only the ideal gas law and the first law of thermodynamics. 

Our intent is to apply the first law of thermodynamics to an air parcel whose volume is changing as it either ascends or descends in the atmosphere. Ultimately we will combine our result with (1.3), and so it is more convenient to work with pressure and temperature as the variables rather than with pressure and volume. Thus we convert pdV to a. form involving p and T. To do this, we express the ideal gas law as pV = mRT/M. r for a mass m of air. Then 

Using this result, together with the adiabatic condition of dQ = 0, the first law of thermodynamics reduces to 

If the air contains water vapor, the heat capacity Cp must be corrected. If Wy is the ratio of the mass of water vapor to the mass of dry air in a given volume of air, the corrected Cp  

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Equations (16.14), (16.18), and (16.22) govern the fluid velocity and temperature in the lower atmosphere. Although these equations are at all times valid, their solution is impeded by the fact that atmospheric flow is turbulent (as opposed to laminar). It is difficult to define turbulence instead we can cite a number of the characteristics of turbulent flows. Turbulent flows are irregular and random, so that the velocity components at any location vary randomly with time. Since the velocities are random variables, their exact values can never be predicted precisely. Thus (16.14), (16.18), and (16.22) become partial differential equations whose dependent variables are random functions. We cannot therefore expect to solve any of these equations exactly rather, we must be content to determine some convenient statistical properties of the velocities and temperature. The random fluctuations in the velocities result in rates of momentum, heat, and mass transfer in turbulence that are many orders of magnitude greater than the corresponding rates due to pure molecular transport. 

The contours are not exactly east-west, and thus average winds are not everywhere exactly from the west but have small components from the north or south. Such deviations from a strict westerly flow are associated with east-west variations of temperature in the lower atmosphere. Above 3 km, isotherms are generally approximately parallel to the contours. 

Water vapor pressure or the dew point temperature in the lower atmosphere usually changes very little within 24 hours. Decisive for photo-degradation is, above all, the relative humidity in the interfacial climate at the irradiated surface. Because nights are cooler than days, relative humidity is higher at night than during daytime. Due to radiant warming on the surface by day, relative humidity often decreases to values below 10% relative humidity [87]. 

Taylor and Marsh (7) investigated the long-term characteristics of temperature inversions and mixed layers in the lower atmosphere to produce an inversion climatology for the Los Angeles basin. In this area the cooler ocean currents produce an elevated inversion that is nearly always present and traps the pollutants released over the area within a layer seldom deeper than 1200 m and frequently much shallower. 

Uranus The temperature in the Uranus atmosphere, which consists of molecular hydrogen containing around 12% helium, is close to 60 K. A methane cloud layer has been detected in the lower layers of this atmosphere. The planet is surrounded by a magnetosphere which extends into space for about ten times the diameter of Uranus. The planet has 27 moons of various sizes and is surrounded by a ring system which consists of thin dark rings. The planet is unusual in two respects its tilted axis and retrograde rotation. 

In summary, large variations in the pressure, composition and temperature exist in the atmosphere, the greatest variations occurring in the lower atmospheric regions which, as will be seen, are reflected by the much more complex chemistry occurring in these regions, a chemistry which is thought to be dominated by the minor neutral constituents, doubtlessly some of which have yet to be identified. 

Although this is not a realistic situation, it is useful to know what the volume (in L) of the Earth s atmosphere would be if it were all at 1 atm pressure and at 15°C (which is the average temperature of the lower atmosphere). 

In the lower atmosphere NO is produced in any high-temperature combustion process where N2 is present. The reaction... 

The global system that regulates the earths temperature is very complex, but many scientists believe the increase in temperature is caused by an increase of certain gases in the atmosphere that trap energy that would otherwise escape into space. These gases, called greenhouse gases, include carbon dioxide, methane, nitrous oxide, chlorofluorocarbons (CFCs), and the ozone in the lower atmosphere. 

The previous discussion is based on the assumption that collisional excitation and de-excitation is the dominant process determining the populations of the vibrational-rotational levels of all radiatively active molecules. This is usually the case in the lower atmosphere, where the pressure is high and molecular collisions are frequent. The relative populations of the upper and lower states of a vibrational-rotational transition are then described by the Boltzmann distribution at the local kinetic temperature T, the gas is considered to be in local thermodynamic equilibrium (LTE), and Kirchoff s law can be applied locally. If we consider a two-level system, then the relative populations of the lower and upper states, no and ni, respectively, are given by... 

We have proposed a novel method, a periodic pulse reaction technique, to accelerate sintering under reaction conditions for the rapid estimation of catalyst life (refs. l,2j. Although the sintering is frequently accelerated by thermal treatment, the sintering behavior in the reaction atmosphere may be different from thermal sintering (ref. 3), and, furthermore, the sintering sometimes proceeds at much lower temperature in the reaction atmosphere. Thus, for the rapid estimation of catalyst life, h is necessary 10 accelerate the sintering under reaction conditions. 

Because of their short lifetimes at room temperature, the peroxy nitrates have been assumed not to act as key storage modes for peroxy radicals and NO2 in the lower atmosphere. At middle latitudes in the wintertime these may have hfetimes that approach days. Further, like the PANs these might be reformed to actively transport NO2 and peroxy radicals over long distances, depending upon the NO, hydroperoxy radical, and NO2 concentrations. With the possible exception of very cold air masses, these compounds are typically not present in significant concentrations in the troposphere because of rapid thermal decomposition to form NO2 and RO2. At room temperature they would be lost in samphng lines or during analysis. 

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