Tropospheric residence times

Tropospheric residence time only shorter lifetime appUes to urban areas where NO quickly destroys O. ... 

Moore, H.E., Poet, S.E. Martell, E.A. (1972) Tropospheric residence times indicated by radon and radon daughter concentrations. In Natural Radiation Environment II, CONF-720805, ed. J.A.S. Adams, W.M. Lowder T.F. Gesell, Springfield, Va, pp. 775-85. 

Levy (155) calculated an mixing ratio of 0.7 ppm and a tropospheric residence time of 2 yr. From this agreement it appears that both the major source and the major sink for H2 are homogeneous gas-phase reactions in the troposphere. 

There is not yet a great deal of atmospheric sulfur chemistry to consider. From daily average values of n(OH) and n(H02), it is possible to estimate the lower troposphere residence times of H2S and S02 ... 

Martell, E.A. and Moore, H.E., Tropospheric residence times A critical review. J. Rech. Atmos., 8 (1974) 903-910. 

Table 4-5. Hemispheric and Average Tropospheric Residence Times and Corresponding Average OH Number Densities Obtained from the Detailed Budget of CH3CCI3 (Singh, 1977 b)...

The total flux of methane into the stratosphere, 60 Tg/yr, combines with the rate of CH4 oxidation by OH to give a total sink strength of 400 Tg/yr. This agrees approximately with the global emission estimates of Table 4-7. Although methane has been observed to increase in the troposphere, the budget must be about balanced since the increase is slow. If we take a value of 400 Tg/yr as representative for ( Ch4 ch4 the tropospheric residence time for methane is... 

As for other constituents of the atmosphere, it is possible to set up a mass budget of the aerosol and to calculate its residence time. The main problem is to characterize the global distribution of particulate matter in order to determine its total mass in the troposphere. One may then apply the emission estimates of Table 7-11 to calculate the tropospheric residence time ta with the help of Eq. (4-11). This approach will be discussed in the first part of this section. Subsequently, we consider an independent method for estimating the residence time, which results from the use of radioactive tracers. Finally, the removal of aerosol particles by sedimentation and impactation at the Earth surface will be discussed. 

Schemes that one may apply to deduce aerosol residence times from various radioactive elements have been reviewed by Junge (1963), Martell and Moore (1974), and Turekian et al. (1977). The published data admit residence times in the range 4-72 days, but crowd into two groups of values averaging 6 and 35 days, respectively. From the evidence available to him, Junge (1963) concluded that the higher value was appropriate to the troposphere as a whole and that the lower values were applicable only to the boundary layer near the Earth surface. Martell and Moore (1974), after having critically reviewed older and newer data, came to the opposite conclusion, namely, that the high values are due to the contribution of stratospheric aerosols, apart from misinterpretations of some data, while the lower values represent the true tropospheric residence time essentially independent of altitude.

For comparison with the data in Fig. 7-28, it is instructive to calculate tropospheric residence times resulting exclusively from dry deposition. We confine the calculation to the size range 0.05-1.0 xm, where the deposition velocity is roughly size-independent. For continental aerosols this size region contains approximately one-half of the total mass of all aerosol particles. The residence time is then given by the tropospheric column content of such particles divided by their flux to the ground,... 

Bandy, A. R., P. J. Maroulis, L. Shalaby, and L. A. Wilner (1981). Evidence for a short tropospheric residence time for carbon disulfide. Geophys. Res. Lett. 8, 1180-1183. 

Like methane and nitrous oxide, tropospheric ozone is a natural greenhouse gas, but one which has a short tropospheric residence time. Ozone s bending vibration occurs at 14.2 pm, near that for CO2, and thus it does not contribute much to the enhancement of the greenhouse effect since atmospheric carbon dioxide already removes much of the outgoing light in this wavelength. 

Balkanski et al. (1993) following a global three-dimensional model which uses meteorological parameters, such as precipitation scavenging, computed residence times for Pb aerosols in the tropospheric column of about 5 days at southern mid-latitudes up to 80 S and 10-15 days in the tropics (30 S-30 N). Values at northern mid-latitudes up to 80 N varied from about 5 days in winter to about 10 days in summer. The residence time of Pb produced in the lowest 0.5 km of atmosphere is on average four times shorter than that of Pb produced in the upper atmosphere. They found that the tropospheric residence time is a function of latitude according to the following equation (Ehhalt, 1973)... 

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