Radiative impact

Treffeisen R, Tunved P, Strom J, Herber A, Bareiss J, Helbig A, Stone RS, Hoyningen-Huene W, Krejci R, Stohl A, Neuber R (2007) Arctic smoke - aerosol characteristics during a record smoke event in the European Arctic and its radiative impact. Atmos Chem Phys 7 3035-3053... 

Lund Myhre C, Toledano C, Myhre G, Stebel K, Yttri KE, Aaltonen V, Johnsmd M, Frioud M, Cachorro V, de Frutos A, Lihavainen H, Campbell JR, Chaikovsky AP, Shiobara M, Welton EJ, Tprseth K (2007) Regional aerosol optical properties and radiative impact of the extreme smoke event in the European Arctic in spring 2006. Atmos Chem Phys 7 5899-5915... 

Stratospheric Chemistry and Radiative Impacts of Volcanic Plumes... 

Cooke W. F., Liousse C., Cachier H., and Feichter J. (1999) Construction of a 1° X 1° fossil fuel emission data set for carbonaceous aerosol and implementation and radiative impact in the ECHAM4 model. J. Geophys. Res. 104, 22137-22162. 

Lu, M. L., McClatchey, R. A., and Seinfeld, J. H. (2002) Cloud halos Numerical simulation of dynamical structure and radiative impact, J. Appl. Meteorol. 41, 832-848. 

Grini, A., G. Myhre, J. K. Sundet and I. S. A. Isaksen (2002) Modeling the annual cycle of sea salt in the global 3D model Oslo CTM2 Concentrations, fluxes, and radiative impact. Journal of Climate 15, 1717-1730... 

The relationship between heat transfer and the boundary layer species distribution should be emphasized. As vaporization occurs, chemical species are transported to the boundary layer and act to cool by transpiration. These gaseous products may undergo additional thermochemical reactions with the boundary-layer gas, further impacting heat transfer. Thus species concentrations are needed for accurate calculation of transport properties, as well as for calculations of convective heating and radiative transport. 

Atmospheric aerosols have a direct impact on earth s radiation balance, fog formation and cloud physics, and visibility degradation as well as human health effect[l]. Both natural and anthropogenic sources contribute to the formation of ambient aerosol, which are composed mostly of sulfates, nitrates and ammoniums in either pure or mixed forms[2]. These inorganic salt aerosols are hygroscopic by nature and exhibit the properties of deliquescence and efflorescence in humid air. That is, relative humidity(RH) history and chemical composition determine whether atmospheric aerosols are liquid or solid. Aerosol physical state affects climate and environmental phenomena such as radiative transfer, visibility, and heterogeneous chemistry. Here we present a mathematical model that considers the relative humidity history and chemical composition dependence of deliquescence and efflorescence for describing the dynamic and transport behavior of ambient aerosols[3]. 

Of the different kinds of forbiddenness, the spin effect is stronger than symmetry, and transitions that violate both spin and parity are strongly forbidden. There is a similar effect in electron-impact induced transitions. Taken together, they generate a great range of lifetimes of excited states by radiative transitions, 109 to 103 s. If nonradiative transitions are considered, the lifetime has an even wider range at the lower limit. 

Table 14.4 summarizes the estimated total direct radiative forcing calculated for the period from preindustrial times to 1992 for C02, CH4, N20, and O, (IPCC, 1996). The estimate for CH4 includes the effects due to its impacts on tropospheric ozone levels or on stratospheric water vapor, both of which are generated during the oxidation of methane. That shown for 03 is based on the assumption that its concentration increased from 25 to 50 ppb over the Northern Flemi-sphere. The total radiative forcing due to the increase in these four gases from preindustrial times to the present is estimated to be 2.57 W m 2. 

In short, while net radiative forcing is a convenient means for examining the potential importance of various anthropogenic perturbations for climate, it cannot be used in an additive manner for gases and aerosol particles to predict the ultimate impacts. 

If this excess absorption by clouds is ultimately shown to be a real phenomenon, then an increased cloud formation and extent due to anthropogenic emissions may alter the radiative balance of the atmosphere not only through increased reflectance but also through increased absorption of solar radiation. Such an effect could impact atmospheric temperatures, their vertical distribution, and circulation, as well as surface wind speeds and the surface latent heat flux (Kiehl et al., 1995). Hence establishing if this is truly excess absorption, and if so, its origins, is a critical issue that remains to be resolved. 

Brasseur, G. P., J. T. Kiehl, J.-F. Muller, T. Schneider, C. Granier, X. Tie, and D. Hauglustaine, Past and Future Changes in Global Tropospheric Ozone Impact on Radiative Forcing, Geophys. Res. Lett, 25, 3807-3810 (1998). 

Solomon, S., and J. S. Daniel, "Impact of the Montreal Protocol and Its Amendments on the Rate of Change of Global Radiative Forcing, Clim. Change, 32, 7-17 (1996). 

The radiative lifetime for the 52IIr state has been measured by Jeunehomme and Duncan,222 who produced the state by electron impact. For the radiative step... 

Additional details on some of these methods are described in other sections of this review. Attempts have also been made to determine excited-state populations in single-source mass-spectrometric experiments from an analysis of ionization efficiency curves.38ad There are several difficulties in applying such methods. For instance, it is now known from photoionization studies that ionization processes may be dominated by autoionization. Therefore, the onset of a new excited state is not necessarily characterized by an increased slope in the electron-impact ionization-efficiency curve, which is proportional to the probability of producing that state, as had been assumed earlier. Another problem arises because of the different radiative lifetimes that are characteristic of various excited ionic states (see Section I.A.4). 

Utilizing ionization efficiency curves to determine relative populations of vibrationally excited states (as in the photoionization experiments) is a quite valid procedure in view of the long radiative lifetime that characterizes vibrational transitions within an electronic state (several milliseconds). However, use of any ionization efficiency curve (electron impact, photon impact, or photoelectron spectroscopic) to obtain relative populations of electronically excited states requires great care. A more direct experimental determination using a procedure such as the attenuation method is to be preferred. If the latter is not feasible, accurate knowledge of the lifetimes of the states is necessary for calculation of the fraction that has decayed within the time scale of the experiment. Accurate Franck -Condon factors for the transitions from these radiating states to the various lower vibronic states are also required for calculation of the modified distribution of internal states relevant to the experiment.991 102... 

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