Atmosphere physical profile

Under neutral conditions the atmospheric lapse rate is adiabatic. Close to the ground the vertical eddy diffusivity profile can be based on Monin-Obukhov similarity theory, in which case = 1 and = ku,z- With this formulation, increases without limit—clearly a physically unrealistic situation. Myrup and Ranzieri (1976) proposed a set of empirical roll off functions for altitudes above the surface layer ... 

Shapes or profiles of spectral lines are often very important for obtaining information about the physical system under observation. Thus a spectral profile can tell us the state of a stellar atmosphere, or it can be used as diagnostic for a plasma. The line shape of an NMR spectrum may disclose the internal motion of nuclei in a molecular system. The information thus obtained is admittedly not extremely detailed, but it may be very useful particularly when combined with other information, and often it is the only data available. 

A model atmosphere code that accounts for the special physical conditions in Wolf-Rayet atmospheres (Hamann and Schmutz, 1986 Wessolowski et al., 1987) is used to analyse the spectrum of the Wolf-Rayet star HD193077 (WN5+abs). The stellar parameters are determined such that the profiles of the helium lines He I 4471, 5876, He II >5412, and the absolute visual magnitude are reproduced. 

To obtain the concentration profiles in an atmosphere, it is important to know the time required to attain the equilibrium concentration. If the equilibrium time scale is more than a year, physical transport processes become appreciable and a large departure from the equilibrium profile is expected. The equilibrium time scale xeq may be obtained from... 

Physical transport processes and mixing ratio. The concentration profile of a minor constituent in an atmosphere is often expressed as a mixing ratio by volume or a mole fraction rather than the concentration by atmospheric modelers. Physical transport processes involve vertical and horizontal mixing by turbulence and molecular diffusion. The molecular diffusion process can be ignored in the stratosphere since it is important only above about 40 km. 

Fig. 1. Powder x-ray profiles of solid Ceo at atmospheric pressure (top) and 1.2-GPa hydrostatic pressure (bottom). Dots are experimental points (approximately 70 per point), and the solid curves are least-squares fits to an fee structurewith adjustable lattice constant a. The fitted relative intensities have no physical significance in this simple model. The scattered wave vector Q = 4TTsin6/X, where 0 is the Bragg angle for these profiles wavelength = 0.71 A. Indexing of the strongest peaks is indicated. The high-Q shoulder on the (311) is the weak (222) reflection the low-Q shoulder on the (111), observed to some extent in all our nominally pure Cfio samples, is presently unidentified. The variable intensity of this shoulder has litde eflfect on the lattice constant of a particular sample, so we can safely conclude that it has no effect on the compressibility derived from the present data.

Paterson WSB (1994) The Physics of Glaciers. Third edn. Pergamon, Oxford Univ Press, Oxford, UK Paterson WSB, Clarke GKC (1978) Comparison of theoretical and observed temperature profiles in Devon Island ice cap, Canada. Geophys J Royal Astronomical Soc 55 615-632 Petit JR and 18 others (1999) Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature 399 429-436... 

The collision rate is initially extremely fast (actually it starts at infinity) but for t 4Rp/nD, it approaches a steady-state value of /coi = 8nRp DNq. Physically, at t — 0, other particles in the vicinity of the absorbing one collide with it, immediately resulting in a mathematically infinite collision rate. However, these particles are soon absorbed by the stationary particle and the concentration profile around our particle relaxes to its steady-state profile with a steady-state collision rate. One can easily calculate, given the Brownian diffusivities in Table 9.5, that such a system reaches steady state in 10-4 s for particles of diameter 0.1 pm and in roughly 0.1 s for 1 pm particles. Therefore neglecting the transition to this steady state is a good assumption for atmospheric applications. 

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