Atmosphere from Earth

The regions of the atmosphere, from Earth s surface outward, are the troposphere, the stratosphere, the mesosphere, the thentiosphere, and the ionosphere. 

Effect of Nitric Oxide on Ozone Depletion. Nitrous oxide is injected into the atmosphere from natural sources on earth about 10% is converted to nitric oxide (N20 + 0( D) — 2 NO), which in turn can catalyze the destmction of ozone (11,32,75). The two main cycles are 1 and 2. Rate constant data are given in Reference 11. 

Fig. 17-4. Radiation heat balance. The 100 units of incoming shortwave radiahon are distributed reflected from earth s surface to space, 5 reflected from cloud surfaces to space, 20 direct reaching earth, 24 absorbed in clouds, 4 diffuse reaching earth through clouds, 17 absorbed in atmosphere, 15 scattered to space, 9 scattered to earth, 6. The longwave radiation comes from (1) the earth radiating 119 units 101 to the atmosphere and 18 directly to space, and (2) the atmosphere radiating 105 units back to earth and 48 to space. Additional transfers from the earth s surface to the atmosphere consist of latent heat, 23 and sensible heat, 10. Source After Lowry (4).

Considerable energy is radiated back from Earth s surface into space as long-wave infrared radiation. The atmosphere absorbs some of this infrared radiation, preventing its loss to space. This trapping is sometimes referred to as the Greenhouse Effect. ... 

Measurements show that the mean OLR from Earth is 237 W m-2 (Salby, 1996). Equation (1) indicates that our planet is then in thermal equilibrium at an effective temperature of 254.2 K. This blackbody temperature of the atmosphere is the effective mean temperature of Earth and its atmosphere. It corresponds to a shell-like layer of temperature, Te, surrounding the planet at a mean altitude of approximately 6.5 km. 

One of the projects planned for the next decade is Darwin, to be organised by ESA. Darwin will be a flotilla of four or five spacecraft that will search for Earth-like planets around other stars and analyse their atmospheres for the chemical signature of life. Three of the spacecraft will carry 3 1 m space telescopes , which will form the Infrared Space Interferometer IRSI they will be stationed 1.5 million kilometres from Earth, in the opposite direction from the Sun, at the Lagrangian Point L2 (a libration point at which the gravitational forces of the Earth and the sun cancel out). 

Fig. 1.12. One hypothesis of the evolution of oxygen in the atmosphere in relation to the origin of life and the evolution of higher organisms. (From Earth (4th edn) by Press and Siever. Copyright 1986 W.H. Freeman and Company, with permission.)...

Much of the electromagnetic spectrum has been used to investigate the structure of matter in the laboratory but the atmospheric windows restrict astronomical observations from Earth. Irritating as this is for astronomers on the ground, the chemical structure of the atmosphere and the radiation that it traps is important to the origins of life on Earth. The light that does get through the atmosphere, however, when analysed with all of the tools of spectroscopy, tells the molecular story of chemistry in distant places around the Universe. 

The next most likely possibility is cometary delivery of the atmosphere but again there are some problems with the isotope ratios, this time with D/H. The cometary D/H ratios measured in methane from Halley are 31 3 x 10-5 and 29 10 x 10-5 in Hayuatake and 33 8 x 10-5 in Hale-Bopp, whereas methane measurements from Earth of the Titan atmosphere suggest a methane D/H ratio of 10 5 x 10-5, which is considerably smaller than the ratio in the comets. The methane at least in Titan s atmosphere is not exclusively from cometary sources. Degassing of the rocks from which Titan was formed could be a useful source of methane, especially as the subnebula temperature around Saturn (100 K) is somewhat cooler than that around Jupiter. This would allow volatiles to be more easily trapped on Titan and contribute to the formation of a denser atmosphere. This mechanism would, however, apply to all of Saturn s moons equally and this is not the case. 

Hydrological cycle The cyclic transfer of water vapor from the Earth s surface via evapotranspiration into the atmosphere, from the atmosphere via precipitation back to earth, and through runoff into streams, rivers, and lakes, and ultimately into the oceans (U.S. Geological Survey, 2003). 

Cosmic rays Protons and a particles that enter Earth s atmosphere from outer space. When they collide with atoms or molecules of atmospheric gas, high-energy neutrons can be given off These neutrons can then undergo nuclear reactions with other atmospheric gas atoms and molecules. 

---