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An atmosphere (from Ancient Greek ἀτμός (atmós) 'vapour, steam' and σφαῖρα (sphaîra) 'sphere') [1] is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low.
Total atmospheric mass is 5.1480 × 10 18 kg (1.13494 × 10 19 lb), [36] about 2.5% less than would be inferred from the average sea-level pressure and Earth's area of 51007.2 megahectares, this portion being displaced by Earth's mountainous terrain. Atmospheric pressure is the total weight of the air above unit area at the point where the ...
Within the atmospheric sciences, atmospheric physics is the application of physics to the study of the atmosphere.Atmospheric physicists attempt to model Earth's atmosphere and the atmospheres of the other planets using fluid flow equations, radiation budget, and energy transfer processes in the atmosphere (as well as how these tie into boundary systems such as the oceans).
Diagram showing displacement of the Sun's image at sunrise and sunset Comparison of inferior and superior mirages due to differing air refractive indices, n. Atmospheric refraction is the deviation of light or other electromagnetic wave from a straight line as it passes through the atmosphere due to the variation in air density as a function of height. [1]
Atmospheric physics is the application of physics to the study of the atmosphere. Atmospheric physicists attempt to model Earth's atmosphere and the atmospheres of the other planets using fluid flow equations, chemical models, radiation balancing, and energy transfer processes in the atmosphere and underlying oceans and land.
The Earth's atmospheric circulation varies from year to year, but the large-scale structure of its circulation remains fairly constant. The smaller-scale weather systems – mid-latitude depressions , or tropical convective cells – occur chaotically, and long-range weather predictions of those cannot be made beyond ten days in practice, or a ...
The homosphere is the layer of an atmosphere where the bulk gases are homogeneously mixed due to turbulent mixing or eddy diffusion. The bulk composition of the air is mostly uniform so the concentrations of molecules are the same throughout the homosphere. The top of the homosphere is called the homopause, also known as the turbopause.
Objects entering an atmosphere from space at high velocities relative to the atmosphere will cause very high levels of heating. Atmospheric entry heating comes principally from two sources: convection of hot gas flow past the surface of the body and catalytic chemical recombination reactions between the surface and atmospheric gases; and