<P> The density of the Earth's atmosphere decreases nearly exponentially with altitude . The total mass of the atmosphere is M = ρ H ≃ 1 kg / cm within a column of one square centimeter above the ground (with ρ = 1.29 kg / m the atmospheric density on the ground at z = 0 m altitude, and H ≃ 8 km the average atmospheric scale height). 80% of that mass is concentrated within the troposphere . The mass of the thermosphere above about 85 km is only 0.002% of the total mass . Therefore, no significant energetic feedback from the thermosphere to the lower atmospheric regions can be expected . </P> <P> Turbulence causes the air within the lower atmospheric regions below the turbopause at about 110 km to be a mixture of gases that does not change its composition . Its mean molecular weight is 29 g / mol with molecular oxygen (O) and nitrogen (N) as the two dominant constituents . Above the turbopause, however, diffusive separation of the various constituents is significant, so that each constituent follows its own barometric height structure with a scale height inversely proportional to its molecular weight . The lighter constituents atomic oxygen (O), helium (He), and hydrogen (H) successively dominate above about 200 km altitude and vary with geographic location, time, and solar activity . The ratio N / O which is a measure of the electron density at the ionospheric F region is highly affected by these variations . These changes follow from the diffusion of the minor constituents through the major gas component during dynamic processes . </P> <P> The thermosphere contains an appreciable concentration of elemental sodium located in a 10 - km thick band that occurs at the edge of the mesosphere, 80 to 100 km above Earth's surface . The sodium has an average concentration of 400,000 atoms per cubic centimeter . This band is regularly replenished by sodium sublimating from incoming meteors . Astronomers have begun utilizing this sodium band to create "guide stars" as part of the optical correction process in producing ultra-sharp ground - based observations . </P> <P> The thermospheric temperature can be determined from density observations as well as from direct satellite measurements . The temperature vs. altitude z in Fig. 1 can be simulated by the so - called Bates profile: </P>

How does conduction increase the temperature of the air above the earth's surface