amount of air in the atmosphere
Table 1-1 lists the mixing ratios of some major atmospheric gases. The most abundant is molecular nitrogen (N2) with a mixing ratio CN2 = 0.78 mol/mol; N2 accounts for 78% of all molecules in the atmosphere. Next in abundance are molecular oxygen (O2) with CO2 = 0.21 mol/mol, and argon (Ar) with CAr = 0.0093 mol/mol. Quick Answer. The thickest layer of the atmosphere is the troposphere, which averages 11 miles high at the equator and is thinner at the poles. All the weather occurs in this layer, and the troposphere contains nearly 80 percent of the air in the Earth's atmosphere. Above the troposphere, in ascending order, is the stratosphere, mesosphere, thermosphere and exosphere. The troposphere is wider at the equator (10mi) than at the poles (5mi). The troposphere contains 75 percent of atmosphere's mass- on an average day the weight of the molecules in the air is14.7 lb..(sq. in.)- and most of the atmosphere's water vapor. Water vapor concentration varies from trace amounts in Polar Regions to nearly 4 percent in the tropics. Atmospheric Moisture. You should realize that moisture in the atmosphere can appear in three states--solid, liquid, and a gaseous vapor. It is very rare when the air does not contain some water vapor. When the air is cooled to its saturation point, condensation occurs in the form of clouds and perhaps precipitation. Clouds are, of course, the most visible manifestation of atmospheric water, but even clear air contains water—water in particles that are too small to be seen. One estimate of the volume of water in the atmosphere at any one time is about 3,100 cubic miles (mi3) or 12,900 cubic kilometers (km3). That may sound like a lot, but it is only about 0.001 percent of the total Earth's water volume of about 332,500,000 mi3 (1,385,000,000 km3), as shown in the table below. If all of the water in the atmosphere rained down at once, it would only cover the globe to a depth of 2.5 centimeters, about 1 inch. The mixing ratios in Table 1-1 are for dry air, excluding water vapor. Water vapor mixing ratios in the atmosphere are highly variable (10-6-10-2 mol/mol). This variability in water vapor is part of our everyday experience as it affects the ability of sweat to evaporate and the drying rate of clothes on a line. The 1-5% range places water vapor as the third most common gas (which alters the other percentages accordingly). This is composition of air in percent by volume, at sea level at 15 C and 101325 Pa. Nitrogen -- N2 -- 78.084%. Updated February 13, 2017. Nearly all of the Earth's atmosphere is made up of only five gases: nitrogen, oxygen, water vapor, argon, and carbon dioxide. Several other compounds also are present. Although this CRC table does not list water vapor, air can contain as much as 5% water vapor, more commonly ranging from 1-3%. First, you should understand that the temperature of the air influences the amount of water vapor that can be bound to the molecules of air. Water vapor capacity increases with temperature increase. There are three parcels of air, each in separate containers. Only relative values of moisture and temperature are shown. The troposphere is the lowest layer of Earth's atmosphere and site of all weather on Earth. The troposphere is bonded on the top by a layer of air called the tropopause, which separates the troposphere from the stratosphere, and on bottom by the surface of the Earth.
The troposphere contains nearly 80 percent of the air in the Earth's atmosphere.