When air is saturated, air cannot hold more water vapor and start to condense as liquid water. Water vapor regulates air temperature because it absorbs solar radiation. Water vapor: We know that water present in oceans and rivers evaporates during summer and escapes into the air. We call that saturated state is gained by the system. The maximum saturation pressure of the water vapor in moist air varies with the temperature of the air vapor mixture and can be expressed as: p ws = e (77.3450 + 0.0057 T - 7235 / T) / T 8.2 (1) where Temperature controls the amount of water in the atmosphere. Thus water vapor is one of the components of the air. This variation results due to influences from temperature, altitude, and availability of water to evaporate into the air. A percentage of water exists in the air as water vapors (in the gaseous state). Water vapor is almost always present in the surrounding air. It occupies very less percentage of earth’s atmosphere. Saturation Pressure of Water Vapor. As temperature increases, then an increasing amount of liquid or solid water can vaporize into the air. This comes directly from the definition of relative humidity, and is not some mystereous property of water. Water Vapor (Variable) Water vapor has been removed from the 100% total because of its region variability. Relative humidity measures the amount of water vapor relative to the maximum water vapor possible at that temperature. At saturation, 100% relative humidity, condensation occurs. Now, air holds the maximum amount of water vapor. Water vapor accounts for roughly 0.25% of the atmosphere by mass. After sometime, increment of water amount in the tank stops and comes to a constant value. With time, water amount in the tank increases. For example, it can make up 5% by volume in hot regions but much less in colder regions. The percentage of water vapor within the Earth's atmosphere can be as high as 4 percent. But in can make up large portions of the atmosphere. Water vapor is known as a variable gas which means its percent abundance in the air at any one place in the troposphere is not constant. humidity, percentage of water vapor in air: relative humidity (about a molecule) having a head end that attracts water and a tail end that repels it, hydrophilic at one end and hydrophobic at the other (Chemistry) amphipathic (about hemp or flax fibers) soften by soaking in water, prepare by dampening with water, soak plant fibers: ret If you would try you would notice that it doesn’t burn in absence of air. The concentration of water vapor (a greenhouse gas) varies significantly from around 10 ppm by volume in the coldest portions of the atmosphere to as much as 5% by volume in hot, humid air masses, and concentrations of other atmospheric gases are typically quoted in terms of dry air (without water vapor). Oxygen: Have you ever tried to burn a candle in absence of air? The percentage of water vapor in air ranges from 0.2% to 4%. For a given relative humidity, the total amount of water in the air does not change with pressure, but the quantity of the remaining components (mostly nitrogen and oxygen) will change.