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Water vapor reflects radar to a lesser extent than do water's other two phases. In the form of drops and ice crystals, water acts as a prism, which it does not do as an individual molecule; however, the existence of water vapor in the atmosphere causes the atmosphere to act as a giant prism. [49]
The amount of water that can exist as vapor in a given volume increases with the temperature. When the amount of water vapor is in equilibrium above a flat surface of water the level of vapor pressure is called saturation and the relative humidity is 100%. At this equilibrium there are equal numbers of molecules evaporating from the water as ...
Aerosol of microscopic water droplets suspended in the air above a cup of hot tea after the water vapor has sufficiently cooled and condensed. Water vapor is an invisible gas, but the clouds of condensed droplets refract and scatter the sunlight and are thus visible. Droplets of water vapor in a pan. Demonstration of evaporative cooling.
Water vapor concentration for this gas mixture is 0.4%. Water vapor is a greenhouse gas in the Earth's atmosphere, responsible for 70% of the known absorption of incoming sunlight, particularly in the infrared region, and about 60% of the atmospheric absorption of thermal radiation by the Earth known as the greenhouse effect. [25]
The concentration of water vapor (a greenhouse gas) varies significantly from around 10 ppm by mole fraction in the coldest portions of the atmosphere to as much as 5% by mole fraction in hot, humid air masses, and concentrations of other atmospheric gases are typically quoted in terms of dry air (without water vapor).
Advection: The movement of water through the atmosphere. [6] Without advection, water that evaporated over the oceans could not precipitate over land. Atmospheric rivers that move large volumes of water vapor over long distances are an example of advection. [7] Condensation: The transformation of water vapor to liquid water droplets in the air ...
It is a reflection of the energy available to evaporate or transpire water, and of the wind available to transport the water vapor from the ground up into the lower atmosphere and away from the initial location. Potential evapotranspiration is expressed in terms of a depth of water or soil moisture percentage.
Boiling is also a phase transition from the liquid phase to gas phase, but boiling is the formation of vapor as bubbles of vapor below the surface of the liquid. Boiling occurs when the equilibrium vapor pressure of the substance is greater than or equal to the atmospheric pressure. The temperature at which boiling occurs is the boiling ...