Water vapor
Use of water vapor, as steam, has been important for cooking, and as a major component in energy production and transport systems since the industrial revolution.
Water vapor, which reacts to temperature changes, is referred to as a 'feedback', because it amplifies the effect of forces that initially cause the warming.
In the US, the National Weather Service measures the actual rate of evaporation from a standardized "pan" open water surface outdoors, at various locations nationwide.
[8] As a result, there are large areas where millennial layers of snow have sublimed, leaving behind whatever non-volatile materials they had contained.
This is extremely valuable to certain scientific disciplines, a dramatic example being the collection of meteorites that are left exposed in unparalleled numbers and excellent states of preservation.
Typically the specimens are prepared by cryofixation and freeze-fracture, after which the broken surface is freeze-etched, being eroded by exposure to vacuum until it shows the required level of detail.
This technique can display protein molecules, organelle structures and lipid bilayers with very low degrees of distortion.
Deposition is a phase transition separate from condensation which leads to the direct formation of ice from water vapor.
Direct methods may use electronic transducers, moistened thermometers or hygroscopic materials measuring changes in physical properties or dimensions.
In very warm air (35 °C) the proportion of water vapor is large enough to give rise to the stuffiness that can be experienced in humid jungle conditions or in poorly ventilated buildings.
Energy input, such as sunlight, can trigger more evaporation on an ocean surface or more sublimation on a chunk of ice on top of a mountain.
Controlling water vapor in air is a key concern in the heating, ventilating, and air-conditioning (HVAC) industry.
The condensation of water vapor to the liquid or ice phase is responsible for clouds, rain, snow, and other precipitation, all of which count among the most significant elements of what we experience as weather.
For example, latent heat release in atmospheric convection is directly responsible for powering destructive storms such as tropical cyclones and severe thunderstorms.
Water vapor is an important greenhouse gas[18][19] owing to the presence of the hydroxyl bond which strongly absorbs in the infra-red.
Scientists thus distinguish between non-condensable (driving) and condensable (driven) greenhouse gases, i.e., the above water vapor feedback.
Under persistent condensation or deposition, cloud droplets or snowflakes form, which precipitate when they reach a critical mass.
Other sources of atmospheric water include combustion, respiration, volcanic eruptions, the transpiration of plants, and various other biological and geological processes.
[40] Episodes of surface geothermal activity, such as volcanic eruptions and geysers, release variable amounts of water vapor into the atmosphere.
However, water vapor is consistently the commonest volcanic gas; as a rule, it comprises more than 60% of total emissions during a subaerial eruption.
[48] In addition, atmospheric water will reflect and refract signals to an extent that depends on whether it is vapor, liquid or solid.
[49] A comparison of GOES-12 satellite images shows the distribution of atmospheric water vapor relative to the oceans, clouds and continents of the Earth.
The maps are based on data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on NASA's Aqua satellite.
The most noticeable pattern in the time series is the influence of seasonal temperature changes and incoming sunlight on water vapor.
In the tropics, a band of extremely humid air wobbles north and south of the equator as the seasons change.
[51] The weaker water vapor absorption lines in the blue spectral range and further into the UV up to its dissociation limit around 243 nm are mostly based on quantum mechanical calculations[52] and are only partly confirmed by experiments.
The strength of each discharge is directly related to the atmospheric permittivity, capacitance, and the source's charge generating ability.
[60] Water vapor has been found to be a major constituent of the atmosphere of dwarf planet, Ceres, largest object in the asteroid belt[61] The detection was made by using the far-infrared abilities of the Herschel Space Observatory.
Spectroscopic analysis of HD 209458 b, an extrasolar planet in the constellation Pegasus, provides the first evidence of atmospheric water vapor beyond the Solar System.
A NASA satellite designed to study chemicals in interstellar gas clouds, made the discovery with an onboard spectrometer.
