Relative humidities, maximum possible

Changes in such physical factors as light, temperature (particularly maximums and minimums), relative humidity, and wind speed in forest communities subject to structural alteration by mortality of susceptible species could change the suitability of some sites for growth, reproduction, and re-establishment of survivor species. We can only speculate on some of the possible secondary effects until more data are gathered. ... 

The drying capacity of the air depends upon the relative humidity (RH) of the incoming air. At 100% RH, the air is holding the maximum amount of water possible at a given temperature, but if the temperature of the air is raised, the relative humidity drops and the air can hold more moisture. If air is saturated with water vapor at a given temperature, a drop in temperature will force the air mass to relinquish some of its moisture... 

Water concentration is also reported as humidity (absolute or relative) relative humidity is expressed by the fraction of specific humidity to the maximum specific humidity possible for a given pressure and temperature. The main sources of atmospheric gases are further explained in the text. 

The vapor pressure at equilibrium depends on the temperature and the solution, but it is independent of the relative or absolute amounts of liquid and vapor. When air adjacent to pure water is saturated with water vapor (100% relative humidity), the gas phase has the maximum water vapor pressure possible at that temperature — unless it is supersaturated, a metastable, nonequilibrium situation. This saturation vapor pressure in equilibrium with pure water (P ) increases markedly with temperature (Fig. 2-16) for example, it increases from 0.61 kPa at 0°C to 2.34 kPa at 20°C to 7.38 kPa at 40°C (see Appendix I). Thus, heating air at constant pressure and constant water content causes the relative humidity to drop dramatically, where... 

If measurements are made at atmospheric pressure the maximum relative humidities that can be attained decrease with increasing temperature (Figure 10). The maximum relative humidity possible at any temperature is equivalent to the ratio of the prevailing atmospheric pressure to the vapor pressure of water at that temperature, expressed in percent. The practice of drying lumber at high temperatures (above 100 °C) has created a renewed interest in the sorption isotherms of wood at these temperatures (23). 

Figure 10, Maximum possible relative humidities at atmospheric pressure ana temperatures above 100 °C (23).

The moisture content of the air is not a discrete system in itself. The amount of water vapor in the air is intricately linked to the temperature of the environment. Therefore, in order to get a proper perspective on the water-wood interaction, it is important to understand the relationship between temperature and relative humidity (RH). RH is a measure of how much water vapor is in the environment relative to the maximum amount of water vapor that the air could possibly hold (saturation) at a certain temperature. 

Relative humidity—ratio of the specific humidity to the maximum specific humidity possible at a given temperature and pressure (dimensionless). (See Section 1.7.)... 

The amount of moisture in the air at any time. It can be expressed in two ways the relative humidity, which is the humidity expressed as a percentage of the maximum amount of moisture it is possible for air to contain at the particular temperature and pressure of measurement. The absolute humidity is expressed as the weight of moisture in a unit volume of air. The latter is probably the more significant as regards the amount of hydrogen likely to be introduced from the atmosphere into a weld pool during welding. 

The C-curve isotherm is characterized by an initial slope that remains independent of the concentration of a substance in the soil solution until the maximum possible adsorption. This kind of isotherm can be produced either by a constant partitioning of a substance between the interfacial region and an external solution or by a proportional increase in the amount of adsorbing surface as the surface excess of an absorbate increases. The example of parathion (diethyl p-nitrophenyl monothiophosphate) adsorption in Fig. 4.1 shows constant partitioning of this compound between hexane and the layers of water on a soil at 50 per cent relative humidity. The adsorption of amino acids by Ca-montmorillonite also exhibits a... 

Special note must be made of the presence of water vapor, as it presents an often-overlooked factor. The amount of water a gas mixture is capable of containing is limited by the availability of water and the temperature of the mixture. The relative humidity measures the percentage of this upper limit actually achieved. The relationship between temperature and the maximum possible partial pressure of water has been determined empirically one suitable equation over common temperature ranges is... 

Some researchers (Stocker, 1927) feel that water vapor is of small importance for lichens and consider that they need liquid water for their assimilation activity. A conclusive answer to this question was given by precise and convincing laboratory and field experiments carried out by Lange and Bertsch (1965), Bertsch (1966), and Lange (1969). It was found that as a result of water-vapor absorption, air-dried thalli in a latent state could become reactivated and reach almost optimum photosynthesis. In Lange s (1969) experiments, dry thalli of Ramalina maciformis from the Negev desert placed in an atmosphere close to saturation were reactivated in 6-8 hours and reached photosynthetic levels that were 90% of the maximum possible value. Reactivation occurred not only in the saturated atmosphere but also in anonsaturated atmosphere with a relative air humidity of about 80-85%. The net photosynthesis of R. maciformis in an atmosphere with a relative humidity of 90% was one-fourth of the maximum value. No other form of plant life has this ability. 

Relative humidity - The ratio (in percent) of the water vapor content in the air to the maximum content possible at that temperature and pressure. 

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