Search results
Results from the WOW.Com Content Network
Humidity affects the energy budget and thereby influences temperatures in two major ways. First, water vapor in the atmosphere contains "latent" energy. During transpiration or evaporation, this latent heat is removed from surface liquid, cooling the Earth's surface. This is the biggest non-radiative cooling effect at the surface.
2) Decreased relative humidity outside the leaf will increase the water potential gradient. Relative humidity: Drier surroundings give a steeper water potential gradient, and so increase the rate of transpiration. Wind: In still air, water lost due to transpiration can accumulate in the form of vapor close to the leaf surface.
Humidity is the amount of water vapor in the air. The vapor content of air is measured with devices known as hygrometers. The measurements are usually expressed as specific humidity or percent relative humidity. The temperatures of the atmosphere and the water surface determine the equilibrium vapor pressure; 100% relative humidity occurs when ...
Transpiration from plants is another typical source of water vapor. [25] Lastly, cool or dry air moving over warmer water will become more humid. As with daytime heating, the addition of moisture to the air increases its heat content and instability and helps set into motion those processes that lead to the formation of cloud or fog. [26]
If all the other factors influencing humidity remain constant, at ground level the relative humidity rises as the temperature falls; this is because less vapor is needed to saturate the air. In normal conditions, the dew point temperature will not be greater than the air temperature, since relative humidity typically [5] does not exceed 100%. [6]
Transpiration is a larger component of evapotranspiration (relative to evaporation) in vegetation-abundant areas. [14] As a result, denser vegetation, like forests, may increase evapotranspiration and reduce water yield. Two exceptions to this are cloud forests and rainforests. In cloud forests, trees collect the liquid water in fog or low ...
Osmotic absorption becomes more important during times of low water transpiration caused by lower temperatures (for example at night) or high humidity, and the reverse occurs under high temperature or low humidity. It is these processes that cause guttation and wilting, respectively. [66] [67] Root extension is vital for plant survival.
When the two tendencies are in balance— and the air and food are stable—the air's relative humidity (expressed as a fraction instead of as a percentage) is taken to be the water activity, a w. Thus, water activity is the thermodynamic activity of water as solvent and the relative humidity of the surrounding air at equilibrium.