Discussion on Humidity
PubMed journal article The relationship between indoor and outdoor temperature , apparent temperature, relative humidity, and absolute humidit were found in. Absolute humidity (expressed as grams of water vapor per cubic meter volume RELATIONSHIP OF DEWPOINT AND RELATIVE HUMIDITY TO CLOUDS AND. Relative humidity (RH) is the ratio of the partial pressure of water vapor to the equilibrium vapor .. The enhancement factor is commonly used to correct the equilibrium vapor pressure of water vapor when empirical relationships, such as For a given dew point and its corresponding absolute humidity, the relative humidity.
Although weather conditions affect people differently, in general in the spring and summer, surface dewpoint temperatures in the 50s usually are comfortable to most people, in the 60s are somewhat uncomfortable humidand in the 70s are quite uncomfortable very humid. In the Ohio Valley including Kentuckycommon dewpoints during the summer range from the middle 60s to middle 70s.What is relative humidity?
Dewpoints as high as 80 or the lower 80s have been recorded, which is very oppressive but fortunately relatively rare. While dewpoint gives one a quick idea of moisture content in the air, relative humidity does not since the humidity is relative to the air temperature. In other words, relative humidity cannot be determined from knowing the dewpoint alone, the actual air temperature must also be known. If the air is totally saturated at a particular level e.
If the relative humidity is percent i. It simply means that the maximum amount of moisture is in the air at the particular temperature the air is at. Saturation may result in fog at the surface and clouds aloft which consist of tiny water droplets suspended in the air. Droplets grow through a process called "collision-coalescence" whereby droplets of varying sizes collide and fuse together coalesce. Ice crystal processes including deposition and aggregation also are important for particle growth.
In thunderstorms, hail also can develop.
Once the suspended precipitation particles grow to sufficient size, the air can no longer support their weight and precipitation falls from the clouds. In humid climates, thunderstorms often cause heavier rain than general wintertime rainfall since moisture content in the air typically is higher in the spring and summer, and since air usually rises at a much more rapid rate within developing thunderstorms than in general winter systems. Meteorologists are not just interested in dewpoint or absolute humidity at the surface, but aloft as well.
Precipitable water PW is a measure of the total amount of water vapor contained in a small vertical column extending from the surface to the top of the atmosphere. However, as mentioned above, the majority of moisture in the atmosphere is contained roughly within the lowest 10, feet.
Precipitable water values around or above 1 inch are common in the spring and summer east of the Rocky Mountains including Kentucky. Values of 2 inches in the summer indicate a very high moisture content in the atmosphere, typical of a tropical air mass. In general, the higher the PW, the higher the potential for very heavy rain from thunderstorms if they were to develop.
However, another very important consideration is not only the amount of ambient moisture in a particular location, but also the amount of moisture advection and convergence which provides additional moisture to an area.
If significant, these added factors help explain why rainfall totals from thunderstorms can exceed actual PW values of the air in which the storms are occurring. The movement of thunderstorms, called propagation, also is very important in determining the actual amount of rainfall in any one location.
Discussion on Humidity
The slower the movement of thunderstorms, the higher the rainfall potential in one area. In the winter, if the air temperature was 40 F and the dewpoint was also 40, what would the relative humidity be? Now, in the spring, if the air temperature was 70 and the dewpoint was 70, what would the relative humidity be?
In which situation would if feel more humid?
Relative humidity - Wikipedia
What does this tell you about relative humidity? If the air temperature was 95 F with a dewpoint of 70, would the air's relative humidity be higher or lower than if the air temperature was 70 degrees with a dewpoint of 55?
Wooden furniture can shrink, causing the paint that covers these surfaces to fracture. When the temperature is low and the relative humidity is high, evaporation of water is slow.
When relative humidity approaches percent, condensation can occur on surfaces, leading to problems with mold, corrosion, decay, and other moisture-related deterioration.
Condensation can pose a safety risk as it can promote the growth of mold and wood rot as well as possibly freezing emergency exits shut. Certain production and technical processes and treatments in factories, laboratories, hospitals, and other facilities require specific relative humidity levels to be maintained using humidifiers, dehumidifiers and associated control systems.
Vehicles[ edit ] The basic principles for buildings, above, also apply to vehicles.
In addition, there may be safety considerations. For instance, high humidity inside a vehicle can lead to problems of condensation, such as misting of windshields and shorting of electrical components.
In vehicles and pressure vessels such as pressurized airlinerssubmersibles and spacecraftthese considerations may be critical to safety, and complex environmental control systems including equipment to maintain pressure are needed.
The low humidity is a consequence of drawing in the very cold air with a low absolute humidity, which is found at airliner cruising altitudes. Subsequent warming of this air lowers its relative humidity. This causes discomfort such as sore eyes, dry skin, and drying out of mucosa, but humidifiers are not employed to raise it to comfortable mid-range levels because the volume of water required to be carried on board can be a significant weight penalty.
As airliners descend from colder altitudes into warmer air perhaps even flying through clouds a few thousand feet above the groundthe ambient relative humidity can increase dramatically. Some of this moist air is usually drawn into the pressurized aircraft cabin and into other non-pressurized areas of the aircraft and condenses on the cold aircraft skin. Liquid water can usually be seen running along the aircraft skin, both on the inside and outside of the cabin.
Because of the drastic changes in relative humidity inside the vehicle, components must be qualified to operate in those environments. Cold humid air can promote the formation of ice, which is a danger to aircraft as it affects the wing profile and increases weight. Carburetor engines have a further danger of ice forming inside the carburetor.