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Topic: Relative humidity

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	Howstuffworks "What is relative humidity and how does it affect how I feel outside?"
		Absolute humidity is the mass of water vapor divided by the mass of dry air in a volume of air at a given temperature.
		Relative humidity is the ratio of the current absolute humidity to the highest possible absolute humidity (which depends on the current air temperature).
		This doesn't mean that the relative humidity must be 100 percent in order for it to rain -- it must be 100 percent where the clouds are forming, but the relative humidity near the ground could be much less.
	science.howstuffworks.com /question651.htm (396 words)

	8(c) Atmospheric Humidity
		Mixing ratio is a measure that refers to the mass of a specific gas component relative to the mass of the remaining gaseous components for a sample of air.
		Relative humidity can be simply defined as the amount of water in the air relative to the saturation amount the air can hold at a given temperature multiplied by 100.
		Relative humidity is often determined using a sling psychrometer or a hair hygrometer.
	www.physicalgeography.net /fundamentals/8c.html (1203 words)

	About Humidity....
		A relative humidity of 50% means half the energy has been used to evaporate water from the ground, streams, lakes anywhere else it is and 50% is still available to do more evaporation.
		In terms of relative humidity, as the parcel of air is cooled, the relative humidity increases, when the relative humidity reaches 100%, you are at the dew point temperature.
		The relative humidity with a temp of 115 and a dew point of 94 is 54% this doesn't tell you as much as the dew point when you consider the table above.
	members.tripod.com /running4fun/run/humidity.html (695 words)

	Relative Humidity: indicates how moist the air is
		Relative humidity may be defined as the ratio of the water vapor density (mass per unit volume) to the saturation water vapor density, usually expressed in percent:
		Relative humidity is also approximately the ratio of the actual to the saturation vapor pressure.
		The relative humidity for air containing 10.2 mb of water vapor is simply 100% times 10.2 mb divided by the saturation vapor pressure at the actual temperature.
	ww2010.atmos.uiuc.edu /(Gh)/guides/mtr/cld/dvlp/rh.rxml (250 words)

	Relative Humidity (Site not responding. Last check: 2007-11-04)
		Relative humidity is not a measure of how much water vapor is in the air, which is absolute humidity or just called humidity.
		Relative humidity is the amount of water in the air divided by the total amount of water the air could “hold” at a certain temperature.
		When relative humidity values are high this means there is more water vapor in the air then any other gases and therefore the evaporation process is less effective because the air can not consist of anymore water vapor.
	www.personal.psu.edu /users/m/s/mss298/Meteo482/topic2.html (802 words)

	Relative Humidity
		Relative humidities of 0, 50%, and 100% mean respectively that no water vapor is present, that the air contains half as much moisture as the maximum possible, and that the air is saturated.
		The regulation of relative humidity is as important a function of a heating or of an air-conditioning system as the regulation of temperature.
		Relative humidity is water vapor density relative to saturation density.
	www.sciencebyjones.com /relative_humidity.htm (474 words)

	Relative Humidity & Temperature Dataloggers - FAQ
		Relative humidity is a difficult variable to calibrate, primarily because of its sensitivity to even minor temperature changes.
		For information on performing humidity calibrations using salt solutions, refer to ASTM Standard E104-85 "Standard Practice for Maintaining Constant Relative Humidity by Means of Aqueous Solutions".
		Relative humidity is defined as the ratio of the water vapor pressure to the saturation vapor pressure at the prevailing ambient temperature, expressed as a percentage.
	www.veriteq.com /humidity-temperature-data-loggers/dataloggers-faq.htm (1070 words)

	Weather Elements: Sometimes It's Relative: Humidity
		Relative humidity is the dimensionless ratio between the absolute humidity and the saturation absolute humidity for the ambient temperature.
		Relative humidity is usually what the media mean when they say "humidity." Relative humidity has uses in human comfort determination and many areas of biometeorology, but it can be a confusing measure because its value varies through the day with the air temperature.
		In this example, the absolute humidity is quite low in the outdoor air, but the saturation value for cold air is also low, and thus, the outdoor air is more humid, relatively speaking.
	islandnet.com /~see/weather/elements/humidity.htm (990 words)

	Relative Humidity (Site not responding. Last check: 2007-11-04)
		Relative humidity is an expression of the amount of moisture in the air compared to the total amount the air is capable of holding at that temperature and pressure.
		When the relative humidity is 60 percent or higher, a fire may leave unburned islands or may not burn hot enough to accomplish the desired result.
		The response to changes in relative humidity is much more rapid in fine dead fuels suspended above the ground than in those that have become part of the litter layer..
	www.pfmt.org /fire/relative_humidity.htm (459 words)

	About Humidity....
		Humidity refers to water vapor in the air and for years relative humidity has been what meteorologists use to inform the TV audience about how humid it is. There is much misunderstanding about humidity in general and relative humidity in particular.
		A relative humidity of 50% means half the available energy has been used to evaporate water from the ground, streams, lakes anywhere else it is and 50% is still available to do more evaporation.
		In terms of relative humidity, as the parcel of air is cooled, the relative humidity increases, when the relative humidity reaches 100%, the air parcel has cooled to the dew point temperature.
	www.shorstmeyer.com /wxfaqs/humidity/humidity.html (2044 words)

	RELATIVE HUMIDITY (Site not responding. Last check: 2007-11-04)
		Relative humidity is uniformly high and its annual mean ranges from 70% to 80%.
		The seasonal variation of relative humidity is almost conformable to the rainfall pattern of the area.
		Usually, the higher relative humidity is observed in the rainy season from May to October and the lower in the dry season from November to April.
	www.geo.mtu.edu /volcanoes/fuego/humidity.html (74 words)

	Howstuffworks "How Humidifiers Work"
		A low relative humidity means that the air is dry and could hold a lot more moisture at that temperature.
		If the relative humidity is 100 percent, we feel much hotter than the actual temperature indicates because our sweat does not evaporate at all.
		In the winter, relative humidity is often much lower than 45 percent, and in the summer it is sometimes higher.
	home.howstuffworks.com /humidifier1.htm (675 words)

	Meteorology- Online
		Humidity is a term describing the amount of water vapor or moisture being carried by air.
		Relative humidity depends not only on how much water vapour is in the air, but also on the air's temperature.
		This explains why relative humidities are higher at night, when the air is cooler, than during the day even though the amount of water vapour in the air doesn't change.
	library.thinkquest.org /C0112425/stu_rain.htm (898 words)

	How Humidity is Expressed
		Relative Humidity: we can compare how much water vapor is present in the air to how much water vapor would be in the air if the air were saturated.
		Relative humidity is a ratio that compares the amount of water vapor in the air with the amount of water vapor that would be present in the air at saturation.
		Relative humidity is given as a percentage: the amount of water vapor is expressed as a percent of saturation.
	daphne.palomar.edu /jthorngren/measures.htm (1323 words)

	Engine Tuning Calculator - relative humidity
		Relative Humidity is a measure of how much moisture is in the air compared to the amount of moisture that the air could hold at saturation.
		Relative humidity is a function of temperature and therefore changes as the temperature changes, even if the amount of moisture in the air remains constant.
		The relative air density is the ratio of the calculated air density to the air density at sea level using the ICAO standard reference conditions.
	wahiduddin.net /calc/calc_hp.htm (630 words)

	Relative Humidity: how it can affect your health and your home
		Humidity level both inside and outside your home is expressed by the term "relative humidity".
		Relative humidity is the percentage of water vapor within the air, compared to the total amount of water vapor the air is capable of absorbing.
		As an example, 50% relative humidity means that the air is holding half of the moisture it is capable of absorbing at the present temperature.
	www.autoflohumidifiers.com /relative-humidity.html (269 words)

	ICH Guidelines, Relative Humidity Conditions
		The display or recording is typically connected to one relative humidity sensor and specifically monitors the conditions at that single location in your room, chamber, or section of ductwork.
		Because relative humidity is temperature dependent, precise air temperature control is required for close relative humidity control.
		Use a relative humidity sensor suitable to your application; be sure that it is positioned properly and is calibrated routinely.
	www.humiditycontrol.com /pgc-ich.html (1608 words)

	The Weather Network · Glossary Index (Site not responding. Last check: 2007-11-04)
		Relative humidity is a percentage of water vapour per area at a specific temperature.
		Relative humidity is calculated at all times of the year, but the humidex is usually only given in the warmer months from May to September.
		Relative humidity can be calculated using various methods and instruments.
	theweathernetwork.com /inter/help/glossary/pages/relativehumidity.htm (176 words)

	NASA - Humidity Relative to Earth's Temperature
		Humidity levels in this part of the atmosphere, especially in the tropics, are important for global climate, because this is where the water vapor has the strongest impact as a greenhouse gas.
		Relative humidity relates to the saturation point, the amount of water vapor in the air divided by the maximum amount of water the air is capable of holding at a given temperature.
		Using the UARS data to actually quantify both specific humidity and relative humidity, the researchers found, while water vapor does increase with temperature in the upper troposphere, the feedback effect is not as strong as models have predicted.
	www.nasa.gov /vision/earth/lookingatearth/warmer_humidity.html (905 words)

	Relative humidity - Wikipedia, the free encyclopedia
		[1] Relative humidity is simply the ratio of the amount of water vapor in air to the maximum amount of water vapor that could be present if the vapor were at its saturation conditions.
		By comparison, a relative humidity between 40% and 60% is considered healthy and comfortable for human habitation.
		A device used to measure humidity is called a hygrometer, one used to regulate it is called a humidistat, or sometimes hygrostat.
	en.wikipedia.org /wiki/Relative_humidity (1023 words)

	GeoDetectives, Hydrology, humidity (Site not responding. Last check: 2007-11-04)
		Relative humidity is the saturation percentage of air.
		Relative Humidity (RH) is the amount of water vapor in the air relative to the maximum amount of water vapor the air can hold when completely saturated.
		The distinction is that 100% humidity can create rain, but once the rain falls from the cloud it usually enters air of much lower humidity.
	www.nps.gov /brca/Geodetect/Hydrology/humidity.htm (1006 words)

	calc_humidity
		Humidity is essentially the number of water vapour molecules in the air, but there are many and varied ways of expressing it.
		All of these terms are used scientifically, but humidity figures provided for public use in newspapers are usually relative humidity.
		Relative humidity therefore decreases with increasing temperature if the actual amount of water vapour stays the same.
	www.bom.gov.au /lam/humiditycalc.shtml (671 words)

	nbcweatherplus.com - Weather News - Relative Humidity Versus Dew Point
		The true definition of relative humidity (RH), is the ratio of the amount of water vapor actually in the air compared to the maximum amount of water vapor the air can hold at that particular temperature (and pressure).
		Air with 100 percent relative humidity is said to be saturated because it is filled to capacity with vapor.
		When the air temperature and dew point are far apart, the relative humidity is low; when they are close to the same value, the relative humidity is high.
	wmaq.nbcweatherplus.com /weathernews/1203206/detail.html (508 words)

	NSCC Publications - How temperature and relative humidity affect collection deterioration rates
		Relative humidity (RH) governs the amount of moisture contained in materials at equilibrium with the environment.
		Lowering the relative humidity from 60 percent to 20 percent, while keeping the temperature constant at 70 degrees Fahrenheit also increased film life, but less drastically, from 30 years to 90 years.
		Because of this, staff may need to ramp relative humidity between 35 percent (or lower) in the winter and 45 or 55 percent (depending on dehumidification capabilities) in the summer.
	www.collectioncare.org /pubs/v2n2p1.html (2297 words)

	relative humidity information
		The optimum relative humidity range for the well being of the home and for the health of the occupants is between 30% to 50% RH.
		Homes that have high humidity levels are more likely to become infested with termites and carpenter-ants since these insects prefer and migrate towards moist wood, and the steel components of a home may begin to rust if the indoor relative humidity is too high.
		Relative humidity is defined as the ratio of the water vapor pressure or water vapor content
	www.indoorhealthproducts.com /relative-humidity.htm (1254 words)

	Relative Humidity of Air
		Relative humidity can be expressed by partial vapor and air pressure, density of the vapor and air, or by the actual mass of the vapor and air.
		Relative humidity can be expressed as the ratio of the vapor pressure of the air - to the saturation vapor pressure of the air at the actual dry bulb temperature.
		Relative humidity can also be expressed as the ratio at actual mass of water vapor in a given air volume - to the mass of water vapor required to saturate at this volume.
	www.engineeringtoolbox.com /relative-humidity-air-d_687.html (671 words)

	Humidity
		Controlling humidity is not only important from the standpoint of comfort but also significant when it comes to maintaining healthy indoor environments.
		Studies of personal comfort have shown that relative humidity ranges between 30% and 65-70% can be considered 'comfortable' depending on activity.
		Relative humidity conditions near ground level can be much less than at cloud level; rain is leaving air that is saturated (100%RH), but is falling through air which may be at lower RH levels.
	www.envirochex.com /Humidity.htm (638 words)

	Relative Humidity (Site not responding. Last check: 2007-11-04)
		There is a very clear correlation with high values of relative humidity and areas of low pressure and also the areas of predicated precipitation.
		the higher the relative humidity is, the closer the air is to saturation and thus precipitation forms.
		Relative humidity is a measure based on the dew point temperature; we can say this because the relationship between the dew point temperature and the air’s temperature correlates very well with relative humidity.
	www.personal.psu.edu /students/d/s/dsb175/RH (1152 words)

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