Humidity,Dew Point


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Humidity,Dew Point

  1. 1. ContentsArticles Dew point 1 Humidity 5References Article Sources and Contributors 11 Image Sources, Licenses and Contributors 12Article Licenses License 13
  2. 2. Dew point 1 Dew point The dew point is the temperature where the water vapor in a volume of humid air at a constant barometric pressure will condense into liquid water. Condensed water is called dew when it forms on a solid surface. The dew point is a water-to-air saturation temperature. The dew point is associated with relative humidity. A high relative humidity indicates that the dew point is closer to the current air temperature. Relative humidity of 100% indicates the dew point is equal to the current temperature and that the air is maximally saturated with water. When the dew point remains constant and temperature increases, relative humidity decreases.[1] General aviation pilots use dew-point data to calculate the likelihood of carburetor icing and fog, and to estimate the height of the cloud base. At a given temperature but independent of barometric pressure, the dew point is a consequence of the absolute humidity, the mass of water per unit volume of air. If both the temperature and pressure rise, however, the dew point will rise and the relative humidity will lower accordingly. Reducing the absolute humidity without changing other variables will bring the dew point back down to its initial value. In the same way, increasing the absolute humidity after a temperature drop brings the dew point back down to its initial level. If the temperature rises in conditions of constant pressure, then the dew point will remain constant but the relative humidity will drop. For this reason, the same relative humidity on a day when its 80°F, and on a day when its 100°F will imply that a higher fraction of the air on the This graph shows the maximum percentage, by mass, of water vapor that air at hotter day consists of water vapor than on sea-level across a range of temperatures can contain. The behavior of water vapor the cooler day, i.e., the dew point is higher. does not depend on the presence of other gases in air. The formation of dew would occur at the dew point if water vapor were the only gas present. At a given barometric pressure but independent of temperature, the dew point indicates the mole fraction of water vapor in the air, or, put differently, determines the specific humidity of the air. If the pressure rises without changing this mole fraction, the dew point will rise accordingly; Reducing the mole fraction, i.e., making the air less humid, would bring the dew point back down to its initial value. In the same way, increasing the mole fraction after a pressure drop brings the relative humidity back up to its initial level. Considering New York (33 ft elevation) and Denver (5,130 ft elevation), for example, this means that if the dew point and temperature in both cities are the same, then the mass of water vapor per cubic meter of air will be the same, but the mole fraction of water vapor in the air will be greater in Denver.
  3. 3. Dew point 2 Relationship to human comfort When the air temperature is high, the bodys thermoregulation uses evaporation of perspiration (sweat) to cool down, with the cooling effect directly related to how fast the perspiration evaporates. The rate at which perspiration can evaporate depends on how much moisture is in the air and how much moisture the air can hold. If the air is already saturated with moisture, perspiration will not evaporate. The bodys cooling system will produce perspiration in an effort to keep the body at its normal temperature even when the rate it is producing sweat exceeds the evaporation rate. So even without generating additional body heat by exercising, one can become coated with sweat on humid days. It is the unevaporated sweat that tends to make one feel uncomfortable in humid weather. The air that affects comfort is not the air where the thermometer and humidity meters are located. It is the air that is touching ones body. As that portion of air is warmed by body heat, it will rise and be replaced with other air. If air is moved away from ones body with a natural breeze or a fan, sweat will evaporate faster, making perspiration more effective at cooling the body. The more unevaporated perspiration, the greater the discomfort. A wet bulb thermometer also uses evaporative cooling, so it provides a good analog for use in evaluating comfort level. Discomfort also exists when the dew point is low (below around −30 °C (−unknown operator: ustrong °F)). The drier air can cause skin to crack and become irritated more easily. It will also dry out the respiratory paths. OSHA recommends indoor air be maintained at 68 to 76°F (20 to 24.5°C) with a 20-60% relative humidity (a dew point of 24 to 60°F).[2] Lower dew points, less than 10 °C (unknown operator: ustrong °F), correlate with lower ambient temperatures and the body requires less cooling. A lower dew point can go along with a high temperature only at extremely low relative humidity (see graph below), allowing for relative effective cooling. Those accustomed to continental climates often begin to feel uncomfortable when the dew point reaches between 15 and 20 °C (59 and 68 °F). Most inhabitants of these areas will consider dew points above 21 °C (unknown operator: ustrong °F) oppressive. Dew point °C Dew point °F [1] Rel. humidity at 32 °C (unknown operator: Human perception ustrong °F) > Higher than 26 > Higher than 80 Severely high. Even deadly for asthma related 65% and higher °C °F illnesses 24–26 °C 75–80 °F Extremely uncomfortable, fairly oppressive 62% 21–24 °C 70–74 °F Very humid, quite uncomfortable 52–60% 18–21 °C 65–69 °F Somewhat uncomfortable for most people at upper 44–52% edge 16–18 °C 60–64 °F OK for most, but all perceive the humidity at upper 37–46% edge 13–16 °C 55–59 °F Comfortable 38–41% 10–12 °C 50–54 °F Very comfortable 31–37% < 10 °C < 49 °F A bit dry for some 30%
  4. 4. Dew point 3 Measurement Devices called dew point meters are used to measure dew point over a wide range of temperatures. These devices consist of a polished metal mirror which is cooled as air is passed over it. The temperature at which dew forms is, by definition, the dew point. Manual devices of this sort can be used to calibrate other types of humidity sensors, and automatic sensors may be used in a control loop with a humidifier or dehumidifier to control the dew point of the air in a building or in a smaller space for a manufacturing process. Calculating the dew point A well-known approximation used to calculate the dew point Td given the relative humidity RH in percent and the actual temperature T of air is: where where the temperatures are in degrees Celsius and "ln" refers to the natural logarithm. The constants are: a = 17.271 b = 237.7 °C This expression is based on the August–Roche–Magnus approximation for the saturation vapor pressure of water in air as a function of temperature.[3] It is considered valid for 0 °C < T < 60 °C 1% < RH < 100% 0 °C < Td < 50 °C Simple approximation There is also a very simple approximation that allows conversion between the dew point, the dry-bulb temperature and the relative humidity. This approach will be accurate to within about ±1 °C as long as the relative humidity is above 50%. The equation is: or This can be expressed as a simple rule of thumb: For every 1 °C difference in the dew point and dry bulb temperatures, the relative humidity decreases by 5%, starting with RH = 100% when the dew point equals the dry bulb temperature. where in this case RH is in percent, and T and Td are in degrees Celsius. The derivation of this approach, a discussion of its accuracy, comparisons to other approximations, and more information on the history and applications of the dew point are given in the Bulletin of the American Meteorological Society.[4]
  5. 5. Dew point 4 For temperatures in degrees Fahrenheit, or For example, a relative humidity of 100% means dew point is the same as air temp. For 90% RH, dew point is 3 degrees Fahrenheit lower than air temp. For every 10 percent lower, dew point drops 3 °F. Closer approximation A calculation used by NOAA is:[5] where: RH is relative humidity in percentage and is dew point in degrees Celsius and are the dry-bulb and wet-bulb temperatures respectively in degrees Celsius is the saturated water vapor pressure, in units of millibar, at the dry-bulb temperature is the saturated water vapor pressure, in units of millibar, at the wet-bulb temperature is the actual water vapor pressure, in units of millibar is "station pressure" (absolute barometric pressure at the site that humidity is being calculated for) in units of millibar (which is also hPa). For greater accuracy use the Arden Buck equation to find the water vapor pressures. Frost point The frost point is similar to the dew point, in that it is the temperature to which a given parcel of humid air must be cooled, at constant barometric pressure, for water vapor to be deposited on a surface as ice without going through the liquid phase. (Compare with sublimation.) The frost point for a given parcel of air is always higher than the dew point, as the stronger bonding between water molecules on the surface of ice requires higher temperature to break.[6] References [1] Horstmeyer, Steve (2006-08-15). "Relative Humidity....Relative to What? The Dew Point Temperature...a better approach" (http:/ / www. shorstmeyer. com/ wxfaqs/ humidity/ humidity. html). Steve Horstmeyer, Meteorologist, WKRC TV, Cincinnati, Ohio, USA. . Retrieved 2009-08-20. [2] http:/ / www. osha. gov/ pls/ oshaweb/ owadisp. show_document?p_table=INTERPRETATIONS& p_id=24602
  6. 6. Dew point 5 [3] "MET4 AND MET4A CALCULATION OF DEW POINT" (http:/ / www. paroscientific. com/ dewpoint. htm). Paroscientific, Inc. 4500 148th Ave. N.E. Redmond, WA 98052. 2007-09-13. . [4] M. G. Lawrence, "The relationship between relative humidity and the dew point temperature in moist air: A simple conversion and applications", Bull. Am. Meteorol. Soc., 86, 225–233, 2005 [5] http:/ / www. srh. noaa. gov/ images/ epz/ wxcalc/ rhTdFromWetBulb. pdf [6] Haby, Jeff. "Frost point and dew point" (http:/ / www. theweatherprediction. com/ habyhints/ 347/ ). . Retrieved September 30, 2011. External links • What is the dew point? ( • Dew point definition ( NOAA Glossary • Dew point formula ( • Often Needed Answers about Temp, Humidity & Dew Point ( temp-dewpoint/) from the sci.geo.meteorology • Humidity calculator ( • Dew point calculator in construction ( Humidity Humidity is a term for water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture, called the Absolute humidity.[1] In everyday usage, it commonly refers to relative humidity, expressed as a percent in weather forecasts and on household humidistats; it is so called because it measures the current absolute humidity relative to the maximum. Specific humidity is a ratio of the water vapor content of the mixture to the total air content (on a mass basis). The water vapor content of the mixture can be measured either as mass per volume or as a partial pressure, depending on the usage. Tropical forests and high-altitude regions often have high humidity. In meteorology, relative humidity indicates the likelihood of precipitation, dew, or fog. High relative humidity reduces the effectiveness of sweating in cooling the body by reducing the rate of evaporation of moisture from the skin. This effect is calculated in a heat index table, used during summer weather. Types Absolute humidity Absolute humidity is an amount of water vapor, usually discussed per unit volume. The mass of water vapor, , per unit volume of total moist air, , can be expressed as follows: Absolute humidity in air ranges from zero to roughly 30 grams per cubic meter when the air is saturated at 30 °C.[2] (See also Absolute Humidity table [3]) The absolute humidity changes as air pressure changes. This is very inconvenient for chemical engineering calculations, e.g. for clothes dryers, where temperature can vary considerably. As a result, absolute humidity is
  7. 7. Humidity 6 generally defined in chemical engineering as mass of water vapor per unit mass of dry air, also known as the mass mixing ratio (see below), which is much more rigorous for heat and mass balance calculations. Mass of water per unit volume as in the equation above would then be defined as volumetric humidity. Because of the potential confusion, British Standard BS 1339 (revised 2002) suggests avoiding the term "absolute humidity". Units should always be carefully checked. Most humidity charts are given in g/kg or kg/kg, but any mass units may be used. The field concerned with the study of physical and thermodynamic properties of gas-vapor mixtures is named Psychrometrics. Relative humidity Relative humidity is a term used to describe the amount of water vapor in a mixture of air and water vapor. It is defined as the ratio of the partial pressure of water vapor in the air-water mixture to the saturated vapor pressure of water at those conditions. The relative humidity of air depends not only on temperature but also on pressure of the system of interest. Relative humidity is normally expressed as a percentage and is calculated by using the following equation, it is defined as the ratio of the partial pressure of water vapor (H2O) in the mixture to the saturated vapor pressure of water at a prescribed temperature. [4] Relative humidity is an important metric used in weather forecasts and reports, as it is an indicator of the likelihood of precipitation, dew, or fog. In hot summer weather, a rise in relative humidity increases the apparent temperature to humans (and other animals) by hindering the evaporation of perspiration from the skin. For example, according to the Heat Index, a relative humidity of 75% at 80°F (27°C) would feel like 83.574°F ±1.3 °F (28.652°C ±0.7 °C) at ~44% relative humidity.[5] Specific humidity Specific humidity is the ratio of water vapor to dry air in a particular mass, and is sometimes referred to as humidity [6] ratio. Specific humidity ratio is expressed as a ratio of mass of water vapor, , per unit mass of dry air . That ratio is defined as: Specific humidity can be expressed in other ways including: or: Using the definition of specific humidity, the relative humidity can be expressed as However, specific humidity is also defined as the ratio of water vapor to the total mass of the system in meteorology.[7] "Mixing ratio" is used to name the definition in this section beginning.[8]
  8. 8. Humidity 7 Measurement There are various devices used to measure and regulate relative humidity. A device used to measure relative humidity is called a psychrometer or hygrometer. A humidistat is used to regulate the relative humidity of a building with a dehumidifier. These can be analogous to a thermometer and thermostat for temperature control. Humidity is also measured on a global scale using remotely placed satellites. These satellites are able to detect the concentration of water in the troposphere at altitudes between 4 and 12 kilometers. Satellites that can measure water vapor have sensors that are sensitive to infrared radiation. Water vapor specifically absorbs and re-radiates radiation in this spectral band. Satellite water vapor imagery plays an important role in monitoring climate conditions (like the formation of thunderstorms) and in the development of future weather forecasts. Climate While humidity itself is a climate variable, it also interacts strongly A hygrometer with other climate variables. The humidity is affected by winds and by rainfall. At the same time, 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 earths surface. This is the biggest non-radiative cooling effect at the surface. It compensates for roughly 70% of the average net radiative warming at the surface. Second, water vapor is the most important of all greenhouse gases. Water vapor, like a green lens that allows green light to pass through it but absorbs red light, is a "selective absorber". Along with other greenhouse gases, water vapor is transparent to most solar energy, as you can literally see. But it absorbs the infrared energy emitted (radiated) upward by the earths surface, which is the reason that humid areas experience very little nocturnal cooling but dry desert regions cool considerably at night. This selective absorption causes the greenhouse effect. It raises the surface temperature substantially above its theoretical radiative equilibrium temperature with the sun, and water vapor is the cause of more of this warming than any other greenhouse gas. The most humid cities on earth are generally located closer to the equator, near coastal regions. Cities in South and Southeast Asia are among the most humid, such as Kolkata, Chennai and Cochin in India, the cities of Manila in the Philippines and Bangkok in Thailand: these places experience extreme humidity during their rainy seasons combined with warmth giving the feel of a lukewarm sauna.[9] Darwin, Australia experiences an extremely humid wet season from December to April. Shanghai and Hong Kong in China also have an extreme humid period in their summer months. Kuala Lumpur and Singapore have very high humidity all year round because of their proximity to water bodies and the equator and overcast weather. Perfectly clear days are dependent largely upon the season in which one decides to travel. During the South-west and North-east Monsoon seasons (respectively, late May to September and November to March), expect heavy rains and a relatively high humidity post-rainfall. Outside the monsoon seasons, humidity is high (in comparison to countries North of the Equator), but completely sunny days abound. In cooler places such as Northern Tasmania, Australia, high humidity is experienced all year due to the ocean between mainland Australia and Tasmania. In the summer the hot dry air is absorbed by this ocean and the temperature rarely climbs above 35 degrees Celsius. In the United States the most humid cities, strictly in terms of relative humidity, are Forks and Olympia, Washington.[10] This fact may come as a surprise to many, as the climate in this region rarely exhibits the discomfort usually associated with high humidity. Dew points are typically much lower on the West Coast than on the East.
  9. 9. Humidity 8 Because high dew points play a more significant role than relative humidity in the discomfort created during humid days, the air in these western cities usually does not feel "humid". The highest dew points in the US are found in coastal Florida and Texas. When comparing Key West and Houston, two of the most humid cities from those states, coastal Florida seems to have the higher dew points on average. However, Houston lacks the coastal breeze present in Key West, and, as a much larger city, it suffers from the urban heat island effect.[11] A dew point of 86 degrees Fahrenheit was recorded in southern Minnesota on July 23, 2005, though dew points over 80 degrees Fahrenheit are rare there.[12] The US city with the lowest annual relative humidity is Las Vegas, Nevada, averaging 39% for a high and 21% as a low.[13] Air density and volume Relative humidity depends on water vaporization and condensation, which, in turn, mainly depends on temperature. Therefore, when applying more pressure to a gas saturated with water, all components will initially decrease in volume approximately according to the ideal gas law. However, some of the water will condense until returning to almost the same relative humidity as before, giving the resulting total volume deviating from what the ideal gas law predicted. Conversely, decreasing temperature would also make some water condense, again making the final volume deviating from predicted by the ideal gas law. Therefore, gas volume may alternatively be expressed as the dry volume, excluding the humidity content. This fraction more accurately follows the ideal gas law. On the contrary the saturated volume is the volume a gas mixture would have if humidity was added to it until saturation (or 100% relative humidity). Humid air is less dense than dry air because a molecule of water (M ≈ 18 u ) is less massive than either a molecule of nitrogen (M ≈ 28) or a molecule of oxygen (M ≈ 32). About 78% of the molecules in dry air are nitrogen (N2). Another 21% of the molecules in dry air are oxygen (O2). The final 1% of dry air is a mixture of other gases. For any gas, at a given temperature and pressure, the number of molecules present in a particular volume is constant – see ideal gas law. So when water molecules (vapor) are introduced into that volume of dry air, the number of air molecules in the volume must decrease by the same number, if the temperature and pressure remain constant. (The addition of water molecules, or any other molecules, to a gas, without removal of an equal number of other molecules, will necessarily require a change in temperature, pressure, or total volume; that is, a change in at least one of these three parameters. If temperature and pressure remain constant, the volume increases, and the dry air molecules that were displaced will initially move out into the additional volume, after which the mixture will eventually become uniform through diffusion.) Hence the mass per unit volume of the gas—its density—decreases. Isaac Newton discovered this phenomenon and wrote about it in his book Opticks.[14] Effects Animals and plants Humidity is one of the fundamental abiotic factors that defines any habitat, and is a determinant of which animals and plants can thrive in a given environment.[15] The human body dissipates heat by a perspiration and evaporation. Heat convection to the surrounding air, and thermal radiation are the primary modes of heat transport from the body. Under conditions of high relative humidity, the rate of evaporation of sweat from the skin decreases. Also, if the atmosphere is as warm as or warmer than the skin during times of high relative humidity, blood brought to the body surface cannot dissipate heat by conduction to the air, and a condition called hyperpyrexia results. With so much blood going to the external surface of the body, relatively less goes to the active muscles, the brain, and other internal organs. Physical strength declines, and fatigue occurs sooner than it would otherwise. Alertness and mental capacity also may be affected, resulting in heat stroke or hyperthermia.
  10. 10. Humidity 9 Human comfort Humans are sensitive to humid air because the human body uses evaporative cooling as the primary mechanism to regulate temperature. Under humid conditions, the rate at which perspiration evaporates on the skin is lower than it would be under arid conditions. Because humans perceive the rate of heat transfer from the body rather than temperature itself, we feel warmer when the relative humidity is high than when it is low. Some people experience difficulty breathing in high humidity environments. Some cases may possibly be related to respiratory conditions such as asthma, while others may be the product of anxiety. Sufferers will often hyperventilate in response, causing sensations of numbness, faintness, and loss of concentration, among others.[16] Air conditioning reduces discomfort in the summer not only by reducing temperature, but also by reducing relative humidity. In winter, heating cold outdoor air can decrease relative humidity levels indoor to below 30%, leading to discomfort such as dry skin and excessive thirst. Electronics Many electronic devices have humidity specifications, for example, 5% to 95%. At the top end of the range, moisture may increase the conductivity of permeable insulators leading to malfunction. Too low relative humidity may make materials brittle. A particular danger to electronic items, regardless of the stated operating humidity range, is condensation. When an electronic item is moved from a cold place (e.g., garage, car, shed, an air conditioned space in the tropics) to a warm humid place (house, outside tropics), condensation may coat circuit boards and other insulators, leading to short circuit inside the equipment. Such short circuits may cause substantial permanent damage if the equipment is powered on before the condensation has evaporated. A similar condensation effect can often be observed when a person wearing glasses comes in from the cold. It is advisable to allow electronic equipment to acclimatise for several hours, after being brought in from the cold, before powering on. Some electronic devices can detect such a change and indicate, when plugged in and usually with a small droplet symbol, that they cannot be used until the risk from condensation has passed. In situations where time is critical, increasing air flow through the devices internals when, such as removing the side panel from a PC case and directing a fan to blow into the case will reduce significantly the time needed to acclimatise to the new environment. On the opposite, very low relative humidity level favors the buildup of static electricity, which may result in spontaneous shutdown of computers when discharges occur. Apart from spurious erratic function, electrostatic discharges can cause dielectric breakdown in solid state devices, resulting in irreversible damage. Data centers often monitor relative humidity levels for these reasons. Building construction Traditional building designs typically had weak insulation, and it allowed air moisture to flow freely between the interior and exterior. The energy-efficient, heavily-sealed architecture introduced in the 20th century also sealed off the movement of moisture, and this has resulted in a secondary problem of condensation forming in and around walls, which encourages the development of mold and mildew. Additionally, buildings with foundations not properly sealed will allow water to flow through the walls due to capillary action of pores found in masonry products. Solutions for energy-efficient buildings that avoid condensation are a current topic of architecture.
  11. 11. Humidity 10 References [1] Wyer, S.S., "A treatise on producer-gas and gas-producers", (1906) The Engineering and Mining Journal, London, p.23 [2] http:/ / www. britannica. com/ eb/ article-53259/ climate#292984. hook [3] http:/ / www. tis-gdv. de/ tis_e/ misc/ klima. htm [4] Perry, R.H. and Green, D.W, Perrys Chemical Engineers Handbook (7th Edition), McGraw-Hill, ISBN 0-07-049841-5 , Eqn 12-7 [5] http:/ / en. wikipedia. org/ wiki/ Heat_index#Formula [6] Cengel, Yunus and Boles, Michael, Thermodynamics: An Engineering Approach, 1998, 3rd edition, McGraw-Hill, pp. 725–726 [7] AMS Glossary: specific humidity (http:/ / amsglossary. allenpress. com/ glossary/ search?id=specific-humidity1) [8] http:/ / amsglossary. allenpress. com/ glossary/ search?id=mixing-ratio1 [9] BBC – Weather Centre – World Weather – Average Conditions – Bangkok (http:/ / www. bbc. co. uk/ weather/ world/ city_guides/ results. shtml?tt=TT002890) [10] What Is The Most Humid City In The U.S.? | KOMO-TV – Seattle, Washington | News Archive (http:/ / www. komotv. com/ news/ archive/ 4092941. html) [11] Answers: Is Florida or Texas more humid: September 3,2003 (http:/ / www. usatoday. com/ weather/ resources/ askjack/ 2003-09-03-answers-fla-texas-humidity_x. htm) [12] High Dew Point Temperatures: July 23, 2005 (http:/ / climate. umn. edu/ doc/ journal/ dewpoint050723. htm) [13] http:/ / www. cityrating. com/ relativehumidity. asp [14] Isaac Newton (1704). Opticks (http:/ / books. google. com/ books?id=iTpXLrPR2TQC& printsec=frontcover& dq=isaac+ newton+ optics). Dover. ISBN 978-0-486-60205-9. . [15] C.Michael Hogan. 2010. Abiotic factor. Encyclopedia of Earth. eds Emily Monosson and C. Cleveland. National Council for Science and the Environment (http:/ / www. eoearth. org/ article/ Abiotic_factor?topic=49461). Washington DC [16] "I have trouble breathing in high relative humidity - Lung & Respiratory Disorders / COPD Message Board - HealthBoards" (http:/ / www. healthboards. com/ boards/ showthread. php?t=409092). . Retrieved 18 July 2011. • United States Environmental Protection Agency, "IAQ in Large Buildings" ( largebldgs/i-beam_html/ch2-hvac.htm#F2.6). Retrieved Jan. 9, 2006. External links • Glossary definition of absolute humidity ( shtml#absolute_humidity) – National Science Digital Library • Glossary definition of psychrometric tables ( – National Snow and Ice Data Center • Glossary definition of specific humidity ( – National Snow and Ice Data Center • FREE Humidity & Dewpoint Calculator ( instruments/rhcalc) – Vaisala • Free Windows Program, Dewpoint Units Conversion Calculator ( – PhyMetrix • Free Online Humidity Calculator ( humidity_measurement-feuchtemessung-mesure_de_l_humidite/humidity-calculator-feuchterechner-mr) – Calculate about 16 parameters online with the Rotronic Humidity Calculator
  12. 12. Article Sources and Contributors 11 Article Sources and Contributors Dew point  Source:  Contributors: Ac44ck, Adam Bishop, Agentilini, Alansohn, Aldaron, Alex Bakharev, Anclation, Andkaha, Andre Engels, Andrea105, Andris, Arjayay, Arnach, Atlant, Aushulz, Babangida Ingawa, Belg4mit, Bettymnz4, BirdValiant, Bonkerzbanks, Bradeos Graphon, Brendenhull, Bryan Derksen, Btm1, Bubba73, Bumm13, Buster2058, CWii, CalgaryWikifan, Carlroller, Chernysh, Christophenstein, CountMacula, Crimson123, Cyclist, Dbrunner, Deewhite, DelmhorstWiki, DerHexer, Deusnoctum, Djd sd, Dmd, Doctorevil64, Donarreiskoffer, Donwarnersaklad, Download, Drdewlittle, Easchiff, Eclectica, Editor182, Eeekster, Ellywa, Emerson7, Epbr123, Esperant, Ewlyahoocom, F-402, F117-A, FiggyBee, Filu, Fr.bernat, Frodet, Frogsaregreen, Funandtrvl, Gaius Cornelius, Gary King, Gene Nygaard, Giftlite, Glenn, Glrx, GregBenson, Groogle, Guaka, Gurch, Haham hanuka, Halcionne, Hard Raspy Sci, Harriv, Harry, Heds, Hephaestos, Hohum, Hygrotrace, Ignasv, Iranianson, Irish Pearl, Iulian.serbanoiu, Iwehrman, Ixfd64, J.delanoy, JFreeman, JaGa, Jauerback, Jay Litman, Jayarcee, Jfcarr, JidGom, Jim.henderson, Jmcc150, Jpiterow, Jrh98409, Jusdafax, Kate, Keilana, Kelisi, Klaus, Kvuo, Landrumkelly, Lawlaw831, Leszek Jańczuk, LilHelpa, Lmviterbo, Logan, Loren.wilton, Lupo, MGTom, Manco Capac, Marshman, Mathew Roberson, Mav, Mbeychok, MeekSaffron, Megaman en m, Mgiganteus1, Michael Hardy, Mlpearc, Mu301, NathanHurst, Ncmvocalist, Nick Dillinger, NicoFrankhuizen, NotWith, Oberono, Onlyemarie, Oroso, Ouishoebean, OwenBlacker, Palica, Pdcook, Penglish, Pflatau, Pharazs, Phatmattbaker, PhilKnight, PigFlu Oink, Pinethicket, Pocketengineer, PrometheusX303, Pyrotec, QueenCake, RadarCzar, Radiojon, RattleMan, Razorflame, ReaverFlash, Reedy, Retiono Virginian, Rifleman 82, Robyvecchio, Romanskolduns, Ron E, Ronhjones, Rracecarr, RxS, Rxjensen, Ryankrameretc, Sam Korn, Samuel, Sardanaphalus, Scarian, Scooter, Sergivs-en, Sharcho, Shawnc, Sjö, Skew-t, Skrelk, Soap, Sophie1979, SpectrumAnalyser, Spiff666, StaticGull, StaticSan, Steve2011, Strait, Stratadrake, StuartH, THEN WHO WAS PHONE?, Taquito1, Tartarugayankee, The Thing That Should Not Be, TheGrimReaper NS, Thegreatdr, Thewopr, Tide rolls, Time9, Tobyc75, Tom, Tqwhite, Tunabex, Typinaway, Ukexpat, Ulfpip, Unusual Cheese, Urhixidur, Vox Rationis, Vsmith, Welsh, Wiki alf, William M. Connolley, Wizzard2k, Woohookitty, Wyatts, X arch, Zapvet, Zidonuke, ZildjianAVC, Zocky, Zomno, 493 anonymous edits Humidity  Source:  Contributors: 16@r, 1exec1, 5 albert square, A3RO, ACrush, ADNghiem501, Abdull, Abrech, Abu-Fool Danyal ibn Amir al-Makhiri, Achituv, Adamd1008, AdjustShift, Aeonx, Ahoerstemeier, Ainlina, Airplaneman, Ajraddatz, AlanD, Alansohn, Alphachimp, Anclation, Andyvine, Anomie, Anonywiki, Anwar saadat, Arjun01, Artmario2001, Ashvidia, Auntof6, AxelBoldt, BMXrider1296, Beland, Berberisb, Bergsten, Bignoter, Boardered, Bob Pragnell, Bobb4321, Bobo192, Bodnotbod, Boothy443, Br77rino, Brastein, Brockert, Brownout, Buck Mulligan, Burner0718, Burst tools 353, Buster2058, Byrial, CALR, CTZMSC3, CWii, Cacycle, Caliprincess, Calltech, Caltas, Calvin 1998, CambridgeBayWeather, Cant sleep, clown will eat me, CanisRufus, Capricorn42, CardinalDan, Carultch, Catrucat, Cffrost, Cflm001, Citikiwi, Cookie90, Copangry^^, Correogsk, Crookloren, Curb Chain, D-dawg, DA3N, Daniel0ng, DanielCD, Dantadd, Davehi1, Davewild, Dawnseeker2000, Dhollm, Dikke poes, Direnzoa, Discospinster, Djd sd, Dmitri Yuriev, Drdewlittle, Dreadstar, Dusty777, Ebraminio, Eman2129, Emperorbma, Emwave, Enviroboy, EoGuy, Epbr123, Erik9, Ewlyahoocom, Eyeresist, Fgnievinski, Finngall, Flowerparty, Flubeca, Fortdj33, Frap, Fredrostein, Fykewiki, GBeeley, GFrege, Gareth McCaughan, Gareth274, Garfield226, Gaviidae, Genrallex, Giftlite, Gimboid13, Gmaxwell, Goatman57, Goodvac, Graham87, GregBenson, Grievous Angel, GrouchyDan, Gurch, Gzur, Gökhan, Haham hanuka, Hairy Dude, Hallows AG, Hard Raspy Sci, Hawaii2001, Hennessey, Patrick, Hermit thrush, Heron, Hmains, Hobart, Hongkonger, Hramat, Hua001, Humitrap, Hyperman 42, II MusLiM HyBRiD II, IQuestie, Icairns, Immunize, Intellicast, Iridescent, Istcol, Ivan Štambuk, IvanLanin, Ixfd64, J.delanoy, JJ cool D, JNW, Jacqui M, Jagged 85, Jakes18, Jatosado, Jbergerot, Jcdietz03, Jeff Silvers, Jerome Charles Potts, Jerry, Jfdwolff, Jj137, Joao Xavier, JohnOwens, Jthorsen3315, Juan jesus rodriguez alvarez, Kapow, Katalaveno, Ken Gallager, King of Hearts, KonaScout, Koodoo, KrakatoaKatie, Kurowoofwoof111, Kurt Shaped Box, L Kensington, L0ngpar1sh, LOL, Lachaume, LarryGilbert, Leon7, Lights, Loren.wilton, Lradrama, Lt. penguin, Ma11achy, Majorclanger, Majorly, Maksud, Maky, Marc Kupper, Margin1522, Martial75, Martin-Alfred, Mausy5043, Maxis ftw, Meneitherfabio, Missotos, Mnbitar, Momo Momone, Mormegil, Mr0t1633, Mschel, Musicmaster890, N4nojohn, NERIC-Security, NERIUM, NPrice, Nakon, Names are hard to think of, Natalie Erin, NellieBly, NetherlandishYankee, Newtontwo, Nick R Hill, NicoFrankhuizen, Nikki, Nilfanion, Nis81, Nixón, Nn123645, Noca2plus, Nono64, NormalAsylum, NorwegianBlue, Notedgrant, Nplummer, Nruibal, Nurg, Ofekalef, Ojcookies, Ojigiri, Ozag99, Paul August, Persian Poet Gal, Pevarnj, Pflatau, Phatmattbaker, Philip Trueman, Phrost6, Pierre cb, PierreAbbat, PigFlu Oink, Pinethicket, Pol430, Posmentier, Ps3person, Q;wleitpiouasdo;, Qmwne235, Quasipalm, QuiteUnusual, RainbowOfLight, Ravanacker, Raven4x4x, Rdsmith4, Reaper Eternal, Reinthal, Rkinch, Rkmlai, RogerVan, Romanm, Ron E, Runningonbrains, SFN4, SailorfromNH, SaintNULL, Sam.Holloway, Samw, Samwb123, Sardanaphalus, SchfiftyThree, Seaphoto, Sgeureka, Shinjiman, Shizhao, Shoefly, Skidmark, Skizzik, Slippyd, Slon02, SmilesALot, Smyth, South Bay, Species8473, StealthFox, Stemonitis, Stephan Leeds, Steven Zhang, StuRat, Surv1v4l1st, THEN WHO WAS PHONE?, Tdscully, Teetaweepo, Telecineguy, Tgeairn, The Thing That Should Not Be, The ed17, TheHYPO, Thingg, Tiddly Tom, Tide rolls, Tommy2010, Transisto, Truethug, Ummit, Useight, Veinor, Versus22, Vipinhari, Vsmith, Vssun, W.F.Galway, Wakebrdkid, Wavelength, Wayne Slam, Wdacooper, Wdflake, Whoareyou234234, Wikem, Wilthain, Wimt, Wmahan, Xdenizen, Xliuwlksollzll, YK Times, Yurivict, Zepheus, Zephyris, Zhuozhi521, ‫ 927 ,ﻓﺮﻫﺎﺩﻓﺮ‬anonymous edits
  13. 13. Image Sources, Licenses and Contributors 12 Image Sources, Licenses and Contributors Image:dewpoint.jpg  Source:  License: Creative Commons Attribution-ShareAlike 3.0 Unported  Contributors: Original uploader was GregBenson at en.wikipedia Image:Dewpoint-RH.svg  Source:  License: Creative Commons Attribution-Share Alike  Contributors: Easchiff File:Cloud forest mount kinabalu.jpg  Source:  License: Creative Commons Attribution-Sharealike 2.5  Contributors: Davepape, Gilgameshkun, MPF, NepGrower, Twinsday, 4 anonymous edits Image:Umidaderelativa.jpg  Source:  License: Agência Brasil  Contributors: José Cruz/ABr
  14. 14. License 13 License Creative Commons Attribution-Share Alike 3.0 Unported //