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What is dew point in simple words?

What is the Dew Point? – What is the dew point and how does it affect how comfortable you feel? The definition of dew point is the temperature point at which the air can hold no more water (water vapor) and is one of the factors in the heat index. It is always lower or the same as the air temperature.

What does dew point tell you?

Dew point vs. humidity – The dew point is the temperature to which the air must be cooled in order for it to become saturated, It provides a measure of the actual amount of water vapor in the air – so the higher the dew point, the more moisture in the air.

1. Relative humidity increases as the air temperature drops to the dew point or the dew point rises to the air temperature (since the humidity is relative to the air temperature).
2. Once the air temperature and dew point meet, the air becomes saturated and the relative humidity reaches 100%.
3. The dew point can never be higher than the air temperature.

Similarly, as the air temperature rises and/or the dew point drops, the relative humidity decreases because the air is getting farther away from saturation. This chart illustrates the key differences between relative humidity and dew point. (FOX Weather) Using the 100% relative humidity example at an air temperature of 20 degrees, that would mean the dew point is also 20 degrees. That’s indicative of a bone-dry air mass even though the relative humidity says otherwise.

In general, once the dew point exceeds 60 degrees, there’s a lot of water vapor in the air, which is what gives the air that muggy feel. At 60% relative humidity with a temperature of 80 degrees and a dew point of 65 degrees, you’re probably going to break a sweat while doing anything strenuous – even at night or on a cloudy day – because dew points in the mid-60s are indicative of a muggy air mass.

WHAT IS THE HEAT INDEX AND WHY IS IT IMPORTANT TO YOUR HEALTH? This is why relative humidity is practically useless when trying to determine how humid the air is outside. You’re probably not going to break a sweat at 20 degrees, even with 100% relative humidity.

What does 70 dew point mean?

There is a difference between dew point and relative humidity Relative humidity is temperature dependent while dew point is not Dew point measures how much moisture is in the air Dew point will be a more reliable in determing comfort level during warm summer days

– Take the example where the dew point is 65 degrees and the air temp is 65 degrees. Relative humidity in this situation is 100%. Hold that dew point at 65 with the air temp rising to 95. Relative humidity drops to about 37%. In this scenario, it would feel quite humid or muggy and even uncomfortable despite the relative humidity being fairly low.

1. In fact, the heat index temperature – what it actually feels like outside – would be 98 degrees! We can see from these examples that the closer the temp is to the dew point, the higher the relative humidity.
2. The farther apart they are the lower the relative humidity.
3. Let’s now look at dew point temperature: The general rule of thumb is that dew points in the 50s or lower is comfortable during the warm months.60 to 65 and it feels sticky or humid.

Dews above 65 are downright muggy and even tropical when they reach the 70s. Now, a dew point in the 50s at night with temps in the 50s will feel damp with high relative humidity in this scenario. You tend to get at least patchy fog and dewy grass galore.

1. We’ve also had days where the dew point is around 70 along with a similar air temp and it’s been raining.
2. In this scenario relative humidity is high and it would tend to feel damp and clammy, but not so much muggy or tropical.
3. Both measurements are useful, but as a general guide on and warm or hot day it’s the dew point temp that will be a more reliable guide for determining comfort level.

: How to tell if it will feel humid or muggy on a warm day

Does Dewpoint make it feel hotter?

How does dew point affect the temperature you feel? – In warm, sultry weather, moisture in the air can impede your body’s ability to cool down. One of the ways your body cools itself is by the evaporation of moisture from your skin. When the air is moist, this process slows down—and you feel hotter for longer. If you’re used to the tropics, you may find the ranges in this scale low—particularly during spring and summer where dew points are commonly above 24 °C. On the other hand, if you’re from southern Australia, you might find these ranges high. So that old adage might better run, ‘It’s not the heat, it’s the moisture in the air, which at higher temperatures is more reliably indicated by dew point than humidity’.

Is dew point more important than humidity?

Dew Point Definition: – The temperature where any air mass when cooled to that temperature reaches 100% humidity. It is expressed as measure of degrees. Dew point is a better measure of absolute measure of the water vapor in the air within a given air mass.

What is the highest dew point ever recorded?

The highest dew point ever recorded, 95°F (35°C), was recorded at Dhahran, Saudi Arabia, on July 8, 2003. With an air temperature of 108°F (42°C), the heat index was 178°F (81°C).

What happens when dew point is 100?

When relative humidity is at 100%, (such as when dew point temperature and actual air temperature are the same), this means there is a maximum amount of moisture present in the air at that particular temperature. As a result, this saturation could lead to fog, dew, clouds and, in other cases, precipitation.

Is 70 percent humidity high?

What is humidity? – Humidity is simply the concentration of water vapor present in the air, while relative humidity measures the amount of water in the wait in relation to the maximum amount of water vapor it can hold. For example, when outdoor humidity reaches 100%, the air cannot hold any more moisture and it starts to rain. Research from the Building Science Corporation found that humidity of 70% or higher adjacent to a surface can cause serious damage to the property. The Health and Safety Executive recommends that relative humidity indoors should be maintained at 40-70%, while other experts recommend that the range should be 30-60%.

What is dew point when raining?

The dew point is the temperature at which the air can exactly hold the amount of moisture present. When raining, at any given temperature, the atmosphere can hold so much water vapour. So the dew point is equal to the room temperature.

Is 100% dew point rain?

Must it be raining when the humidity reaches 100%? A relative humidty measurement of 100% does not necessarily mean that rain is falling. It just means that the air is holding as much moisture as it can at a given temperature, in the form of water vapor, which is an invisible gas.

• However, near 100% relative humidity, you can get water vapor condensing into very small water droplets to form clouds, including fog near the surface.
• Also, the relative humidity at the ground does not have to be 100% to get rainfall.
• It often happens in the western United States, for instance, that you will have clouds producing rainfall or snowfall which then falls through very dry (low relative humidity) air near the surface and evaporates before it even hits the ground.

This is called virga. – Michael Bell : Must it be raining when the humidity reaches 100%?

Is humidity 100% at dew point?

Dew Point vs Humidity Dew Point vs. Humidity The dew point is the temperature the air needs to be cooled to (at constant pressure) in order to achieve a relative humidity (RH) of 100%. At this point the air cannot hold more water in the gas form. If the air were to be cooled even more, water vapor would have to come out of the atmosphere in the liquid form, usually as fog or precipitation.

The higher the dew point rises, the greater the amount of moisture in the air. This directly affects how “comfortable” it will feel outside. Many times, relative humidity can be misleading. For example, a temperature of 30 and a dew point of 30 will give you a relative humidity of 100%, but a temperature of 80 and a dew point of 60 produces a relative humidity of 50%.

It would feel much more “humid” on the 80 degree day with 50% relative humidity than on the 30 degree day with a 100% relative humidity. This is because of the higher dew point. So if you want a real judge of just how “dry” or “humid” it will feel outside, look at the dew point instead of the RH.

less than or equal to 55: dry and comfortable between 55 and 65: becoming “sticky” with muggy evenings greater than or equal to 65: lots of moisture in the air, becoming oppressive

: Dew Point vs Humidity

What happens if dew point is higher than temperature?

Thus when the dew point temperature and the air temperature are the same, the air is said to be saturated- the air cannot hold any more water. So to summarize, if the dewpoint is the same or higher than the current temperature, then dew (or fog) will occur.

Does a low dew point make it colder?

Let’s Get to the Point – Now that we’ve had a quick humidity recap, it’s time to explain how moisture can impact overnight temperatures. The low temperature will rarely fall below that night’s dew point temperature. The only exception is if another air mass is moving in, forcing moisture out.

1. Once the temperature drops to the dew point, latent heat is released and condensation begins.
2. Condensation is a warming process, so the addition of heat offsets some or all of the further cooling.
3. This is especially true for dew points above 55 degrees.
4. If the dew point is much lower than the temperature in the evening, the air will cool off faster than if the dew point is closer to the temperature.

This is why dry regions such as the High Plains and deserts have such large differences between the high and low temperature. Moisture-rich areas, such as along the coast, tend to have a smaller spread between the high and low temperature. In conclusion, lower humidity means temperatures will quickly drop overnight.

What does 100 humidity feel like?

When the humidity is at 100%, it means the air is holding the maximum amount of moisture it can at a given temperature. This condition is often described as ‘ feeling sticky’ or ‘feeling muggy.’ Here’s what it can feel like: Sensation of Moisture: The air feels damp and saturated with moisture.

Can temperature ever be lower than dew point?

Meteorologists refer to the temperature at which this takes place as the dew point. The air must be this temperature for condensation to occur. Although the air temperature can never go lower than the dew point, the dew point can drop as the temperature goes down.

What will likely happen if there is 100% humidity?

RELATIONSHIP OF DEWPOINT AND RELATIVE HUMIDITY TO CLOUDS AND PRECIPITATION: – If the relative humidity is 100 percent (i.e., dewpoint temperature and actual air temperature are the same), this does NOT necessarily mean that precipitation will occur. 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). However, for precipitation to occur, the air must be rising at a sufficient rate to enhance condensation of water vapor into liquid water droplets or ice crystals (depending on air temperature) and to promote growth of water droplets, supercooled droplets, and/or ice crystals in clouds.

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.

“Cloud microphysics” is the study of droplet and ice crystal production and growth within clouds and their relationship to precipitation.

Does higher dew point mean more rain?

Observed Dew Point Temperature: indicates the amount of moisture in the air

Observed Dew Point Temperature indicates the amount of moisture in the air The value highlighted in yellow located in the lower left corner (in the diagram above) is the dew point temperature in degrees Fahrenheit. In this example, the reported dew point temperature is 58 degrees. Dew points indicate the amount moisture in the air. The higher the dew points, the higher the moisture content of the air at a given temperature. Dew point temperature is defined as the temperature to which the air would have to cool (at constant pressure and constant water vapor content) in order to reach saturation.

A state of saturation exists when the air is holding the maximum amount of water vapor possible at the existing temperature and, When the dew point temperature and air temperature are equal, the air is said to be saturated. Dew point temperature is NEVER GREATER than the air temperature. Therefore, if the air cools, moisture must be removed from the air and this is accomplished through condensation,

This process results in the formation of tiny water droplets that can lead to the development of fog, frost, clouds, or even precipitation. can be inferred from dew point values. When air temperature and dew point temperatures are very close, the air has a high relative humidity.

The opposite is true when there is a large difference between air and dew point temperatures, which indicates air with lower relaitve humidity. Locations with high relative humidities indicate that the air is nearly saturated with moisture; clouds and precipitation are therefore quite possible. Weather conditions at locations with high dew point temperatures (65 or greater) are likely to be uncomfortably humid.

: Observed Dew Point Temperature: indicates the amount of moisture in the air

What is the dew point of 90% humidity?

Simple approximation – There is also a very simple approximation that allows conversion between the dew point, temperature, and relative humidity. This approach is accurate to within about ±1 °C as long as the relative humidity is above 50%: 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. 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, can be found in an article published in the Bulletin of the American Meteorological Society, For example, a relative humidity of 100% means dew point is the same as air temp. For 90% RH, dew point is 3 °F lower than air temperature. For every 10 percent lower, dew point drops 3 °F.

Which country has the highest dew point?

The world’s highest reported dew point is 95 degrees, recorded on July 8, 2003, at Dhahran, Saudi Arabia, located on the Persian Gulf. With a 95-degree dew point, the lowest possible heat index there (temperature also at 95 degrees) would be 161.

What countries have the highest dew point?

1) Most Humid City in the World – Pearl-Qatar – an artificial island in Qatar There are several contenders for the most humid city in the world, based on which city across the globe has the highest dewpoint, and records incredibly high dewpoints all year round. Cities located almost directly on the Equator, have a constant wet season and intense heat, and are close to a large stretch of warm water are most likely contenders.

• Kuala Lumpur
• Singapore
• Jakarta
• Manaus

However, other cities have recorded higher dew points, particularly around the Gulf of Aden and Persian Gulf regions, but only during the summer months. Kuala Lumpur and Singapore record incredibly high dewpoints across the entire year. Average maximum dew points in Kuala Lumpur reach an impressive high of 83.3 °F ( 28.5°C) during April, only falling to 80.2°F ( 26.8°C) during August. However, Singapore is slightly more humid, with maximum average dewpoints of 83.8 ° F ( 28.8°C) recorded in April, and 81.9°F ( 27.7°C) recorded in August.

• This is not surprising as Kuala Lumpur and Singapore are located around 340 km (210 miles) and 140 km (90 miles) north of the Equator respectively, with an overhead Sun providing intense heat all year round.
• Both cities are also located close to a large body of water – Singapore borders the large Singapore Strait, whereas the centre of Kuala Lumpur is located around 40 km (25 miles) to the west of the Melacca Strait.

The strong sunlight evaporates water from the warm surrounding seas, which in turn increases the moisture content of the air. However, Manaus in Brazil also records comparatively high dewpoint values throughout the year. With a latitude of 3°S, and its location on the Amazon River in the middle of the Amazon Rainforest, it is no surprise that the average maximum dewpoint fluctuates between 81.3 ° F (27.4°C) in July and 83.7°F ( 28.7°C) in October.

Some cities around the world have seen higher dew point values than those already presented, but only during certain times of the year. Bangkok sees higher average maxima – of 85.3°F ( 29.6°C) in April and 83.7°F ( 28.7°C) in September, but dewpoints fall to below 78.8 ° F ( 26°C) during December and January.

Other high values are recorded seasonally, particularly around the Red Sea, Gulf of Aden and Persian Gulf regions. Despite being on the edge of a hyper-arid desert region, large evaporation rates and high sea surface temperatures combine to produce incredibly high humidity along the coastal regions between May and October. Jakarta, the capital of the Republic of Indonesia The highest dewpoint recorded on Earth is in the city of Dhahran in Saudi Arabia, which experienced a dewpoint of 95°F (35°C) in 2003 – however, dewpoints above 90 ° F ( 32°C) are rare, and only occur in these regions during the summer months. (Hosseinzadeh Talaee et al.) Identifying the most humid country in the world depends on numerous factors. Many countries have large differences in terrain, elevation, and climate. Although the highest dewpoints in the world have been recorded on land bordering the Persian Gulf, Gulf of Aden, and the Red Sea, these are only limited to the coastal regions of the countries which border those seas.

For example, Saudi Arabia, Oman, and Yemen record dewpoints in excess of 86°F ( 30°C) along their coastal regions, but their large desert interiors located far from the surrounding seas record comparatively low dewpoint values.

This piece examines countries that have rather high dewpoints recorded across most of their terrain, and maintain the values during much (if not all) of the year. The small country of Qatar is a strong contender for being the most humid country in the world.

• Despite its desert landscape and hyper-arid climate, it is a narrow peninsula located on the western side of the Persian Gulf, meaning that it is surrounded by water on its eastern, northern and western sides.
• Its maximum width of 90 km (55 miles) across means that much of the country is close to water.

Its capital city, Doha, records dewpoints exceeding 81 ° F ( 27°C) between July and October peaking at 86 ° F ( 30°C) in September. However, there is a wide seasonal difference, with dewpoint values below 68 ° F ( 20°C) between December and March, meaning that the incredibly humid summer months are cancelled out by the winter months, which are significantly less humid.

• Other contenders are likely to be an island, archipelago or coast-bordering nation that is close to the Equator, and has much of its terrain at or near sea level.
• Although many Equatorial countries that include large rainforests are rather humid, these often include many large upland areas that are cooler due to the lapse rate, making these countries less humid overall than other nations.

Singapore is both a city and a small country in its own right – since its average maximum dewpoint fluctuates between 81 – 84°F (27.7 – 28.895°C) throughout the year, it would be fair to declare this as the world’s most humid country overall. But what about countries with a larger land mass? Both Malaysia and Indonesia have large lowland areas, despite the presence of large mountain ranges.

• Indonesia in particular straddles both sides of the Equator, and is made up of a vast archipelago that includes many islands surrounded by warm seas that often top 86 ° F ( 30°C).
• Inland areas of Indonesia also record high humidity levels, such as the city of Palembang around 75 km (45 miles) from the nearest sea.

Here, dewpoint levels between 82 – 84 ° F ( 28°C and 29°C) are recorded throughout the year – this incredible humidity is felt across much of Indonesia all year round.

Which area of the country has the highest dew point?

Record Dew Point Temperatures Just recently the Minnesota State Climate Office issued a statement declaring the 88° dew point temperature measured at Moorhead (on the Red River across from Fargo, North Dakota) between 7pm and 9pm on July 19, 2011 as a new all-time state record for the highest such reading ever observed.

• This would also be one of the highest dew points ever observed in the United States.
• Here is a brief summary of record dew point levels from both the U.S.A.
• And around the world.
• The 88° Dew Point Measured at Moorhead, Minnesota on July 19, 2011 One might assume that the highest dew points measured in the United States would be those observed during in areas along or near the coast of the Gulf of Mexico during the summer months.

Although for the most part this is true the other region that occasionally seems to record extraordinary heat and humidity is the Upper Midwest. I have not been able to discover just why the dew points in Iowa, Minnesota, and Wisconsin sometimes are higher than anywhere else in the United States during exceptional heat waves versus, say, Missouri or other states that are generally more humid and also endure exceptional summer heat. Two graphics illustrating the affect of humidity on the apparent feel of the temperature: at top is NOAA’s Heat Index chart (% of humidity with air temperature) and below that the effect of dew point with air temperature. Unfortunately the dew point table does not consider dew points above 82°.

• On July 19th not only did Moorhead record its highest dew point on record but so did Minneapolis with an 82° (and possibly even 84° for a five minute period between 3:21-3:27 pm) on the same day.
• Another site in Minnesota, Madison, also registered an 88° dew point (although this site may not be considered an official reporting station).

The NWS office in Grand Forks, North Dakota issued this statement explaining how heavy rainfall the morning of the event had saturated the soil and left ponding water near the instrument site. Furthermore, the AWOS is surrounded by sugar beets and soy beans “two of the most prodigious transpiring plants”. A photograph of the Moorhead Airport Automated Station tat registered the 88° dew point on July 19th. Photo courtesy of the Grand Forks, North Dakota National Weather Service Office. Highest Dew Point Measurements in the United States Last summer (2010), Newton, Iowa recorded an 88° dew point on July 14th.

• Chicago, Illinois’s highest dew point was 83° at 8 a.m.
• On July 30, 1999 as was Milwaukee, Wisconsin’s with an 82° the same day.
• But it was during the July heat wave of 1995 that the highest dew point of all was measured in the Upper Midwest: 90° at Appleton, Wisconsin at 5 p.m.
• On July 13th of that summer.

The air temperature stood at 101° in Appleton at that time leading to a heat index reading of 148°, perhaps the highest such reading ever measured in the United States. Here are the METARS for Appleton that day: METARS chart for Appleton, Wisconsin on July 13, 1995 from wunderground.com. The July 1995 heat wave resulted in the deaths of 750 people in Chicago and other cities in the region recorded amazing dew points as well such as Cedar Rapids, Iowa: 84° (heat index 129°) and Oelwein, Iowa 85° (heat index 131°).

• Unusually high dew points in the region persisted for a couple days, aided by evaporation from soil and a stable layer of air aloft that prevented moist air in the lowest few thousand feet from mixing with drier air above.
• This was also the case in Minnesota and North Dakota last month on July 19th.
• Aside from Appleton, the only other instances of 90° or higher dew points I am aware of are the following: 91° at Melbourne, Florida at 2 p.m.

on July 12, 1987 (air temperature 95°) and 90° at New Orleans Naval Air Station at 5 p.m. on July 30, 1987 (air temperature 91°). Both of these records have not been vetted for accuracy. Record high dew points seem to be a particularly difficult record to verify.

1. On the East Coast I can find no reference to what New York City’s highest dew point might have been.
2. Philadelphia’s highest such was 82° on July 15, 1995 (the heat index peaked at 129°).
3. Syracuse, New York’s record was 77° on July 4, 1999.
4. Anecdotal on-line reports claim an 86° dew point at Virginia Beach, Virginia sometime during the summer of 1998.

In general, it may be assumed that the highest dew points on record for most places east of the Great Plains would be in the 77°-85° range. Highest Dew Point Levels in The World The hottest most humid regions of the world are the coastal areas of The Persian Gulf, Red Sea, and Gulf of Aden. Map of the Arabian Peninsula region, the coastal areas of which record the highest dew points in the world. Boosaso (referenced below) is located on the Gulf of Aden coast of Somalia just visible at the bottom portion of the map. Dhahran, Saudi Arabia is located on the Persian Gulf just north of Bahrain.

1. Thanks to the shallow nature of these bodies of water they heat up during the summer season with average sea surface temperatures in the upper 80°s.
2. In fact, the hottest sea surface temperatures ever recorded anywhere in the world have been 98° in the Persian Gulf and 96° in the Red Sea.
3. Data compiled by the British Met Office (in its ‘Tables of Temperature, Relative, Humidity and Precipitation for the World: Part 4; Africa and the Indian Ocean’, 1967) for Boosaso (formerly known as Bender Caasim), Somalia between 1934-1946 indicate an average dew point of 83° at 2:30 p.m.

during the entire month of June (104° air temperature with 61% humidity). Obviously, some days are even hotter and more humid (the record June high for the period was 113° and the record low 78°). Assab, Eritrea has an average June afternoon dew point of 84°.

The absolute highest dew point recorded in the region and therefore the world (of which I am aware) was 95° at Dhahran, Saudi Arabia at 3 p.m. on July 8, 2003. The dry bulb temperature stood at 108° at the time, so theoretically the heat index was 176°. Sharjah in the United Arab Emirates (UAE) apparently once recorded a dew point of 93.2° (date unknown) according to ‘Weather Climate Extremes’ Army Corps of Engineers TEC-0099 report.

KUDOS: Thomas Schlatter of NOAA for USA dew point records and Dr. Adnan Akyuz, North Dakota State Climatologist for Moorhead, MN information. The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

How do you explain dew point to a child?

At dawn, tiny drops of water often cling to plants and grass. This moisture is called dew. Dew forms in the night air through a process called condensation. Air contains water in the form of a gas called water vapor. In the evenings, when warm, moist air passes over cool surfaces, the air cools down.

1. The water vapor in the air begins to condense, or form into small drops.
2. The drops cling to cool surfaces such as leaves, flower petals, and grass.
3. The temperature at which this condensation begins to happen is known as the dew point.
4. Dew usually forms on clear nights when the air is calm.
5. Dew can form on any surface that is cool and exposed to the sky.

It often forms on the ground and on plants because these things usually cool faster than the air. For the same reason, dew often collects on the tops of cars. The time of night when dew begins to form is called dewfall. Dew can help plants if they are dry.

What happens if dew point is higher than temperature?

Thus when the dew point temperature and the air temperature are the same, the air is said to be saturated- the air cannot hold any more water. So to summarize, if the dewpoint is the same or higher than the current temperature, then dew (or fog) will occur.

What is dew point when raining?

The dew point is the temperature at which the air can exactly hold the amount of moisture present. When raining, at any given temperature, the atmosphere can hold so much water vapour. So the dew point is equal to the room temperature.

What does dew point mean in oil and gas?

How is hydrocarbon dew point defined by the industry? – Hydrocarbon dew point (HCDP) indicates the temperature at which heavy hydrocarbon components begin to condense out of the gaseous phase when the gas is cooled at constant pressure. It’s sometimes referred to as “hydrocarbon liquid drop-out”.

1. Therefore, a higher HCDP normally indicates a higher proportion of heavy hydrocarbon components.
2. This is an important parameter for pipeline operators: if the natural gas contains a high proportion of heavy hydrocarbons there is a greater risk of liquid condensate forming in the pipeline.
3. The HCDP is defined as the series of matching pressure and temperature points at which hydrocarbons condense into liquid from a natural gas mixture.

It is typically displayed on a phase diagram (see below) as a function of gas pressure and temperature, for natural gas with a given composition. The dew point line divides the two-phase gas-liquid region and the single-phase gas region. Two dew point temperatures are possible at a given pressure and two dew point pressures are possible at a given temperature. Typical Water and Hydrocarbon Phase Envelopes for Transmission Quality Natural Ga This phase envelope phenomenon provides for behavior known as retrograde condensation. The word “retrograde” means moving backward and this phenomenon was given the name because it is contradictory to the phase behavior of pure components, which condense with increasing pressure and/or decreasing temperature.

The maximum pressure at which liquids can form is called the cricondenbar, and the maximum temperature at which liquids can form is called the cricondentherm. Note that given the shape of the phase envelope, the measurement of hydrocarbon dew point and potential hydrocarbon liquid is usually carried out at a pressure between 25 and 30 bar (ideally 27 bar) where liquid drop out occurs at the highest temperatures.

When condensate forms from a gas mixture, the distribution of hydrocarbons changes so that the liquid phase becomes enriched in the heavier components while the gas phase becomes depleted of these heavier components. As the gas is cooled below its original dew point temperature, the entire dew point curve shifts cooler for the remaining gas phase that is now depleted in heavier components. Typical Phase Envelope for 3 Stages of Natural Gas