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Questions tagged [humidity]

The level of water vapor in the atmosphere. Use this tag for questions about either relative or specific humidity.

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Which is drier, the Sahara Desert or the South Pole?

I would not be surprised if the answer is the South Pole, because it is much colder and the vapor pressure drops very quickly with temperature.
S. Kohn's user avatar
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3 votes
2 answers
314 views

At 100% relative humidity, why does the air still feels dry?

At 100% relative humidity, the dew point temperature is the same as the current temperature. One would probably conclude that water would start condensing on surfaces. But seems that is not always the ...
Koala Yeung's user avatar
2 votes
0 answers
121 views

Is there such a thing as a "warm wind"?

Sometimes, people say things like "It's only $5^\circ\mathrm{C}$ outside, but there is a warm wind, and it feels much warmer" (I live in Austria, a region where there are Föhn winds). I have ...
DominikS's user avatar
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2 answers
92 views

Why is U used for relative humidity in atmospheric measurement equipments?

RH is the symbol of relative humidity in many textbooks. But, in my experience, U is often used in atmospheric measurements. For example, Vaisala PTU300 means pressure, temperature and humidity. I ...
Oone's user avatar
  • 11
1 vote
1 answer
296 views

Why are eastern Oregon and southeastern Washington so dry?

Why are eastern Oregon, southeastern Washington and southern Idaho so arid, as compared to the humid and lush western Oregon and Washington? In Oregon and Washington there is quite an abrupt boundary ...
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1 vote
1 answer
440 views

Dew-point temperature and absolute humidity

I am looking for a reference (e.g. book, peer-reviewed paper) that asserts that absolute humidity is "equivalent" to the dew-point temperature. Such statement should be true, AFAIU. Online, ...
Yair Daon's user avatar
  • 113
2 votes
1 answer
421 views

How to calculate wet bulb globe temperature (WBGT) using only temperature and humidity?

Greetings fellow scholars, I'm trying to answer the question above because I've come across WBGT calculators like this one (https://www.climatechip.org/heat-stress-index-calculation) and I don't ...
Dt23's user avatar
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1 vote
1 answer
190 views

How to get specific humidity through absolute humidity and height above ground

I'm trying to make a weather simulator using the article Interactive Meso-scale Simulation of Skyscapes. It gives the formula for calculating the mean static energy: $$MSE_i = C_p \cdot T_i + g \cdot \...
w.ilia.m's user avatar
3 votes
0 answers
143 views

What is the "average relative humidity" of the Earth's atmosphere?

What is the current ratio of the amount of water in the Earth's atmosphere compared to its moisture storage capacity? I see values like "a half" or "70% on various web pages, but can't ...
David Bailey's user avatar
  • 1,018
1 vote
1 answer
68 views

Is good rainfall in the UK the result of being a small island surrounded by large moving seas, having mountains and trapped salt [closed]

If the mountains were levelled and salt removed would the country experience as much rainfall? Context Damp in houses: Salt absorbs moisture: think of plaster walls that grow mould from proximity to a ...
Steve Tomlin's user avatar
4 votes
0 answers
69 views

What is the definition for a hyper-humid area?

We can use the aridity index $\left ( ai = \dfrac{P}{PET} \right )$ to define arid areas. Hyperarid areas have $ai < 0.05$. Is there a similar threshold for hyper-humid regions? Would it be 20 (...
Pedro Alencar's user avatar
3 votes
1 answer
617 views

How to convert specific humidity ERA5 in kg/kg to g/kg or mm/day?

The specific humidity of ERA5 data is kg/kg, but some articles work with this variable in g/kg. How can I convert this? Or to compare with precipitation, evaporation, and other variables, how to ...
smi's user avatar
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2 votes
3 answers
4k views

ERA5 Single Level - Calculate relative humidity

for ERA5 hourly data on single level relative humidity can not be downloaded. However, dewpoint temperature is given and in the description it is stated that "combined with temperature and ...
Anna Wenning's user avatar
10 votes
2 answers
800 views

Is "humidity" the quantifiable metric for mugginess?

I've always described somewhere as "humid" if the air feels very moist and muggy. So, in the US, I'm thinking of places like Texas (e.g., Houston) and Florida (e.g., Miami). I would consider ...
student010101's user avatar
1 vote
2 answers
75 views

What are some reasons for Aridification

I an working on a Si-Fi world, and am looking for ways that an area would, over a long timescale, lose the majority of its water. I understand how the lose of vegetative cover due to climate changes ...
Zoey's user avatar
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3 votes
2 answers
2k views

Pressure vs Temperature effect on humidity

I am a bit confused about pressure vs temperature effect on relative humidity. I know that air density is decreased with altitude, which means that there is more "space" between air ...
Meir Tolpin's user avatar
1 vote
1 answer
115 views

Meterological measures -formula containing temperature, humidity, cloud, wind

I am looking for a meteorological measure (formula) of something which combines 2 or more of the following: temperature, humidity, cloud, wind, precipitation, UV I have searched, and for example, ...
maths's user avatar
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2 votes
1 answer
230 views

Is there a bigger diurnal temperature variation in the summer because of a greater humidity?

It seems there is a greater variation in temperature during summer than during winter (image: maximal and minimal temperatures in Britain - source). My hypothesis is that this is because there's a ...
Probably's user avatar
  • 297
18 votes
3 answers
6k views

Why would it be drier indoors during the winter vs the summer?

Yesterday during the day, inside my house it was 16% relative humidity. Outside it was 69% relative humidity and cold, around 35 degrees Farenheit. It is always 72 degrees Farenheit inside the house. ...
Tyler Durden's user avatar
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2 votes
2 answers
1k views

What is the difference between surface specific humidity and surface relative humidity?

What is the difference between surface specific humidity and surface relative humidity (it's wetter and dryer respectively)? The trends, according to the latest IPCC report, are opposite for the two, ...
Sergey Zolotarev's user avatar
3 votes
1 answer
148 views

What Pa level should I use when looking at Relative Humidity data from CMIP6 models?

I have downloaded a number of future simulations for a group of GCMs from CMIP6 for the variable Relative Humidity (hur). I chose the 100000pa level to view the RH data in panoply for the EC-Earth ...
matlabcat's user avatar
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4 votes
0 answers
100 views

How can I deal with unrealistic Relative Humidities being calculated using vapour pressure and saturated vapour pressure?

I am calculating RH (%) using this well accepted equation: $RH =e \times \frac{100}{es(T)}$ where $e$ is the vapour pressure and $es(T)$ is the saturated vapour pressure at temperature $T$. I have ...
matlabcat's user avatar
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3 votes
0 answers
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Incorrect relative humidity with SHT30 when comparing to dry and wet bulb calculation

I am attempting to calculate wet bulb temperatures needed for agricultural curing processes. I am trying to do this by inferring the wet-bulb value from relative humidity and dry bulb temperature. The ...
Hayden Eastwood's user avatar
2 votes
1 answer
561 views

How does a whirling hygrometer work, how does it differ from static dry/wet bulb thermometer, and how to obtain humidity from its readings?

Answers to my previous question How is relative humidity determined from a wet and dry bulb readings? provide equations for converting the two temperature measurements to a relative humidity. In ...
uhoh's user avatar
  • 7,070
1 vote
1 answer
960 views

How to convert Relative humidity (%) or Specific humidity (kg/kg) to Air humidity (mb)?

The model I use needs the data of Air humidity and unit is 'mb' (there is no other explanations about this variable), but now I only have two datasets and there are Relative humidity (%) or Specific ...
Gloam's user avatar
  • 19
3 votes
1 answer
185 views

Why does relative humidity drop if I open the window in winter? What about the temperature drop?

I understand that 40% rel. hum. at 0 °C is less absolute humidity than 40% at 20 °C. However, assume that we have 2$~m^3$ of air. Both are 40% humid at 20 °C. Now we exchange 1$~m^3$ with air that is ...
user250614's user avatar
3 votes
2 answers
1k views

How to calculate the specific humidity based on the saturated specific humidity?

I am using ERA5 data to drive the land surface model. One of the forcing required by LSM is specific humidity. We want to use the 2-m specific humidity. So how can I calculate the specific humidity ...
Xu Shan's user avatar
  • 171
8 votes
1 answer
1k views

Relative Humidity approximation from Dew Point and Temperature

I would like to find a formula to approximate RH based on known air temperature and dew point. I need the approximation to be valid at least between -20...+40 degrees Celsius. I read the accepted ...
Darius V.'s user avatar
2 votes
2 answers
2k views

What does supersaturation with respect to ice mean?

I've been reading about the Bergeron process, a process that generates much of the precipitation in the middle latitudes by generating ice crystals at the expense of water droplets. The part I don't ...
wheelix's user avatar
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8 votes
3 answers
327 views

How do the pros measure humidity?

I have used a wet/dry bulb setup to estimate humidity, and it appears that the Argentinian meteorological service uses one in Antarctica as well. Wikipedia sez: Humidity measurement is among the ...
uhoh's user avatar
  • 7,070
6 votes
1 answer
3k views

How is relative humidity determined from a wet and dry bulb readings?

The question What is the second thermometer in the image from the Esperanza Antarctic temperature record? shows what might be a wet/dry bulb setup. I've given one to a friend to measure humidity for ...
uhoh's user avatar
  • 7,070
1 vote
0 answers
32 views

Finding free humidity data

I am trying to find historical humidity levels (ideally in percentage format) across the globe divided by sub-country regions or more granular. The time granularity would be daily, but hourly would ...
map.apps's user avatar
3 votes
1 answer
139 views

What the humidity metric is hiding?

So I have been spending time in Moscow Russia which essentially records very similar climatic humidity to my home city of London. However in Moscow my throat is permanently dry, I need to consume more ...
Iain Watt's user avatar
1 vote
2 answers
538 views

Deserts and Humidity

How is that a general rule of thumb that less humidity equals more rain? Deserts don’t get much rain and humidity is also very low. Rainforests get a lot of rain when the humidity is very high so how ...
Ryan Amalfitano's user avatar
1 vote
1 answer
213 views

Humidity and Rainfall

Usually the higher the humidity the more rainfall we get like in the summer here in Asheville, North Carolina we get a lot of showers and thunderstorms in the summer from the high humidity but I saw ...
Ryan Amalfitano's user avatar
1 vote
0 answers
43 views

How does this calculate the water transport between crops in the webside?

click->http://gpe.letsgrow.com/ next click->moisture transport In the results of Moist transport through the crop, what is the relationship between crop height and diffusion, air movement, and total ...
Ning Mei's user avatar
1 vote
1 answer
93 views

Definition of Surface-based atmospheric duct

I am writing a literature review for a project and I have a problem. Namely, I cannot figure out the the condition required for surface-based duct to occur. Literature does not help either. In one of ...
Scavenger23's user avatar
4 votes
0 answers
52 views

Oscillating dew point throughout the year?

I was searching for the climate of Saudi Arabia and I noticed that the city of Abha (altitude of 7000 feet) has a "strange" behavior in its dew point, as numbeo suggests: https://www.numbeo.com/...
user17108's user avatar
3 votes
1 answer
1k views

How does total pressure affect relative humidity and how do I correct my hygrometer for pressure?

Obviously pressurized air can hold more water than regular air, so an increase in overall pressure would result in an inversely proportional decrease in relative humidity. However, I can't seem to ...
Curtis's user avatar
  • 151
9 votes
1 answer
19k views

How to calculate relative humidity from temperature, dew point, and pressure?

Is there a formula given the temperature, dew point, and pressure to find relative humidity? I have seen several calculators like this one, but I would like to know how to calculate this myself. I ...
ReinstateMonica3167040's user avatar
2 votes
2 answers
785 views

Can minimum relative humidity be greater than maximum relative humidity?

I am trying to calculate minimum and maximum daily Relative Humidity values given a min/max Specific Humidity and min/max Temperature. I found some equations here that work with the given variables, ...
joshk94's user avatar
  • 21
5 votes
1 answer
417 views

How to predict when contrails are likely to form over a specific location using public data?

I saw the image below used as a click-attractor to an unrelated story about tourism, but found a larger version here. Contrails, or water condensation trails happen when planes pass through the ...
uhoh's user avatar
  • 7,070
16 votes
4 answers
23k views

Why does warm air "hold" more moisture?

It is often explained that warm air holds more water because warmer water is less likely to condense. This and other explanations just seem to be circular arguments. If the warmer air picks up enough ...
Clark's user avatar
  • 261
7 votes
1 answer
359 views

How is the specific heat of a wet bulb determined?

I am quite new to the psychrometry and the study of humidity, and I'm currently learning about the dry-bulb wet-bulb thermometry. As far as my understanding goes, the wet bulb is connected to a source ...
Pritt Balagopal's user avatar
1 vote
1 answer
1k views

Water vapor content versus specific humidity

I am wondering the difference between water vapor content and specific humidity to determine the moisture availability in the atmosphere. Which one is more acceptable variable to determine the ...
Kay's user avatar
  • 461
5 votes
1 answer
2k views

How would I use data to find specific humidity and mixing ratio?

I keep reviewing this table to compare and contrast my results: The parcel of air is at 35°C and a relative humidity of 43%. I used this online calculator and it stated that with these two factors ...
yre's user avatar
  • 485
6 votes
1 answer
5k views

How to calculate humidity using outside temperature and outside relative humidity?

I would like to ask how to calculate the relative humidity that a heated indoor area would have using only outside temperature and outside relative humidity. I found the Relative Humidity Calculator ...
klarkson's user avatar
3 votes
0 answers
2k views

Is this an accurate simulation of a further south Australia with a filled lake Eyre?

I created this climate map based on a simplified Koppen Climate Classification map (shown below). In this scenario Australia is moved 10 degrees of latitude further south and the Lake Eyre basin is ...
VenusUberAlles's user avatar
2 votes
1 answer
105 views

Why a stratus cloud does not always reach all the way to the ground?

The surface of the ground at night cools down because of outgoing long-wave radiation. In my understanding the cooling of the surface also causes cooling of the adjacent air. If the air contains ...
jirikadlec2's user avatar
0 votes
1 answer
2k views

What is the mixing ratio of a cloud?

A cloud has relative humidity of 100% or more. Is it correct to say that the mixing ratio of a cloud is undefined? My reasoning is that dry air in a cloud is negligible therefore $w = \frac{x g}{ 0 kg}...
Reqbisha's user avatar
  • 339