Atmospheric Pressure above Warming Surface | IRWC 20240719
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- Опубликовано: 5 сен 2024
- If the surface temperature increases 2K, what would happen to air pressure? This is a new perspective to study climate change.
So far, almost all reports on climate change have been focused on global mean surface temperature, or GMST for short, but it would appear nobody has mentioned air pressure near the surface. Does the pressure change with the surface temperature at all? If so, then how? Today, I am going to discuss this topic.
4.Temperature is directly associated with heat or cold. That’s why it seems more effective to draw peoples’ attention to global warming by using temperature, rather than, say, air pressure, mean-distance of freedom, although they are thermodynamically dependent, or even equivalent.
5.Indeed, would you ask a stranger, “What is the local air pressure today?” He or she might roll their eyeballs, as if they met someone from Mars.
6.Not only are our bodies insensitive to air pressure, but also their units seem too many. Atmosphere, bar, Pascal, Torr, PSI, mercury height in mm or cm, and so on and so forth.
7.To be frank, I still have trouble to convert one unit from another without googling them from time to time. I hope you wouldn’t mind going through these units today.
8.First, the unit for pressure in System International is Pascal, or 1 Newton per square meter. From the unit, we know pressure, by definition, is the force per unity area. By the way, Pascal was also famous for the Pascal Triangle when you study binomial theorem in high schools.
9.If you use Pascal for the atmospheric pressure near sea-level, then you would have to use a huge number, 101,325. Some researchers also used hecto-Pascal=100Pa for no obviouse benefit, at least it seems to me.
10.By way of contrast, this number would be simply 1 if you use Atmosphere, or Atm for short, as its unit.
11.Using mercury in tube with one end closed, you can create a vacuum of height 76 cm near the sea level. That’s way 1 atm =760 mm of mercury.
12. Next, Torr is a unit of pressure which is equal to 1 mm height of mercury. For this simple reason, 1 Torr=1/760 Atm or 101,325/760, about 133, Pascal. Hence 1 Torr is close to 133 Pa. I could be argued that mercury-in-tube was often used as a convenient pressure gauge before electronic device, such as Pirani gauge, was introduced. Still, vacuum is still measured in Torr, rather than Pascal.
13.Finally, if you perfer to pound and inch, then you must know 1 pound per square inch, or PSI, which is equal to 6895.76 Pa.
14.OK. Return to our topics. How to relate air temperature to air pressure? More specifically, what would happen to pressure if the global mean surface temperature increase 2 degree C or 2K?
15.According to ideal gas law inside a thermally insulated container,
Where P is pressure, V volume, T temperature, n mole number, and R is a universal constant. Because gas density is mass per unity volume, and molar number equal to mass divided by molar mass, we have
16.It is apparent pressure is proportional to temperature if gas density is kept constant. For air, the mean molar mass is close to 28.96 g.
17.One may ask: how can you assume air density is a constant near the surface? Well, this is what the earth has been trying to achieve endlessly for 14 billion years, otherwise the oceans would be boiling during sunny days.
18.Using this simple idea, if the temperature near the surface increases by 2 degree C from 288 K to 290K,=, then the air pressure would increase to 102,028 Pascal, by adding 702.6 Pascal! That’s is certainly not a small number, comparing with the 1.5 K anormaly in the GMST.
19.Nevertheless, this is not a serious problem at all as it happens every day and night. Because air has its freedom to move,. It can freely move in space vertically or horizontally, depending on pressure difference and temperature gradient.
20.As hot air has been replaced by relative cold air, the surface is cooling. That’s to say, the mean surface temperature can hardly be changed because only parts of the surface can be heated up by the sun. It is rather simple, isn’t it?
21.The vertical and horizontal movements of air currents are called convection and advection, respectively. Under the present air pressure near the surface, namely, 760 Torr, or 1 Atm, or one thousand and one Pa, thermal radiation by the surface is vertually zero, as I proposed last year.
22.That’s is how weather changes, which can be, for a short period of time, predicted by the numerically solving the Navie-Stokes equation, known and CFD, computational fluid dynamics, which is basically a variation of Newton’s second law of mechanics.
Thank you for your insightful video on the relationship between surface temperature and air pressure. Your points on how temperature affects pressure are intriguing, and I’d like to add some additional thoughts that might help refine our understanding of this relationship.
**Local vs. Global Effects:**
1. **Local Temperature Effects:** You correctly noted that increasing local temperature generally leads to a decrease in air density, according to the ideal gas law. For a localized scenario, if we assume that the volume remains constant, this results in a decrease in pressure.
2. **Global Perspective:** On a global scale, however, the situation is more nuanced. The Earth's atmosphere has a fixed total mass and surface area. When global temperatures increase, the atmosphere expands vertically. Despite local decreases in density due to temperature increases, the overall atmospheric mass and surface area constrain changes, which stabilizes surface pressure.
**Mathematical Considerations:**
According to the ideal gas law:
P = (ρ * R * T) / M
Where:
- P is pressure,
- ρ is density,
- R is the universal gas constant,
- T is temperature,
- M is the molar mass.
The relative change in pressure (ΔP / P) can be expressed as:
ΔP / P = Δρ / ρ - ΔM / M
In your example, you assumed a 1.5°C increase in temperature, which is approximately a 0.5% increase relative to an initial temperature of 288 K.
- **Density Change (Δρ / ρ):** A 1.5°C increase in temperature causes a decrease in density. For a 0.5% increase in temperature, the density change is significant locally.
- **Molar Mass Change (ΔM / M):** The change in molar mass due to increased CO2 concentration is relatively minor (about 0.037%).
Combining these factors, the dominant effect of increased temperature is a decrease in density, which would lead to a decrease in pressure locally. However, globally, the total atmospheric mass and Earth's surface area help stabilize pressure changes.
**Conclusion:**
Local temperature increases lead to noticeable changes in pressure due to density reduction. However, the global atmospheric pressure is moderated by the overall mass and surface constraints. This distinction between local and global effects is crucial in understanding the real impact of temperature changes on atmospheric pressure.
Looking forward for any clarifications or comments.
Thanks a lot. What a systematic consideration! I will make another video soon. Just a few remarks here.
You wrote: "A 1.5°C increase in temperature causes a decrease in density". According to molecular kinetic theory, an increase in temperature is equvivalent to increase the mean speeds of moving molecules and hence reduce the mean distance of freedome. This implies that inter-molecular collissions becomes more frequent in the first place. It also means air pressure
increases, irrespective of the weight of air molecules above.
Yes, the distinction between local and averaged golable effects is essential.
The distinction you made is important. Local air pressures oscillate about the global mean air pressure calculated by the total air weight divided by the surface area. Still, whehter the total atmospheric mass is a constant is another basic issue. So for, it would appear ALL quantities are periodically changing, such a dynamic equilibrium is intriguing indeed.
Many times the best solutions are simplest ones. Great point!
Thank you very much Dr Yong, we are learning alot from you.
PhD Ned Nicolov has done extensive research about this.
Yes, he also considered other planets.
Hi - would be interested in your thoughts on the thermalisation of greenhouse gasses as discussed in Tom Nelsons latest podcast #232.
That is the Tom Shula, Markus Ott presentation. Definitely the same area of interest.
The atmosphere is a container without a lid, therefore the volume is infinite; trying to apply P V =n R T to the atmosphere is absurd.
In a rigid, sealed container filled with gas, a pressure gauge fitted to any point on the top wall of the tank will give the same reading as one fitted to the bottom. That is not the case with a tank filled with liquid. Try it out on your car tire, if you want.
Thanks,well explaind🔎💧
Sometimes the solution is simple. Brilliant. Now I have a question. Mercury is also used in temperature gauges. But in a closed tube. Meaning it has vacuum in it. Since an air pressure gauge is in an open tube the expanding mercury by energy uptake is affecting the pressure reading. That means any mercury pressure reading may vary. I think heating the tube will show that.
The inventors for the two instruments might have considered the thermal expansion coefficient of mercury.
Excellent summary of confusing pressure units. Right now the pressure at the nearby airport in 29.96 *inches* of mercury and falling. This is 761 mm of mercury or 1.0013 Atm. I prefer to use atm in my calculations, because I know what it means. At our elevation of about 130 m pressure readings should be slightly lower than 1 atm.
The temperature is 99 F or 37 C. We are already into the hottest part of the day. The prediction was for 104 F. The predictions are always a few degrees higher than the actual temperatures. Headlines scream "record temperatures predicted", and few ever check actual temperatures for systematic bias. The actual record was 118 F set in the 1930s.
"Up near the northern border of the US we have already seen more than 3 C of warming. This has brought milder Winters and more humidity. We had a wonderful storm last week that dumped buckets and cooled temperatures. While the rain was pouring down I checked the weather report: 10% chance it might rain. There is another storm coming in tomorrow or Monday. Two storms in a parched desert in July would be a minor miracle. The weather report says 5% chance of precipitation. Looking out the window, I would rate it as 100% by Monday evening with cooler temperatures coming Tuesday.
Thank you for infoming us your local air pressure and temperature. In Australia, heavy rains and floods show up after a large scale bushfires. It appears natural you get two storms in a parched desert. I think the earth wouldn't allow an extreme weather for too long.
Perhaps you would like to watch my another talk on Tim Palmer. Because you mentioned "10% change it might rain" and "5% chance of precipitation" that sound the typical phases used in ensemble numcertical weather prodictions introduced by Tim. He would be sad if he could read your comments.
It is about the same time the next day. The prediction was for 108 F or 42 C, but the hourly predictions only went up to 106 F. An hour ago the temperature was 98 F, and at the moment it is 97. So the predicted temperature was high by 10 F. indicating a very serious bias. The sky is overcast, indicating water vapor condensing to water droplets above. The probability of rain tomorrow was at 5%, then it was lowered to 3%, and now it has risen to 9%. The pressure at the nearby airport is 29.83 *inches* or 758 mm of Hg or 0.9974 atm.
The name Fred Hansen is familiar. Back in the day when I was still on speaking terms with some climate scientists, someone mentioned his paper on the atmosphere of Venus. I thought I had read it, and rejected his conclusions. Later on I realized the paper I read was in a completely different journal put together by Carl Sagan in the 1960s. I believe it was called "Planetary Atmospheres". Then I glanced through Hanson's paper and realized he had neglected to reverence this prior work. Both papers made the same fatal mistake: assuming the atmosphere of earth and Venus were created in their modern state: a complete rejection of evolution.
I will have a look at your video on Hansen. I am interested to hear what you think of him.
Since you can find both measured air presssure and temperature, is that possible for you find several data in which the pressure and the temperature were simultaneously measured? Say, (761 mm, 99 F), (758 mm, 108 F) etc. ? I wonder whether the pressure was measured at the same air temperature. Thank you.
Migraines are made worse by rapid changes in air pressure and humidity!
Thank you to tell us. Or could it be due to chnages in air temperature?
Aren't Boyle's laws, the STP that I learned in High School, something as significant as the Pythagorean Theorem or Pi? Same as ideal gas law.
I got a little lost on the math. Atmosphere, PSI, mmHg all work for me. Simple, intuitive.
Changing water vapor content significantly affects air density. A 90F air-mass at 5% relative humidity colliding with a 90F air-mass at 50% relative humidity regularly produce spectacular dry-line thunderstorms, the dry air acting like a hot cold-front.
I would have thought that warmer air would result in lower pressure.
Ideal gas equation says otherwise
PV = nRT
Pressure is directly proportional to temperature.
@@cecaloather8701 ...within a container. A parcel of atmosphere is not contained.
Indeed, Boyle's law, PV=constant , is relevant to this discussion, assuming the surface temperature is fixed. When the surface temperature changes, however, PV becomes a different constant.
Depends on where you take a reading & constraints.
Intense low pressure systems like hurricanes or typhoons crossing techtonic plate boundaries correlate to uplift thus earthquakes so it may be possible to forecast an earthquake.
Air pressure differences are the driver for weather phenomena, such as wind and rain, but whether they can be correlated with earthqueakes remain to be explored.
i have been telling my wife for years that, i can tell by the air pressure how it effect's the weather and my body
I enjoy your channel; and I align closely with your opposition to much of published atmospheric science. But, I must disagree with your use of the universal gas law with respect to Earth's mean surface pressure and temperature. Earth's surface pressure is independent of temperature. Only the mass of the atmosphere, surface area and gravitation are needed to determine the mean surface pressure.
I look forward to your future submissions. Keep up the good work.
Thank you for your comments. Indeed gas law is valid for thermal equalibrium in a confined space. It is often assumed some basic laws are approximately valid for so-called "local thermal equalibrium ". That's why the ideal gas law is used here as an estimate.
@@yongtuition Thought experiment: Select a pipe with an inside cross-sectional area of 1 square inch. Set a 1,000 mile length of the pipe vertically Leave the top end open. Leave the the bottom open to come to pressure equilibrium, 14.7 psi. Then close the bottom of the pipe. The pipe now has 14.7 pounds (mass) of air in it. Heat the pipe and the air inside it to 1,000 degrees, Fahrenheit. The pipe still has 14.7 pounds (mass) of air in it. If you measure the pressure at the bottom of the pipe, it will still be 14.7 psi. The distribution of gas density as a function of height (altitude) will of course have changed.
Please accept my remarks as a form of peer review and not a criticism of your work.
@@firstlast-ty4di If the gas as a whole is moving, the measured pressure is different in the direction of the motion. The ordered motion of the gas produces an ordered component of the momentum in the direction of the motion. We associate an additional pressure component, called dynamic pressure, with this fluid momentum. The pressure measured in the direction of the motion is called the total pressure and is equal to the sum of the static and dynamic pressureas described by Bernoulli's equation
@@stigsrnning6459 Your statements are valid. In my thought experiment, I included only high-order factors: mass, gravity, and area. Low-order factors include temperature, coriolis, centripetal, inverse-square change in gravity, relativistic effects of velocity differences at different height, and others. If one applies any realistic combination of the low-order factors, less than a 1% change will be found.
Not to mention that pressure can be Gauge or Absolute :)
The basic issue here is whether the surface air pressure can be described as the air weight above the surface or molecular collisions based on thermodynamics.
Barometric pressure? We hear hi and low pressure systems. Hurricans have very low barometric pressure in the eye ? But what does it mean? Why can't we use one standard measurement? 😱
Good questions. I have been thinkg about them lately. Please stay turned.
I don't think air pressure is affected by temperature. The pressure at the surface is purely a function of the mass of air above it, which cannot change. The atmosphere is not enclosed in a box. The atmosphere may expand as it gets warmer, and if anything, this would cause a slight decrease in pressure due to the inverse square law for gravity.
you have gravity which is pushing the atmosphere down, so it is the same as an enclosed box. And you have basic thermodynamics equations. Additionally, you have many other factors but this one it is pretty much common sense in some to me unknown value.
Gravity is simple Galilean relative motion. The earth is approaching- expanding at 16 feet per second per second constant acceleration- the released object. “The Final Theory: Rethinking Our Scientific Legacy “, Mark McCutcheon for proper physics including the CAUSE of gravity, electricity, magnetism, light and well..... everything.
@@davidrandell2224 gravity is a force pushing atmosphere toward earth.
@@hrvojelasic5794 Gravity is based on size and expansion not mass and attraction. Read first, then comment.
you will find that the hottest and coldest temperatures recorded are not at the poles or the equator. the atmospheric pressure has been recorded at over 3kPa above average and also well below average. the hot air which rises from the equator creates a low pressure (and cooling) and as that air cools with increasing altitude it then falls over the tropics of cancer/capricorn. that "cold air" under high pressure is what results in high temperatures and resulting deserts along those latitudes.
This just confused me. I learnt nothing.
Only that our atmosphere transports heat by convection and advection to equalise pressure?
Pressure and temperature are not linked 😜 😂
"but it would appear nobody has mentioned air pressure near the surface" Easy to find that there have been many such studies. At least this site understands and accepts that the earth is warming and the primary forcing is CO2.
If you don’t know what gravity is don’t call yourself a physicist, astronomer, cosmologist or indeed even a well informed human being.
No one knows what gravity is, only how it behaves. If you do know what causes it, please write up your hypothesis and collect your Nobel Prize.
@@fredneecher1746 Gravity is simple Galilean relative motion. The earth is approaching- expanding at 16 feet per second per second constant acceleration- the released object. Read first, “The Final Theory: Rethinking Our Scientific Legacy “, Mark McCutcheon for proper physics including the CAUSE of gravity, electricity, magnetism, light and well... everything, then comment. Public/ public knowledge for 22 years; try to keep up.
@@fredneecher1746Newton only described its behaviour. There has been a lot of progress since then.
@@davidrandell2224I think that is more misleading than enlightening. The Earth doesn't expand.
What you describe is Einstein's equivalence principle, but you are not describing it well.
@@davidwuhrer6704 A proton is a collection of 1836 expanding electrons and add a bouncing expanding electron makes a hydrogen atom. “G” calculated from first- the hydrogen atom- in 2002. All atoms and atomic objects are expanding at 1/770,000th their size per second per second constant acceleration. Multiplied by earth’s radius equals 16 feet etc: d=1/2at^2. The earth’s surface is literally, physically the floor of Einstein’s cabin. Really simple. Kepler’s 3 ‘laws’ are energy free, mass free, force free and inverse square ‘law’ free. ALL orbital equations likewise: Newton does not apply. ALL Standard Theory/Model irrelevant. Any accelerometer- slinky, water balloon or phone app- experiment Proves the earth is expanding. Progress.
this topic is too political for my feed
It's physics. Physics doesn't care about what ought to be, only what is. Politics cares about what ought to be. Which not all agree about, but the facts are what they are.