# Tag Info

17

Presssure at the Mt. Everest summit has been measured to be 253 Torr (337 hPa). http://jap.physiology.org/content/86/3/1062 Pressure at the Dead Sea as high as 1079 hPa is reported in Fig. 12 of this reference: http://isramar.ocean.org.il/isramar2009/DeadSea/Hecht&Gertman_2003_DS_Climate_Chapter4.pdf As far as at sea level, 870 hPa was measured for ...

17

Mark's answer about mercury barometers is correct - but it is not the complete story. Barometers were initially constructed using water, not mercury, on the manometer principle. Water is lighter than mercury, so a water barometer requires a 10.3m tube. 1mbar is therefore roughly 1cm, and 0.1mbar measurement is clearly trivial using a ruler with 1mm ...

13

The reported pressures are sea level pressure. For stations not at sea level (most of them), they can be corrected to sea level through use of the hypsometric equation. The reason the values are reported as sea level pressure is so that pressure values between stations can be interpreted in meaningful ways. See for example a typical sea level pressure ...

11

There's some kind of explanation about the units under the picture. The formula is based off the average temperature in degrees Celsius (measured over the entire year, and the entire Earth), which is 15.04 at sea level, and the temperature decreases by 0.00649 degrees every meter above sea level (the average lapse rate). The formula is 'valid' until 11 ...

10

It is a combination of points 1,2 and 4. Ships Ships can provide observations, but they are generally confined to shipping lanes rather than distributed all over the oceans. NOAA operates a volunteer observing program and you can find recent ship obs here. The ships can report location, wind direction, wind speed, pressure, pressure tendency, air ...

9

In a barometer, you have a tube submerged in a fluid, with a vacuum at the top. If air pressure is low, the fluid can drain out of the tube, letting you read how much lower the air pressure is than some reference value. So, the height of the fluid in the tube goes down as air pressure goes down. The "inverted barometer" is, in my opinion, much easier to ...

9

By way of analogy consider a hot air balloon. The balloon encloses some air. As the air is heated, via massive gas burners, the air in the balloon becomes less dense compared to the air outside the balloon and eventually the less dense air in the balloon rises, lifting the balloon into the air. Atmospheric air in contact with the Earth does the same thing. ...

9

A mercury barometer is a simple, easy-to-build barometer that turns the problem of calibrating a pressure standard into one of calibrating a length standard. Accuracy of length standards has long been a concern of merchants and those regulating them; in 1692, the standard would probably have been a brass prototype yard in the possession of the Royal Society....

6

I don't think they are using that level of accuracy for the old readings. Reporting pressure, in hPa, to one decimal place is being done for recent measurements. There are no values given for very old readings. As for the record reading of 1053.6 hPa for 1902, I suspect that is a mathematical conversion of a reading that was most likely recorded in inches ...

6

On the synoptic scale (thinking along the lines of cyclones, weather fronts etc.), then that's a pretty significant drop in that amount of time. A bomb or explosive cycogenesis in meteorological terms is defined as a drop of at least 24mb in 24 hours, so your observation easily fits this description of being a significant rapid pressure change. There's a ...

5

Those formulas are based on an assumption that the pressure is hydrostatic and the ideal gas law. The example given is limited to 11km but uses the tables from the U.S. Standard Atmosphere which actually go up to $1000$ km. Starting at Page 58 one can find values for pressure density and temperature above 11km.

5

There are two fundamental gas laws that need to be understood: Boyle's Law which states ${P_1.V_1 = P_2.V_2}$ From this formula if volume increases pressure decreases and vice versa The second law is Charles's Law which states ${V_1/V_2 = T_1/T_2}$ or ${V_1/T_1 = V_2/T_2}$ This law states that if the temperature increases there must be a ...

4

Because you specifically asked about winds and pressure, there is a fairly applicable rule of thumb. It's called Buys Ballot's Law. Basically, if the wind is to your back (coming behind you), and you're in the Northern Hemisphere, generally low pressure is to your left and high pressure is to your right. This graphic from http://www.maiamarinelli.com/ ...

4

The inverted barometer (IB) is a static (isostatic) response of the oceans to atmospheric pressure. The basic equation is IB = -(change in pressure) / [(seawater density)*(acceleration due to gravity)] Its an inverse relation i.e. with increase in pressure the sea level goes down and vice versa. In simple terms, 1 mbar decrease in atmospheric pressure with ...

4

have always been under the impression that if a gas is in equilibrium between its gaseous and aqueous forms, that it will always have the same partial pressure in the air as in the water. For example, both air and air saturated seawater have a pO2 of 21.227 kPa (101.325 kPa x 20.95%). That's a very bad impression, and your example is just not the case. ...

4

You are correct that air generally moves along the surface from high pressure towards low pressure (not directly, but deflected due to the coriolis effect). However, this does not imply that it is moving from a colder area to a warmer area. And, there is nothing contradictory in a cool air mass moving horizontally to displace a warm air mass. Extratropical ...

3

You have opened a very large can of worms. You will need a larger can to get them all together again. The problem is time lag. Let's do some thought experiments: It's dawn in the desert. Right now the bottom of the atmosphere is cool. Sun heats the dirt, and the dirt heats the air. Air expands some. But the air above it is lazy about getting out of ...

3

I will just talk about an already formed tropical cyclone. Converging winds spiral in (counterclockwise in northern hemisphere) over the warm ocean waters towards the central low pressure area of the eye. At the eye they spiral upwards, taking the warm, moist ocean air high into the atmosphere. As it reaches cooler elevation, the air releases its latent ...

3

The original description of the US. Standard Atmosphere 1976 turns out to include much more and detailed information than the Wikipedia article. I've now, finally, got it working using the fixed variables $H_b$, $\rho_b$, $T_b$ and $L_b$, which determine the standard height, (air) density, temperature and lapse rate at layer $b$, respectively. A sufficient ...

3

The explanation for the wind effect on water level at the coast is basically the same as for upwelling circulation. In an upwelling situation, the winds flow parallel to the coast and generate upwelling dynamics: surface Ekman balance is setup (in deep enough waters) with water transport being to the right (left) of the wind in the northern (southern) ...

3

So the Mean Sea level pressure is defined (simply) as the pressure of the station, corrected to sea level. However, methodological problems occur over terrain, such as assumptions that may not be true. A common method used to correct the pressure is called the barometric equation. One assumption, for example, is that the mean temperature of the previous 12 ...

3

How are barometric pressure measurements traceable over centuries to 100 parts per million accuracy? To compare records of barometric temperature, this standard doesn't necessarily have to be met. Recording barometric pressure to 100 parts per million precision has been possible for centuries because it's reasonably trivial to observe movement of the level ...

3

Usually when you hear someone say "high" or "low" pressure, it is an abbreviated way of saying "local maxima" or "local minima." And usually that pressure is the Mean Sea Level Pressure. By that definition, it is a singular point. But if you want to cover an area, you can probably reference a gridded dataset and plot ...

2

There doesn't seem to be central reference for standard temperature and atmospheric pressure at high altitudes. Below is the code I wrote after combining two resources that can be found in the comments. This C++ code calculates standard atmospheric pressure all the way up to 86km. float getStandardPressure(float altitude /* meters */) //return Pa { ...

2

There are entire chapters dedicated to this topic in physical geography and meteorology books; I doubt we could even scratch the surface here. But in addition to what Fred mentioned (good stuff, btw) there are two polar highs and the equatorial low, which are thermally produced. That is, the polar highs are high pressure because it's really cold and cold ...

2

Great question! First, let's look at typical data: here are the 1981-2010 Reanalysis mean and standard deviation: So looks like the mean 500 height in September for Wisconsin ranges from about 571-580 Dm, with a standard deviation of 36-42 Dm. These are mean pressures, not lows or highs, so already, not that far off your low. If (a big if) meteorological ...

2

The Bermuda high is centered near the horse latitudes, where air from the tropical Hadley trade wind cell is sinking. This forced sinking of air can dynamically contribute to high pressure even if the air is warm --- warm air can be forced to sink against its own buoyancy in a Ferrel-type circulation. But the Bermuda high is helped thermally too, at least in ...

2

First, yes, DM does appear to be decameters (though Dm would be more proper). D was actually the abbreviation I was taught for deca in grade school 20 years ago, but it appears da has become the official standard prefix now, perhaps because it was confused with deci (d). They also list the spelling deka instead of deca as well, perhaps for similar reasons (...

2

When you look on meteorological maps the "surface pressure" is actually the reduced MSLP (mean sea-level pressure) value. See this NWS page for more info. So whatever height the sensor is at above the ground, they regardless compare that height back versus the sea-level to report the pressure. I always figured barometers were sited along with the main ...

2

fracture formula What is the method of injection and fluid you are using? Apply a leak off test to the formation after drilling out casing shoe and your 5-10m into open hole. I’ve attached two links that may be helpful. formation fracture pressure a list of methods There are also plenty of apps for you’re ...

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