# Tag Info

Accepted

### What is the range of possible atmospheric pressures on the surface of the Earth?

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 ...
• 5,892

### How are barometric pressure measurements traceable over centuries to 100 parts per million accuracy?

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 ...
• 439
Accepted

### Pressure as a function of altitude

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 ...
• 13.9k
Accepted

### Temperature change in Earth atmosphere models?

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 ...
• 567
Accepted

### How are low pressure zones tracked across the ocean?

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 ...
• 13.9k

### What is the inverted barometer effect?

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 ...
• 1,361
Accepted

### Why do certain areas on Earth have a higher or lower air pressure at sea level?

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 ...
• 20.4k

### How are barometric pressure measurements traceable over centuries to 100 parts per million accuracy?

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 ...
• 1,181

### How are barometric pressure measurements traceable over centuries to 100 parts per million accuracy?

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 ...
• 20.4k

### How significant is a 5-10 mb drop in pressure over a 20 minute period?

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 ...
• 1,787
Accepted

### Pressure as a function of altitude above 11 km

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 ...
Accepted

### Relationship between atmospheric density and atmospheric pressure?

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 ...
• 20.4k

### What does a floating mercury barometer look like? How does it work and how is buoyancy used?

A good place to start would be with Fortin barometers. They were "commonly used at meteorological stations to measure atmospheric pressure". The advantages of this type of barometer are its ...
• 20.4k

### Does temperature affect partial pressure of gas dissolved in water?

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, ...
• 20k

### What is the inverted barometer effect?

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)]...
Accepted

### How to identify low or high pressure area

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 ...
• 7,660

### When it is said that air moves from warm object to a cold object, how is it possible that air moves from high pressure area to low pressure area?

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 ...
• 101
Accepted

### What causes these periodic high-pressure blobs along the west coast of South America?

It's really not clear from their website what data source those maps are showing. They could be derived purely from surface observations, purely from model output, some atmospheric analysis ...
• 3,133

### How closely related is surface air temperature to pressure?

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 ...
Accepted

### Can strong winds significantly lower ocean surface levels, or is it really the static pressure differences?

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 ...
• 14.7k

### How does MSLP change with elevation? trying to interpolate MSLP

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....
• 8,307
Accepted

### Why does air subside in the Eye - the lowest pressure area of a tropical cyclone?

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 ...

### Pressure as a function of altitude above 11 km

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 ...
• 233

### Why is the Atlantic anticyclone an area of high pressure if it's the warmest spot on the planet?

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 ...
• 740

### How are barometric pressure measurements traceable over centuries to 100 parts per million accuracy?

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. ...
• 131
Accepted

### At what point is the atmospheric pressure considered to be high or low?

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 ...
• 8,307

### Pressure as a function of altitude above 11 km

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 ...
• 121

### Why do certain areas on Earth have a higher or lower air pressure at sea level?

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) ...
• 2,137
Accepted

### Why do meteorologists use DM and equal height surfaces for some maps?

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 ...
• 7,660