does altitude effect you differently below the equator?

I would think that elevation is elevation, regardless of where you are. Humidity might have affected you. I don't know, but I doubt it was your southern latitude.

There isn't a difference between the Northern and Southern Hemispheres, but there is a difference between the continents of North America and South Africa. North America sits on the Pensky continental plate, which elevates the entire continent (including the surrounding oceanic waters) 2,470 feet above sea level. So, when you are running at 5,500 feet in Colorado (or in Nevada or Arizona), you are in effect running at 7,970 feet.

In South Africa, by contrast, 5,500 feet elevation is 5,500 feet, as the entire continent rests on a sea-level plate. It makes sense that running in South Africa at the "same" elevation would seem easier.

Air Pressure: The Effects of Altitude, Latitude and Season

by Ward Hobert

A combination of centrifugal force and temperature differences make the troposphere thickest at the equator, 10 to 11 miles. It is only 5 to 6 miles thick at the poles. Due to lower temperatures the troposphere is more dense at the poles, and the net result of all contributing forces and factors is that air pressure is pretty much the same planet wide at sea level. At high altitudes this is not true.

Since the air layer over the earth is thinner at the poles, any upward movement from the planet's surface passes through a greater portion of the air layer than the same movement would accomplish at the equator. Thus, for higher altitudes, air pressure at high latitudes is lower than it is at low latitudes.

We can not quantify this effect until we address seasonality. In the winter the air mass over the poles cools and contracts, and the thickness of the planet's local atmospheric layer decreases. (Of course, the opposite pole is experiencing summer and its air layer is expanding.) Thus, in winter at high latitudes and high altitudes air pressure is further depressed.

Now, to quantify: consider the altitude at which air pressure averages 0. 5 atmospheres. On Mt. McKinley, 63: N latitude, this altitude is, on the average, 18,400 feet in mid-summer, and 16,800 feet in mid-winter. In the vicinity of Mt. Everest, 30: N latitude, this altitude is 19,400 feet in mid-summer, and 18,850 feet in mid- winter.

At the summit of McKinley, 20,320 feet actual altitude, the average air pressure in mid-summer is about 0.453 atmospheres, which would correspond to a Himalayan summer altitude of 21,650 feet. In winter the summit pressure for McKinley, 0.420 atm., corresponds to a Himalayan winter altitude of 22,800 feet, and a Himalayan summer altitude of 23,460 feet.

Chimborazo, 20,700 feet actual altitude, is essentially on the equator ( 2: S latitude) and so its summit pressure of about 0.472 atm. does not vary much seasonally.

Most of the information supplied here came from "The World's Great Mountains: Not the Height You Think", Terris Moore, American Alpine Journal 16:109, 1968.

For your information:

1 atmosphere = 760 mm Hg = 760 Torrs = 29.92 in. HG = 14.70 psi = 1.013 bars

I'm really tired, but let me just write down my thoughts for a second...

I know that there's an equatorial bulge, but if you measure everything with respect to sea-level aren't you making up for it? The ocean must be at more or less constant global pressure, or else it would all flow towards or away from the bulge (there is no net flow -- ocean currents swirl). I suppose as your altitude increases, the pressure may decrease at different rates depending how far you are from the bulge...

How about some alternative explanations -- could it just be more pollution in Colorado? Warmer or cooler air?

Here is an alternative explanation, you are fvcking stupid, and have never actually cracked open a science book.

more pressure in South Africa, thicker air (more Oxygen)

What about latitude?

The physical conditions in the different mountain massifs of the world depend on their latitude.

******************************************************

Altitude

Available Oxygen, Compared to Sea Level (average observed at 45 degrees latitude**)

0 feet (sea level)

100% (base for comparison)

5,000 feet

80 % of sea level oxygen per lungfull

10,000 feet

69% of sea level oxygen per lungfull

15,000 feet

56% of sea level oxygen per lungfull

18,000 feet

50% of sea level oxygen per lungfull

20,000 feet

45% of sea level oxygen per lungfull

29,000 feet

31% of sea level oxygen per lungfull

**The above figures are averages that apply only to the mid latitudes (45 degrees latitude, North or South). Oxygen available per lungfull also varies slightly by latitude as follows: you will gasp for air about 5 percent harder when climbing at 20,000 feet on Alaska's Denali (Mount McKinley) than when climbing at the same altitude in the Himalayas. Denali is at 63 degrees north latitude, the Himalaya at 28 degrees north latitude, and the Cordillera Huayhuash at 10 degrees south latitude. Denali rises to 20,320 feet but has the oxygen availability of a 23,000 -foot peak in the Himalayas.

At a given altitude, oxygen available per lungfull is highest at the equator (0 degrees latitude) where the atmosphere is deepest (such as at Mount Kilimanjaro, Africa), and lowest at the poles (90 degrees latitude) where the atmosphere is shallowest. The centripetal force of the earth's spin shapes the atmosphere (and the earth itself) into an "oblate spheroid", flattened at the poles and bulging at the equator.

************************

Although altitude is the most obvious determinant of barometric pressure and its resulting physiologic stress, other factors affect it, including:

* Temperature

* Weather patterns

* Latitude (distance from equator)

Decreasing temperature has the effect of lowering atmospheric pressure and increasing altitude-related stresses, an effect particularly common during winter months. Deteriorating weather is typically associated with lower barometric pressure and also increases the physiologic consequences of altitude. Latitude also exerts an important influence on barometric pressure. Because of a large mass of cold air in the stratosphere above the equator, the pressure at a given altitude at the equator tends to be higher than at distances from the equator. It can be expected, therefore, that the physiologic stress of a given altitude will increase as distance from the equator increases.

Here's a little trivia for everyone: Where is the closest point on earth to the Sun? Most would say the peak of Mt. Everest, but it's actually Mt. Chimborazo in Ecuador. Chimborazo is the tallest since it is located nearly on the equator, where the earth bulges the most. Chimborazo is 6,384,404 meters away from the Earth's center, where as Mt. Everest is 6,381,670 meters from the center. I did some climbing in Ecuador and Peru and had the pleasure of of seeing Chimborazo and many other peaks in the Andes. I didn't get the opportunity to summit Chimborazo, but I did summit Cotopaxi (19,388') which is only a few miles form Chimborazo.

Trollie McSockpuppet wrote:

There isn't a difference between the Northern and Southern Hemispheres, but there is a difference between the continents of North America and South Africa. North America sits on the Pensky continental plate, which elevates the entire continent (including the surrounding oceanic waters) 2,470 feet above sea level. So, when you are running at 5,500 feet in Colorado (or in Nevada or Arizona), you are in effect running at 7,970 feet.

In South Africa, by contrast, 5,500 feet elevation is 5,500 feet, as the entire continent rests on a sea-level plate. It makes sense that running in South Africa at the "same" elevation would seem easier.

well then wouldn't the air pressure also be raised to a point 2,470 feet. It would be the same thing as running at the same altitude. so it makes no difference whatsoever.

I just farted on you.

it only makes a difference if you run according to the pose method... my science show that gravity works in the opposite direction in the southern hemisphere, gravity then pulls you back, try one of my antipose clinics