The Weather On Mountains

The higher you are in the mountains, the lesser atmosphere pressure, the faster winds, and the colder air you find. Air pressure on the summit of Everest drops down to 300 mbar, the speed of the wind rises to 320 km/h, and the temperature is about -70 C. Even if you take lower mountains, the winds encountered there are still much stronger than those in valleys. Many mountain peaks are always covered with snow and ice. The altitude at which the eternal snow is first encountered is called the snow line. The mountains form a natural barrier for winds and clouds, so the air goes up and down passing above the mountain peaks. When the airflows rise from the windward slope of a mountain, the low mountain peaks become covered with fog and rain.

The peaks of mountain ridges bathe in the sun, while the valleys and lower mountains lie under clouds. The only clouds surrounding the high peaks are small clusters of ice clouds, while the air is clean and dry.

Notwithstanding the brightly shining sun, its very cold up there, as the sun rays that could warm us are reflected back in the atmosphere by the snow. Around the equator, only the highest mountains, those higher than 5000 meters, are covered by the eternal snow. The nearer one gets to the poles, the lower the snowline gets.

Many meteorological stations are located at the summits of high mountains; they register the atmospheric events as they occur at the high altitude. Its quite tough to work there. The summit of the Mount Washington (NH, USA) is usually covered by a thick fog, the wind speed is often more than 160 km/h, while the temperature may drop below -30 C. Even when the weather is warm, the mountain summits are damp and covered with fog, especially if the damp air flows are around. For example, the mountains on islands in Pacific, like the Tahiti mountains depicted on the photo, are one of the dampest locations on Earth.

Here the winds are very strong and its always cold, even on a sunny day. The wind is always stronger at the summit than in valleys. A partial explanation to this is that the force of the wind rises with the altitude. Another reason is the fact that the wind doesnt pass the mountain on the side but rather over its summit, which also adds to the wind speed.

Blaise Pascal, a famous French scientist, proved the Torricellis discovery of the atmospheres weight in 1648. Pascal postulated that if the atmosphere has weight, then the pressure must be lower at a mountains summit than at its base, as the amount of air above the measurement point is less at the summit and so it weighs less. Pascals guess proved to be correct: the level of mercury in the barometer dropped when the scientist climbed the mountain, signifying that the air pressure also dropped.

MOUNTAINS AND RAIN When a flow of damp air hits mountain ridges, it rises and goes over them. But, during the rise, the temperature of the flow drops, so the water contained in it condenses into clouds. Hence ...