The mountain peaks are often snow-covered due to the higher altitude, which leads to a decrease in temperature. The cold air holds less moisture, which promotes the formation of snow. In addition, the upward winds transport moisture and promote condensation and the formation of precipitation in the form of snow.
When you climb to higher altitudes, atmospheric pressure decreases: there is less air and its molecules expand more. This expansion leads to a drop in temperature, which is called adiabatic cooling. Basically, for every 100 meters you gain in altitude, you lose about 0.6 to 1 degree Celsius in temperature. So the higher you go, the cooler it gets, even in the middle of summer. Beyond a certain altitude, the temperature drops low enough to maintain snow year-round, creating what are called eternal snows. That's why the peaks of mountains, even in the tropics, often remain white with snow.
Warm, humid air rises toward the peaks. As altitude increases, the air cools, and the water vapor it contains begins to condense to form clouds. If these clouds reach negative temperatures, the tiny droplets suspended within freeze into tiny ice crystals. These crystals gradually grow larger until they become heavy enough to fall back to the ground: it then starts to snow. The higher and colder the terrain, the more frequent this phenomenon is, allowing for regular and abundant precipitation in the form of fresh snow on the summits.
Winds and atmospheric currents play a major role in how snow accumulates on peaks. When a mass of moist air from the oceans encounters a mountain, it is forced to rise. As it ascends, the air cools, and the moisture it carries condenses into clouds, then falls as snow, especially if it's already cold up there. This phenomenon is further amplified by certain dominant winds that constantly push the moist air against a specific side of the mountain. As a result, that side often has more snow than the other side, which is sheltered from the wind and is drier. Certain atmospheric currents, such as jet streams, also indirectly influence where and how snow will fall by steering storms and cloud masses toward specific mountain ranges. They often determine the final distribution of snow cover.
Mountain reliefs play a major role in promoting snow cover. When a mountain range blocks the passage of clouds, they are forced to rise along its slopes. During this ascent, the air rises and cools: this is known as the barrier effect. As a result, moisture condenses, and precipitation, often in the form of snow at high altitudes, significantly increases. In addition, the reliefs sometimes feature sheltered hollows or valleys where snow can accumulate for long periods, creating particularly snowy areas even long after a snowfall. One more interesting thing, certain mountainous shapes promote accumulation through phenomena like cornices or drifts: under the influence of the wind, snow piles up and clings to ridges or in strategic locations, reinforcing the impression of continuous snow cover.
Climate change is gradually reducing the snowfall on many mountain peaks around the world, affecting biodiversity, water resources, and local economies that depend on tourism and winter sports.
Some mountains, like Mount Fuji in Japan, are active or dormant volcanoes covered with snow at their summit, a surprising proof that snow and volcanic activity can coexist!
The inhabitants of the Himalayas have been using the technique of storing snow and ice from the mountains in winter to have fresh water in summer for centuries. These artificial ice reserves are called 'Ice Stupas.'
The Mount Everest is so high (8,848 meters) that the temperature at the summit hardly ever exceeds -20°C, even in summer!
Climate change is leading to an overall increase in average temperatures, resulting in reduced periods and volumes of snowfall in the mountains. This is manifested by the retreat of glaciers and a significant decrease in the snow-covered areas of the peaks in various mountain ranges around the world.
Although we get slightly closer to the sun at higher altitudes, this proximity is minimal compared to the Earth-Sun distance. The decrease in temperatures is mainly due to the reduction in atmospheric pressure and the scarcity of molecules capable of absorbing and retaining the sun's heat. Thus, the higher we go, the colder the air becomes.
The permanent snow line strongly depends on latitude, orientation, and local climate. In the tropics, this permanent snow line can exceed 5000 meters, while in temperate regions, it can range between 2500 and 3000 meters, and reach around 1000 meters only in polar regions.
No. Only the peaks of mountains that are sufficiently high or located in cool or temperate regions experience lasting or permanent snow cover. Mountains situated in tropical regions or at too low altitudes may not meet the necessary conditions for persistent snowfall.
Even during the summer months, temperatures at the summit of mountains often remain below zero degrees Celsius due to the high altitude. This greatly limits the melting of the snow accumulated during the winter months. Furthermore, the increased reflection of solar rays by the snow itself, known as albedo, exacerbates this phenomenon by further limiting warming.
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