Is a mountain-specific weather phenomena. Why do mountains occur foehn? This is because the air flow over mountains, appeared descending movement of. From the meteorological perspective, any group that rose to a height of air from the ground, each 1,000 meters higher, the temperature dropped an average of 6.5 ℃; the contrary, when a mass of sinking air from the upper to the ground, each 1000 meters down, the temperature The average increase of about 6.5 ℃. That is, when the air from the altitude of 4000-5000 m high mountains down to the ground, the temperature will rise above 20 ℃, cool climate will heat up immediately. This is have a This style does not appear as often Xiangshan wind, it is pressure in the mountains on both sides occurred under different conditions.
in the mountains on one side of a high pressure, the other side is low pressure, air from high pressure areas to low pressure area moving. In the case of air moving mountains blocked his way, forced to rise, pressure drop, air expansion, the temperature also decreases. Every 100 meters increase in air temperature fell by 0.6 ° C, when the air rises to a certain height, water vapor condenses when cooled, the formation of rain and snow fall. Air reaches the ridge in the vicinity, to become thin and dry and then climbed over the ridge, downslope drop down the air in the process, become close again, and the emergence of the phenomenon of warming. L00 meters of air per drop, temperatures will rise 1 ° C. Therefore, the air along the tall mountains into the foothills of the settlement, when temperatures often have a sharp increase. Windward and leeward sides of the air, even if the height,Discount UGG boots, the leeward side of the air temperature is always higher than the windward side. Whenever the leeward slopes of blowing hot, dry foehn, the windward slopes often rain or snowfall.
2, foehn foehn effect
the harmful effects of many. It is often so dry fruit and crops, reducing yield, forest and villages of the fire spreading and causing damage. Foehn in the Alps scrape days, daytime temperatures rise above 20 ℃ can be sudden, early spring as the weather becomes like summer, not only hot, but very dry, often fire. Burning up a strong wind, can scorch the leaves of trees, land cracking, resulting in severe drought. Foehn in the alpine region can be a lot of snow, causing flooding upstream valley; sometimes can cause an avalanche. If the terrain suitable, strong foehn can cause local storms, scrape away mountain farmhouse roofs, uprooted crops, uprooted trees, damage forests, lakes and even the boats on the water accident.
foehn and disadvantages, but it is also beneficial. As it can accelerate the melting of snow in winter, do not wait until next spring, cattle and sheep grazing in the open a can. North America, Rocky Mountain, deep snow in winter, spring burning winds, not long before all the snow will melt, the earth covered with lush grass, providing pasture for the livestock, which the locals call it, . Foehn also enriched the local energy resources, like the upper Rhone valley of Switzerland corn and grapes, that is, by the foehn heat and mature; the foehn not affect neighboring areas, these crops would be difficult to mature. Another example: the foehn to a lesser extent, to increased local heat, corn and fruit trees can mature early, so the former Soviet Caucasus and the residents of Tashkent oasis, simply call it
Hot wind in early summer, some areas of China often give rise to a high temperature, low humidity of the air, which is dry heat wind, also called It is a short duration (typically 3 days) of a particular weather phenomenon.
as the natural characteristics of different parts, hot wind causes are different. Each year in early summer, hot weather inland areas of China, scarce rainfall, strong temperature, air pressure decreases rapidly to form a force strong continental heat low. Around in the hot low pressure, pressure gradient increased with increasing air mass temperature, so dry and hot air flow around the heat on low spin, forming a hot, dry wind, hot wind that is. Strong hot wind, the local wheat, cotton, fruits can cause harm.
dry climate of Mongolia and China, west of the Loop and Xinjiang, Gansu area,Discount UGG boots, is often low pressure area generated mainland fever. After the heat source of low pressure left along the way through the dry heat of the Gobi desert, will become more dry and hot, dry hot wind has also become more powerful. Tarim Basin in the center of Eurasia, climate extreme drought, a strong cold front crossed the Tianshan Mountains, the Pamirs generated from the
in the Huang-Huai plain, dry hot wind is the main reason for the formation of the region's air dry basis. Spring and early summer, is the largest angle of the Northern Hemisphere season of direct sunlight, but it is also the rainy season in northern China before the arrival of sunny, dry period. Under the control of the dry air mass, where fine, dry, windy,UGG boots cheap, the ground temperature fast (average maximum temperature of up to 25-30 ° C), chance of rain caused by condensate clouds less easy to form the dry hot wind. This dry heat wind, this area of wheat growth and development of late adverse.
in the Yangtze River Valley, Dry hot wind in the southwest of the western Pacific subtropical high air flow under the influence. Pacific subtropical high is a deep, warm low pressure system from the ground to the upper formed by warm air. Spring and summer, this high pressure to stay over in the Yangtze River Valley, then gradually moving north. As the high pressure area, the wind is blowing clockwise direction, so the subtropical high in the west, southwest wind blew. In the subtropical high in the north and west by southwest wind of this unit to produce hot wind weather. Early summer, continue south to the north is still cold high pressure, weakened and degeneration; when it merged with the subtropical high, the force has been strengthened to continue in fine weather, hot wind is even more evident.
in the Yangtze River Basin, the rainy weather after the dry hot wind southerly often accompanied by
hot wind on crop damage, mainly due to high temperature, drought, strong winds forced the air and increase soil evaporation, crop water consumption of the body quickly, thus undermining the chlorophyll pigment, hindered crop photosynthesis and the synthesis process, the plants soon dried green from the bottom up. Especially the hot wind, often with damage crops and drought. Root crops should not have been on the absorption of water, and dry heat wind, but from the stems and leaves to go grab a lot of water, making crops wither faster chlorosis.
hot wind often occurs in the early summer, is filling period of wheat in northern China face the dry heat wind, ears of corn will be roasted not filling ahead of time, cause serious cuts.
harmful levels of hot wind, hot wind occur a few days ago with the weather condition. After the rain suddenly sunny, high temperature and low humidity followed, hot weather, heavy damage. In the hot wind slightly before the occurrence of such precipitation, the dry hot wind damage mitigation is beneficial. Sowing time, sooner or later from the point of view, late wheat vulnerable. Therefore, farming proverb said: View from the farming season, Grain Budding is closed, the farming proverb of In other words, wheat Xiaoman If we can not filling milk, hot wind is vulnerable to hazards. Cyclones Cyclones are playing round the
air vortex, mix the dust from the ground flying into the air vortex, this vortex is what we usually see the cyclone, which is caused by air flow a natural phenomenon, but why fight the wind walk around it?
We know that when the air around the ground, like trees, hills, buildings and other places where uneven flow, or air and ground friction, it is necessary rapidly change its direction, so may have to move together with the air vortex, which whipped up a whirlwind. However, this whirlwind few, very small.
cyclone formation of the main reason is that when a place was very hot when the sun tan, where the air will be inflated, some air was packed up to the high altitude then decreased gradually after the temperature began to to the surrounding flow, and finally sank to the ground nearby. At this time, the regional air reduces heat, pressure was reduced, while the surrounding temperature is lower, the air density is high, with heating of this part of the air from the air, came down, so the air increased, pressure increased significantly. Thus, high pressure air to take in surrounding areas, where the center of low pressure stream, with the same water flows. However, because the air flow in the earth, the earth is always moving from west to east rotation, then the air flow during rotation of the Earth would be gradually to the right side to (the original north wind deflection into the Northeast wind, south wind deflection into the southwest wind, westerly deflected into the northwest wind, wind deflection into the southeast wind). So the more cold air from blowing around, on around the low pressure area rotating heat up and become a clockwise rotation in the opposite direction and watch the air vortex, which formed a whirlwind.
the center of this whirlwind, as warm air rising, coupled with continued rotation of air around, so it is easy to dust on the ground, leaves, paper and other paper into the air, and with the air flow rotating fly. If the cyclone is strong, and sometimes will ground some of the small animals such as snakes, insects, etc. into the air to the volume, in the diffuse dust in the wind to.
generally small cyclone height is not too large, as it were on the ground friction or houses, trees, etc. when blocked, it gradually dissipated into a normal wind.
Perhaps someone will ask: if the ground is easy from the whirlwind heat, that summer than the spring is hot, why the summer and spring cyclone cyclone little more? This is because although the hot summer weather, but the ground vegetation green, wet land, the temperature difference is low, they rarely blow whirlwind summer. However, in the spring, the leaves have not full out, the grass has just germination, crop land is a bare, no cover did not block everything, which is easy drying heat, so that the air temperature changes on the ground more, it is easy to scrape Cyclones .
cyclone to mix the dust and chaos of paper fluttering in the air, of course, able to ground the heat and moisture into the air, therefore, causing air heat, water vapor and other vertical mixing, so that the air such as heat and water vapor vertical distribution. However, in the ground near the cyclone is very small, little effect of vertical exchange, so close to land surface layer, formed a special microclimate tornado
tornado, because the ancient mythology, sprang from the waves, clouds in the East China Sea wrestle very much like the dragon is named after, it also has many aliases, such as Now we know that a tornado is a violently rotating column of air with a round, it's connecting the top and the thunder clouds, the bottom and some hanging in the air, some directly extended to the ground or water, while rotating, while moving forward. Occurred in the sea, like From afar, it is not only hanging in the air and threw it like a python,UGG boots clearanc, and kept swinging it like a elephant nose.
this big In thunder clouds, the air turbulence is very powerful, upper and lower temperature gap. On the ground, the temperature is 20 Celsius, several times, more to the high altitude, the lower the temperature. Cumulonimbus at the top of more than 8000 meters in altitude, the temperature as low as minus 30 Celsius, several times. This cold air above the rapid decline in the air following fierce heat up. Updraft to reach high altitude, if the experience level of large wind direction, will force the rising air currents As the turn of the upper air disturbance, resulting in rotation effect, the formation of many small vortex. These small vortices gradually expanding. Agitate up and down more and more intense, and finally form a large vortex. First, a large vortex rotating around the horizontal axis, the horizontal direction was the formation of a rotating column of air. Then, the rotating column of air gradually curved at both ends, and from the cloud base slowly drooped. Cumulonimbus is on the way forward, left out from the cloud body is called Out into the ground is usually the right tornadoes, tornado left few opportunities to stretch down.
Also, tornadoes are also more likely the intersection of two squall lines occurred. Squall line often strong cold air in the hot season, the most
tornadoes often more than one. Sometimes from the same piece of cumulonimbus can be two, or two or more of the Only some of the
the scope of a tornado is small, the average diameter of 200-300 m; diameter of the smallest, but tens of meters, only a very small number of large diameter, to reach over 1,000 meters. Its life expectancy is short, often only a few minutes to tens of minutes, no more than a few hours. The average speed 15 meters per second, the fastest up to 70 meters; moving mostly in the length of the path about 10 km short of a few dozen meters, up to several hundred kilometers long. The width of its damage on the ground, generally only l-2 .
tornado extremely violent temper. Everywhere in it, roar like thunder, and strong aircraft fleet in the lower atmosphere as if passing. This may be due in some part of the vortex of wind speed over speed of sound, and thus the shock waves of small amplitude. The wind speed inside a tornado, exactly how? It is also not determined, because any anemometer are unable to withstand the destruction of it. In general, the wind speed may be 50-150 meters per second, extreme cases, even up to 300 meters per second, or more than speed of sound.
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