Process and principle of foehn effect

According to meteorologists, wind burning is a unique weather phenomenon in mountainous areas. It was caused by the sinking of the airflow after crossing the mountain. When a mass of air sinks from the sky to the ground, the temperature rises by an average of 6.5 degrees Celsius for every drop of 1000 meters. That is to say, when the air falls to the ground from a mountain with an altitude of 4000 meters to 5000 meters, the temperature will rise by more than 20 degrees Celsius, making the cool climate suddenly hot, which is the reason for "burning wind". For example, the foehn in Taitung, Taiwan, was formed when the southwest airflow crossed the central mountain range, and the water vapor was blocked and evaporated, forming a dry and hot foehn.

When the airflow is perpendicular to the hillside or the included angle is large, the wet airflow will pass through the hillside, which will have different effects on the temperature and precipitation of windward slope and leeward slope.

Burning wind can promote the melting of Chun Xue and the early maturity of crops; At the same time, it is also easy to cause natural disasters such as forest fires and droughts. [2]

The damage caused

When the foehn is strong, the temperature rises rapidly and the air humidity decreases, which can wither crops, scorch leaves, crack the land and even cause forest fires, droughts and other disasters. In mountainous areas, it can also melt a lot of snow and cause floods; Sometimes even people will find it difficult to breathe and their bodies will suddenly weaken.

Burning wind has many hazards. It often dries up fruit trees and crops, reduces production, spreads fires in forests and villages and causes losses. /kloc-in the 0/9th century, there were several famous big fires on the northern slope of the Alps, all of which occurred during the prevailing period of foehn. Foehn can melt a lot of snow in mountain areas and cause floods in the upper reaches of the valley; Sometimes it can lead to avalanches. If the terrain is suitable, strong wind burning can cause local wind disasters, blow away the roofs of rural houses in mountainous areas, blow down crops, uproot trees, endanger forests, and even cause ship accidents on the lake.

165438+1October 14 night, foehn wind formed a strong storm in some parts of Austria, attacking all farmland and villages at the speed of 160 km per hour. Where the burning storm passed, the roofs of hundreds of houses were blown away or crushed by the wind, many trees were uprooted or broken, power supply and telephone communication were interrupted, and road and railway traffic was blocked. Two people died and millions of euros were lost.

On May 1 1, 2004, there was a foehn in Taidong, Taiwan Province Province, and the high temperature of 40.2 degrees Celsius set a century-old record in Taidong. At noon that day 12: 57, a strong burning wind suddenly blew in the downtown area of Taitung, and the indoor and outdoor temperatures rose rapidly like an oven. At 13: 00 and 14: 00, the temperature soared to 40.2 degrees Celsius, making the local residents miserable. Some people turned on the air conditioner and hid in the house. Some people took their children to the clear stream in the suburbs to enjoy the cool. Farmers are even more bitter, because they are most afraid that hot leaves and tea trees will wither slowly in the strong burning wind.

In high mountain areas, burning wind can also lead to melting snow, flooding upstream valleys and sometimes causing avalanches.

In addition, when windy weather occurs, many people will have uncomfortable symptoms, such as fatigue, depression, headache, bad temper, palpitation and edema. Medical meteorologists believe that this is caused by the dry heat characteristics of foehn and the influence of changes in atmospheric electrical characteristics on human body. [2]

profit

Burning wind can sometimes bring benefits. In the Rocky Mountains of North America, the snow is deep in winter. When the wind blows in spring, the snow melts quickly. Snow water makes the land full of lush grass and provides pasture for livestock, so the locals call burning wind "snow eater" Lighter burning wind can increase local heat and make corn and fruit trees mature ahead of time. For example, residents of the Caucasus and Tashkent Oasis in the former Soviet Union called the burning wind "corn wind".

Use and prevention of editing

On the windward slope of the mountain, the water mass cools with the elevation of the terrain, forming precipitation. Therefore, planting trees and grass on windward slopes can prevent soil erosion, and the existence of forests can increase precipitation opportunities due to their humidification and cooling effects; Build reservoirs and dams at appropriate locations, and send the stored water to water-demanding areas through water pipelines to adjust the uneven distribution of precipitation in time and space.

People should be careful of the dry and hot wind generated by going down the leeward slope of the mountain to prevent the occurrence of fire. Construction units should pay attention to dust prevention, and residents should drink more water and eat more vegetables and fruits to avoid diseases such as upper respiratory tract infection. Afforestation in dry-hot valley can be expensive, but it is of little significance to popularize it, and it is even more impossible to last, because the existence of leeward slope forest is very difficult, which has been proved in dry-hot valley in southwest China.