Why can't the fire in America go out?

Why can't the United States put out the California fire?

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The biggest mountain fire broke out in southern California, USA, and the flametongue striker aimed at Los Angeles. Not only farmland and villagers in suburban counties of southern California are affected, but also celebrities and wealthy businessmen who buy houses and land around Los Angeles. This is not the first mountain fire that California has experienced. Why can't the United States put out the California fire? Please read today's article.

The dry autumn and winter seasons in California have always been the high incidence of mountain fires. However, it is not a simple matter that the authorities must issue the highest level of purple warning (unprecedented in history) when such a high-level fierce mountain fire occurs.

Why do mountain fires happen every year, but they are particularly fierce this year? This will take you to see the reasons behind the terrible mountain fires in California.

Wind helps fire, and fire borrows wind.

California is a maverick existence in American territory.

On the surface, this state seems to be a continental plate on the North American continent, but its geographical position can be compared with Fujian or Guangdong in China-it has a clear border with the mainstream world in the central and eastern United States due to the barrier of surrounding geographical conditions.

Three west coast States that are relatively isolated from the central and eastern parts of the United States

On the northern edge of California, there are dense forests and hills at the junction with Oregon; On the east is the dense Sierra Nevada, which is separated from Nevada; In the southeast is the Mojave Desert, which is separated from Arizona. Even if its state boundaries are drawn by artificial straight lines, it is reasonable that this state is framed as coincidence by a large number of natural landforms.

However, under this natural geographical condition, there are also hidden dangerous seeds of mountain fires.

The natural terrain of California

The segmentation is very obvious

And synchronized with the artificially drawn state boundaries.

Crossing the eastern part of the Sierra Nevada and entering the territory of Nevada is the famous terrain great basin in the western United States. This basin has bred a large number of biological species unique to North America, and also preserved some settlements of Indian tribes. The average elevation difference between the basin and the Sierra Nevada is above 1000 meters, which provides the possibility for the change of airflow.

The Sierra Nevada is a barrier to airflow.

Because the temperature of sunlight absorbed by the basin rises rapidly during the day, the air gathered in the basin will rise to the vicinity of mountains due to heating, resulting in higher air density at the same altitude above the basin. Under the pressure difference, the air then moves to the low pressure area on the west coast.

Because when the airflow blows to the coastal areas, it will pass through some ravines and be squeezed to increase the speed. The maximum wind speed of this wind can reach 60km/h, which is helpful for the rapid spread of the fire. According to the local fire department, it only takes one minute for the wildfire to reach the size of the football field, and there is no time to arrange fire prevention facilities at all.

The wind from Nevada

Increase the firepower, from west to south.

To make matters worse, this airflow will cross the Mojave desert on its way south. The composition of the air over the desert can be imagined. When the wind temperature rises and the relative humidity drops, it soon becomes extremely dry air. When it arrived near Los Angeles, the airflow had turned into a dry and violent gale, which was called "Santa Ana" in the news report.

Compared with northern California

The isolation of southern California from neighboring deserts

It is undoubtedly a very unfavorable factor.

Los Angeles in the fire

There is also wind in northern California, the cause of which is almost the same as Santa Ana wind, but the direction and composition are not the same.

This is called "Devil Wind" (Diablo= Big Pineapple? ), on the way to the Bay Area of Northern California, it won't pass through the desert terrain, but it will cross the mountains twice-the first time from great basin to the central valley, and the second time from the valley to the Bay Area.

These two mountain climbing processes will have some thermodynamic effects on the air (see the meteorological term foehn), which will increase the temperature and decrease the humidity, and the effect is similar to crossing the desert.

Big pineapple and Santa ana ...

Feeling like a couple?

These two air currents are important factors to promote the continuous mountain fires in California every year. The so-called wind helps fire, and fire borrows wind, which complement each other and eventually lead to great disaster.

But if it weren't for some coincidences, this year's fire wouldn't have burned so badly.

Wet first and then dry, natural fuel

In California, where the Mediterranean climate prevails, winter is the main rainy season, but the precipitation rarely exceeds 7 inches (180mm). Last winter, California experienced a rare wet winter, and the average precipitation in January reached a rare 9.74 inches (250 mm), which nourished everything in California's winter.

The precipitation in January this year

It's really amazing

High rainfall revived the dormant plants in the local forest, and they grew wildly, so that many green areas never existed in previous years appeared. At first, people thought it was a good thing, and Californians were still commenting on the new vegetation.

However, the good times did not last long. After the ultra-high precipitation winter passed, California ushered in a rare dry summer in history. In June, July and August, the rainfall in California was lower than the average level in previous years, and the temperature was much higher than in previous years.

The sudden drought suddenly killed the plants that grew freely in winter and turned these lush vegetation into dead branches and leaves. Too dry summer evaporates the water in leaves, making them the best fuel. A single spark can start a prairie fire.

Observe the distribution of plants around Ventura county, and you can see the clue. From 1 month to March, the main color here is green, indicating that the vegetation is well covered and all are alive.

Something has been wrong since April, and yellow areas began to appear in the valley with higher temperature, indicating that the plants are dying. After a whole summer, this area in the north of Ventura County has turned into a fuel pile, waiting for a Martian to appear.

Changes of vegetation in Ventura county

Northern California is not much better. In the vigorous mountain fire in June+10, 5438, the same thing happened around santa rosa surrounded by wildfires, just like around Ventura.

After a period of drought, the lush forests in winter and spring turned yellow. It is these natural fuels that caused several wildfires in October.

The area around santa rosa is yellow. . .

In fact, Americans have long recognized the role of dead vegetation in forests in fueling wildfires.

In the early days of dealing with California mountain fires, the attitude adopted by Americans was to kill all possible signs and put out all small mountain fires in time. The code of conduct that seems to conform to the concept of fire prevention has not achieved enough results.

Because there have been no large-scale mountain fires for many years, dead leaves and branches have accumulated in the forests of California. Once a fire breaks out, it will wreak havoc and there is no way to put it out.

fire ...

So from 1970s to 1980s, American fire departments and forestry departments began to consciously look for areas where too many dead plants had accumulated in the mountains, and eliminated these potential safety hazards by artificial ignition, so as to reduce the intensity of natural wildfires from the source.

This control method is still controversial, but it does have some effects.

Only this year, the climate in California experienced two days of fire and water in a few months, and the newly added vegetation quickly became dead branches, making it impossible to make a fire artificially. The California Fire Department can only say that it is beyond the reach of God who likes pranks.

But if it were not for some human factors, the loss caused by this fire would not be so great. Some human factors and natural conditions make the Southern California fire so terrible.

Man-made disasters have caused great losses.

In English, mountain fire is also called wildfire, which sounds natural and wild. However, this is not the case. The source of a large number of wildfires comes from artificial ignition.

According to statistics, 90% of wildfires in the United States come from human activities such as cigarette butts discarded by climbers and unlit bonfires in campsites. It is said to be a wildfire, but it is actually related to people.

Remember to put out the bonfire next time.

Although the cause of this mountain fire could not be confirmed before it was put out, human activities are likely to be the cause of many fires in southern California. These arsonists may not be intentional, but the final result is the property loss of the people in the whole state, which shows the importance of entering the forest area to protect forests and prohibit fires.

In the process of fire spreading, it is also a typical man-made disaster to cause such great property losses.

In recent years, California's economy has been very strong in the American economic map. Originally, it was the best agricultural production area in the western United States. After the emergence of important port cities such as the San Francisco Bay Area and Long Beach Port in Los Angeles, it attracted a large number of Americans to come here for gold.

The process of modernization has brought a prosperous entertainment industry (Hollywood) and high-tech industry (Silicon Valley) to California. Coupled with the pleasant Mediterranean climate and coastal scenery, the population of California is expanding.

California shines on the west coast

The expansion of population has brought about the expansion of cities, which is a beautiful sight that many cities in China can't wait for, but it has also brought huge problems. The scientific planning speed of the city is far behind the rapid expansion of the city, and a large number of residential areas have entered the forest areas on the edge of the city.

According to a statistic by the Federal Emergency Management Agency at the beginning of this century, 38% of new houses in California were built in this area. Among these houses, there are many famous people's mansions.

Tens of millions of California luxury homes.

Half of Silicon Valley.

This newly expanded urban area is called "wasteland-urban interface area", or WUIs for short, which has become a common practice in California.

Radloff, a professor at the University of Wisconsin-Madison, said that such areas are "medieval cities backed by big forests" and lack modern urban management and self-protection capabilities.

Don't play with fire in the back hill.

If we observe the relationship between WUIs area and many wildfires that broke out in northern and southern California this year, we can find that wildfires are mainly distributed on the edge of such areas.

Because the residential areas here are dense and close to the birthplace of wildfire, it is easy to turn into a sea of fire, and the resulting economic losses are incalculable.

The blue area is the WUIs area.

The red dot is the source of this year's large and small mountain fires.

Fire and water are ruthless, and everyone knows that disasters should be avoided, but when disasters do occur, human efforts are so insignificant.

Preparations for natural disasters, coupled with man-made disasters, have made California's mountain fires continue this year, causing heavy losses. Although people here have long been accustomed to the arrival of mountain fires, who can not help but feel distressed when they watch the flames devour their homes and property?

No one can predict the future, and no one is immune from the evil forces of nature. Perhaps what we can do is to take preventive measures to protect ourselves from being swallowed up by disasters in sudden danger.

reference data

/projects/la-me-California-fire-seasons/

/News/Local/Southern California-Wildfire -205975 17 1.html

https://en.wikipedia.org/wiki/Diablo_wind

https://en.wikipedia.org/wiki/Santa_Ana_winds

Published on 20 18-07-27? The copyright belongs to the author.