What are the common weather disasters?

Storm is a drastic atmospheric change, which is the inevitable result of improper treatment of surface energy radiation by the atmosphere.

This destructive emotional attack also has its advantages. Scientists estimate that without the heat released by the storm, the temperature in some parts of the earth would rise by 20 degrees Fahrenheit (1 1℃).

In the19th century, meteorologists believed that all storms, including thunderstorms, tornadoes, blizzards and hurricanes, were the main chimneys for hot air to dissipate heat. Below the chimney is the basic low pressure area, which is the key to generating wind. Clouds are concentrated on low-altitude turbulent winds (tornadoes), forming a rising warm air flow. Tornado has become an important part of the surface in the low-pressure area, and it is also a condition for the formation of storms. At the beginning of this century, meteorologists realized that this unified theory of storms could not provide a strong basis for tornadoes to cross the Tropic of Cancer from west to east. Most of these storms occur between 30 and 60 latitudes, which is the main cause of climate formation in North America, Europe and Australia, especially in winter. They include every meteorological change, from gloomy skies to light snow to snowstorms, thunderstorms and tornadoes.

Mid-latitude storms will not form symmetrically like tornadoes or hurricanes on the regression line, as long as warm air is mostly located in the east (or front) of the equatorial direction and the low-pressure center, and cold air is located in the west (or rear) of the polar direction and the low-pressure center. The area where the air masses meet is called the front, which can reach several miles wide and hundreds of miles long. Due to the Coriolis effect, the low pressure center of air mass rotation is sandwiched between the fronts where cold and warm air masses meet.

Meteorologists call the non-occluded peak with warm air instead of cold air a warm front; Non-blocking peak with cold air instead of warm air as exercise mode. This is called a cold front.

Mid-latitude storms can form in many ways. Sometimes, when a low pressure weakened by long-term drift away from the origin slides down the ridge and is pushed back, a storm is formed in latitude. This happens when the low pressure passes through the Rocky Mountains from the west coast.

When gravity pushes a rotating cyclone or mid-latitude tornado from the top of the mountain to Wyoming, the air rotates faster and stretches vertically. Just like a skier clasps his arms, the longer the air is stretched, the faster it rotates. If the air surface has further convergence in the horizontal direction, the intensity of mid-latitude tornadoes will be stronger. This low-level climate instability will also lead to the formation of polar fronts.

polar face

Polar front is two permanent areas (one in the northern hemisphere and the other in the southern hemisphere), which are formed by the collision of equatorial air mass and polar air mass when they rotate around the earth. When the mid-latitude depression meets the polar front, a strong storm will occur due to the reaction between the low-pressure storm and the upper air circulation surface.

It is difficult to determine the causal relationship between low pressure and the air above it. Many things happen almost at the same time. On the cross section, the layout of cold and warm air masses makes the cold wave of the fast-flowing polar jet grow rapidly, usually parallel to the polar front. The wave-like ups and downs of rapids are horizontal, and they are also vertical. Meteorologists call it low-pressure trough and high-pressure ridge. Although the number of cold waves can vary, it is generally three to five big cold waves, which is called the Rosby cold wave.

Because polar jets take a wavy path, they sometimes accelerate; So far away from the thin polar regions. This acceleration, or jet, will weaken the ground pressure below by reducing the weight of the air above, and the ground air will rise immediately to fill this gap, and the combined wind will bring the cold and warm air masses together, further strengthening the surrounding ground low pressure.

Convergent wind on the ground brings a large number of cold air masses to resist the rise of warm air masses and further increases the jet stream in the upper air by strengthening their low pressure troughs and high pressure ridges, which further strengthens the jet stream and causes more ground convergence.

This feedback increases the instability of cold and warm fronts's atmosphere. In order to release energy, the hot air mass climbs above the cold air mass, and the rising air mass produces clouds-smooth clouds sometimes climb slowly along the warm front, sometimes parallel to violent thunderstorms, and sometimes go hand in hand with the cold front. The resulting front slope and bad weather will be aggravated with the change of relative temperature. Finally, the cold front began to rotate around the low-pressure area like the door rotating around the door axis, and the area of warm air kept shrinking, while the wet air was sandwiched between cold and warm fronts. Finally, the cold front catches up with the warm front, and the door closes. This process is called "occlusion". Blockage means that the cold air mass is squeezed into the warm front, or obliquely cut on the warm front. Either way, the initial heating mass area will end at the upper part. It flooded the center of the storm. This center used to be a storm with a cold air mass, but now it is a warm air mass with spiral motion, wrapped in a cold air outer layer. Compared with the original feedback chart, the temperature has been lost, and the imprisoned storm has also lost its energy, gradually weakening until it disappears completely.

tornado

At a temperature of 54,000 degrees Fahrenheit (about 30,000 degrees Celsius), lightning is the hottest thing on earth. The broad beam energy of its current is six times that of the surface of the sun. It can burn a hole in most metals, or smash a strong trunk into thousands of pieces. This heat energy can even melt the underground sand and form a special rock called lightning lava. Norwegians also believe that this kind of stone shows that lightning is Thor's harpoon.

However, the burning of lightning is actually the result of the collision of the upper tropospheric ice when the temperature is lower than 0 F (-18 C). This repeated collision is the product of heat release from the earth's surface after being irradiated by the sun. Hot and cold, before and after, and thunderstorms are the results of temperature differences in different parts of the troposphere.

At an altitude of nearly 65,438+05 miles (24 kilometers), the temperature difference between the troposphere is about 65,438+050 F (83℃). On average, thunderstorms release several times as much energy as Hiroshima's atomic bombing. Storms, and sometimes even tornadoes and hailstones, suddenly strike the earth's surface with lightning.

squall line

Thunderstorms can also connect squall lines or fronts together, making them last longer than the original cloud bubbles. The violent front driven by downward flow will produce a powerful process, providing a new updraft for a group of storms. If squall lines and other thunderstorms can effectively store warm water vapor high in the atmosphere, they can last all night. In fact, meteorologists have recently discovered this kind of storm group that can last for several days, and their cloud interfaces sometimes spread to Kansas, covering an area equivalent to hundreds of independent thunderstorms.

Thunderstorm combination can also cause strong direct wind, which is called "Derlique wind". 1993, Derek crossed Nebraska and half of Iowa in just 12 hours at a speed of 70 miles per hour (1 12 kilometers).

The deadliest storm caused by downward flow is actually the smallest. When the descending airflow is cooled by the intense evaporation rainfall, it can accelerate its movement and attack the ground like a bomb. In less than two miles (three kilometers), a powerful storm can become very dangerous. 1989, just five minutes after President Reagan's helicopter landed at Andrew Air Force Base, the storm swept through, and the storm galloped on the ground at a speed exceeding 100 miles per hour. In recent years, it is said that other micro-storms have caused hundreds of flight accidents, and the ground losses caused by them are sometimes close to fixed hurricanes.

flood

A rainstorm can trigger a flood, and the sudden flood will be fatal. In the United States alone, 100 people die from floods every year. They will happen in an instant. Usually, they are caused by heavy rain, such as 1989, which washed away the foundation of the Johntown dam in Pennsylvania. A stream of water higher than two stories rushed to the town faster than a locomotive. Took 2,200 lives. 1976, the Thompson Grand Canyon was flooded, and the storm was contained by a weak air mass moving westward against it. It usually rains in the northeast when a thunderstorm travels; But the rainstorm is located above the canyon, and all the rainwater is concentrated in one place.

Usually, these extreme rainfalls are caused by a series of thunderstorms. 1977 in Kansas city, two different rainstorms occurred in the same suburb within a few hours. Heavy rain caused the river to flood, damaged houses and killed 23 people.

Due to the topographical structure, the flood will worsen. As far as the flood in Thompson Grand Canyon is concerned, the nearby rocky cliffs made the water flow into the river below people. If it is a gentle slope with more soil and thicker vegetation, most of the water will be absorbed. Urban canyons have also aggravated floods. The paved road greatly increased the rainwater flow by 500%. 1966, after the rainstorm, the Arno River in Italy overflowed its banks. For weeks, the stone streets of Florence have looked more like Venice's waterways.

However, not a drop of rain can cause a flood. 1977 In early April, a snowstorm with a thickness of 17 feet (43 cm) greatly exceeded the capacity of rivers in North Dakota. The snowfall in one season exceeds 100 feet (254 cm), which melts in a few weeks and overflows the banks of the Grand Fox River. 910 of the city was flooded, and about 1000 buildings and households were destroyed. In Canada and northern New England, river ice flows down the river in spring until it is blocked. The water flowed backwards and gradually overflowed under the ice. Then the ice dam collapsed, causing water to flow into the community and causing floods. However, the continuous rain for several days triggered a large-scale flood. When the Yellow River in China flooded and changed its direction in 1887, almost1100,000 people died. During the period of 1993, the flood of Mississippi-Missouri River was caused by the snowstorm in spring and summer, because the rainstorm was continuous. In terms of width, the river rose more than 7 miles (1 1 km), and the flood covered nearly half of Indiana. Unfortunately, when the jet stream hovers around the high-pressure air mass in the same area, the rain will fall to other places. This happened in 1988, which led to a drought, and its disaster was no less than that of 1993, which lost 20 billion yuan. 40 days and nights in any weather, whether wet or dry, is indeed equivalent to the scale of the disaster mentioned in the Bible.

Tornadoes, tornadoes and sandstorms

There may not be a weather phenomenon that looks as terrible as seeing a slender twisted funnel detour to the ground. Although the tornado is small in scale and short in life, it causes more damage in an instant than any other weather activity on earth.

On the earth, the plains are more prone to tornadoes than other places. About half of the nearly 1000 tornadoes in the world every year occur in the United States. However, other parts of the world have also experienced tornadoes. Eastern India and Bangladesh, the Himalayas near the Indian Ocean, are particularly prone to violent tornadoes. In fact, the deadliest tornado in the world was 1989 near Dhaka, Bangladesh on April 26th, causing 1300 deaths. It is reported that tornadoes occur every year in Europe, Russian Federation, the eastern plains of China and the eastern and western fringe areas of Australia.

Seen from the surface of the earth, the most vicious tornado swept across the ground with a wind speed of 250 miles (402 kilometers) per hour. Violent tornadoes can be more than 1 mile in width and travel at a speed of 40-60 miles (64-96 kilometers) per hour for more than an hour. However, most tornadoes do not have these characteristics, and their winds are much weaker. A typical tornado is only 100 ~ 200 feet (30 ~ 60 meters)-less than the distance between city streets, and can travel for several minutes at the speed of 20 ~ 30 miles (32 ~ 48 kilometers) per hour. The average length of tornadoes is about 9 miles (14 km), but some can travel hundreds of miles and then disappear. Even if the tornado is relatively weak, the capricious "funnel" will also produce fear, which can be as gray as ghosts and as dark as night. It's like a pencil, a cigar, an ice cream cone, or a turbulent dark cloud. Older people try to describe its sound: 1 10,000 wild bees, a jet engine, a large group of tanks moving forward.