The weather is unusually hot this year. Are you aware of global warming?
Asia, North America and other places have experienced historical heat waves. In Europe, the Iberian Peninsula suffered the highest intensity of high temperature attack in history in July, and Andalusia in southern Spain was autonomous.
In some places, the highest temperature during the day even reached 45 degrees Celsius. According to incomplete statistics, the number of deaths caused by high temperature in Spain.
An increase of 2 124 people over the previous year. The temperature in Losa, a city in central Portugal, reached a record 47.3℃. And France in central Europe
It is the driest on record, and the national rainfall is only 15% of previous years.
Located in temperate maritime climate.
The highest temperature in some parts of Britain reached 39℃, which made it declare a national emergency. At the same time, the British Meteorological Office released extremely high temperatures.
Warm red warning.
In the Middle East, there is an extreme high temperature of 47.2℃ in southeastern Turkey, and the highest temperature in the world this year is 53℃ in Iran.
Warm. In the Russian Far East, high temperature caused many mountain fires in Siberia, and the fighting is still going on.
In North America and Greenland, the ice sheet has melted so much that researchers can even wear short sleeves for exercise. In the United States, Texas ushered in a calendar.
The hottest in history has led to record energy demand and heat-related diseases, and California mountain fires have long been affected by high temperatures.
It will exist forever. ?
First, East Asia, China and Japan all suffered from ultra-high temperature heat waves. North China suffered from historical high temperature, and many places in southwest China suffered from historical hottest. South China and Jiangnan Jianghuai also suffered from heat waves in July, especially in the Sichuan Basin and the middle and lower reaches of the Yangtze River.
Encountered the strongest high temperature process in history.
The Copernican Climate Change Service Project observed that the Antarctic sea ice area reached the lowest value in the 44-year satellite data record in July, with an average of
15.3 million square kilometers, less than the average area of 9 1 to 20 years10.0 million square kilometers, about 7%, much lower than last July.
rock bottom
The above is just a microcosm of the heat wave in the northern hemisphere. If we slowly sum up the high temperature heat wave in the northern hemisphere, I'm afraid it won't last for a while.
Bind
In the three-circle circulation model, there are mainly two circulations in the mid-latitude area where heat waves frequently occur: Hadley circulation and Ferrer circulation.
The latent heat released when the air near the equator is heated and rises to form cumulus clouds pushes the upper atmosphere to move towards the polar regions, and then reaches the south latitude and the north latitude respectively.
When it sinks cold at 20 ~ 35, it forms a circulation circle, which is called Hadley circulation circle. Because water vapor condenses during the equatorial ascent.
The air sinking near 20 ~ 35 north latitude is relatively dry, and the adiabatic heating in the sinking process further reduces the air.
The relative humidity of gas, so the sinking dry atmosphere makes this latitude zone dry early and less rainy, becoming a global subtropical high zone, the whole world.
Most deserts are located in this high pressure area. Due to the change of circulation mechanism in Qinghai-Tibet Plateau, a seasonal atmosphere has been formed in China.
Wait, not most of them have become deserts.
2. However, the western Pacific at the same latitude is still controlled by the subtropical high, and it is extremely strengthened, occupying most of China.
We can feel the same super drought and high temperature as other areas in the same latitude.
Under the action of geostrophic bias, the airflow from the lower subtropical high to the high latitude is biased towards the southwest wind in the northern hemisphere and the southwest wind in the southern hemisphere.
Northwest wind. Warm air flow from low latitude meets cold air flow from polar high pressure near latitude 60, forming a polar front.
And slide upward on the cold air, and after reaching the upper troposphere, it is divided into two parts, north and south, and some airflow has a north wind component (northern hemisphere) or
The south wind component (southern hemisphere) winds back to the subtropical high, forming a circulation circle opposite to Hadley's circulation circle, which we call it.
It's the Ferrer cycle.
In Ferrer's circulation circle, westerly winds prevail, also known as westerly belts. The west wind has many west wind fluctuations, also known as Rossby waves or lines.
There are three kinds of fluctuations in the westerly belt of the star wave, namely, ultra-long wave, long wave and short wave. These fluctuations are usually characterized by high-pressure ridges, low-pressure troughs,
There are forms of blocking high pressure or cutting off low pressure. They are one of the ways of atmospheric heat exchange between low latitudes and high latitudes.
3. Compared with the North Atlantic, China is equivalent to the downstream of the westerly belt, so the activities of the westerly belt will extend from the North Atlantic to the Arctic Ocean in northern Europe.
However, it has affected the land and sea surface temperature anomalies in China, the North Atlantic and the Arctic Ocean this spring, plus the strong temperate cyclone in the North Atlantic.
Its development has an influence on westerly jet, forming a ridge of high pressure and a trough of low pressure with strong fluctuation. When meridional circulation prevails in the westerly belt, a strong ridge of high pressure enters our country, which leads to abnormal warmth in most parts of our country, as if summer came overnight.
In April and May, due to the frequent fluctuation of the west wind, the ridge of the trough changed, and a large amount of cold air entered our country with the west wind trough, which made me
Most parts of the country, especially the cold states, make people feel as if there is no summer this year.
However, there is a strong ridge of high pressure from it.
When the sub-region entered China, North China was affected by the very dry and hot downward flow from Central Asia, and a rare high temperature day appeared.
Gas, break the illusion of no summer.
By this year, zonal circulation prevails in the westerlies, and there is no strong trough of low pressure that will occupy the subtropical high in China.
On the contrary, the frequent cold vortex activity in the westerly belt of East Asia makes it impossible for the subtropical high to move northward, as if it were fixed to the south of Jianghuai in China.
Area, combined with the western Pacific subtropical high and the high pressure in other parts of the world (such as Iranian high), has brought influence to southern China.
Powerful high temperature.
4. It can be said that the intensity, stability and persistence of subtropical high this year should be one of the strongest in recent years, which is similar to it.
Strong and high temperature weather also occurred in the south of the Yangtze River on 20 13 and 20 17. And this year's continuity, through
The circulation phenomenon of several subtropical high systems is very rare in history. This "global subtropical high belt"
Continuation is also an important reason for the high temperature intensity this year.
Of course, the strong South Asian high is also to blame. South Asia High, also known as Qinghai-Tibet High, is the strongest and most stable high in the upper troposphere in summer.
The largest range of high pressure. Although it was generated in the subtropics.
However, it is not completely consistent with the dynamic nature and mechanism of the general subtropical high.
Nevertheless, the subtropical high generally appears at a height of 500 hectopascals, while the South Asian high generally appears at a height of1000 hectopascals.
Observe. On the one hand, the intensity of South Asia high is unusually strong this year, because the Qinghai-Tibet Plateau is warmer and the melting snow on the plateau is increasing, which is also the reason.
One of the consequences of global warming. The strength of the South Asian high also means that it can give energy to the subtropical high in the middle troposphere and make it stable.
In China, it continues to cause high temperature and drought.