What is a "heat wave"?

The heat wave sweeping the world has not completely receded. The confusion of scorching sun, scorching sun and unbearable heat still makes people feel scared. The heat wave has brought disaster to the society and left us with many profound thoughts. ...

Heat wave and its characteristics

Heat wave refers to an unusual period of weather, which makes people feel uncomfortable in order to maintain excessive heat. Usually refers to the high temperature weather that lasts above 35℃ in summer, and is often accompanied by excessive humidity. This term is usually associated with a region. A normal temperature for a warmer climate region may be a heat wave for a usually colder region.

Heat waves usually last for several days or even weeks, which will make people's endurance exceed the limit and lead to death. Heat wave is an extreme weather event, which occurs frequently all over the world and has great influence. In big cities all over the world, thousands of people die every year because of heat waves.

Since 1990s, high temperature and high humidity weather has also appeared frequently in summer in China. After 1994, 1997 and 1999, the summer heat was unbearable, and people still remember it. The hot and humid weather in 2000, 2002 and 2004 is also unforgettable. The heat wave in China is increasing, especially in the north. In the summer of 1999, there were two periods of continuous sunny, hot and high temperature weather in North China and its surrounding areas, and the number of high temperature days greater than or equal to 35℃ was generally 10-25 days; On July 24th, the highest temperature in Beijing reached 42.2℃, the highest temperature since the founding of the People's Republic of China. In the summer of 2000, many areas in North China and South China were hit by heat waves, and the days of high temperature above 35℃ in Chengde, Hebei, Beijing and Lianxian, Guangdong reached 28, 26 and 44 days respectively. Chengde, which is famous for its cool summer, has a maximum temperature of over 40℃ for three consecutive days from July 12 to July 14, with the maximum temperature of 43.3℃ on July 14.

This summer, the rolling heat wave swept the world, and the temperature in many countries and regions exceeded the extreme value of decades or even centuries, and the degree of drought was extremely rare. The heat wave swallowed thousands of lives, tens of millions of animals died and hundreds of thousands of people fainted or were hospitalized. More than a dozen provinces and cities in China such as Shaanxi, Shanxi, Anhui, Hubei, Chongqing, Sichuan, Guizhou, Yunnan, Gansu, Ningxia, Hunan, Nanjing and Hanshui Valley were hit by high-temperature heat waves. Since June, the number of high temperature days in various places is generally around 25-30 days. In some places, for more than 40 consecutive days, especially since July 10, Chongqing, eastern Sichuan, southwestern Shaanxi and other places have been hit by rare continuous high-temperature heat waves. The days of high temperature are more than normal 15-25 days, and the days of daily maximum temperature above 40 degrees in Chongqing and other places are more than 5- 12 days, which is rare in the same period in history since meteorological records were recorded. On August 15, the highest temperature in 29 districts and counties in Chongqing exceeded 40 degrees, and the temperature in 6 districts and counties exceeded 43 degrees. Among them, the highest temperature in Qijiang County reached 44.5 degrees, a record high, and the highest temperature and heat wave days in Chengdu continued to break through the record high. On August 1 day, the extreme high temperature of 47.7 degrees reappeared in Turpan. On August 3, the highest ground temperature at Turpan Station was as high as 75. 1 degree. In June, the highest temperature in Hanzhong, which is known as the small south of the Yangtze River in the northwest, all counties and districts in the city 10 exceeded the historical extreme value in the same period. In mid-July, the average temperature in nine counties in the city exceeded 3 16 degrees, the highest in the same period since the station was established. By August, the number of days with high temperature above 35 degrees actually appeared 170 times.

Chongqing and Sichuan are the heaviest in 50 years. More than 30 million people and livestock have difficulty drinking water. In the flood season, the lowest water level in history appeared for the first time in Chongqing section of the Yangtze River: 4.92 meters, 80% of the rivers were cut off, the high temperature and drought continued, the prices of vegetables and many articles related to life rose, the vegetation in the forest dried up, and forest fires occurred frequently. These data show that heat wave has become one of the main meteorological disasters in summer.

Why do heat waves occur so frequently in recent years? First of all, global warming is the big climate background of high temperature heat wave. In the past century, the earth's climate is undergoing significant changes characterized by global warming. This global warming is caused by natural climate fluctuation and the greenhouse effect aggravated by human activities. Global climate change is accompanied by the increase in the frequency and intensity of heat waves, and it becomes hotter in summer. Secondly, due to the acceleration of urbanization, the decrease of vegetation, the increase of urban population density, the urban heat island effect is more obvious, and the extreme high temperature is also increasing. Some experts believe that the formation of high temperature weather, in addition to global warming and greenhouse effect, is also closely related to excessive solar radiation caused by ozone layer destruction.

Heat waves are periodic and sporadic. There are frequent heat waves in summer every year, but the area, time, frequency and intensity of heat waves are constantly changing, and this change is the biggest in the mid-latitude area, which makes the cities in the mid-latitude area most sensitive to heat waves. Due to people's climate adaptability, the influence of heat wave in early summer is greater than that in late summer.

The impact of heat wave on cities is much greater than that on suburbs and rural areas. Because of the urban "heat island effect", the urban temperature is not only high but also persistent, and the influence of thermal intensity and duration on mortality is greater than the instantaneous maximum temperature. Air pollution in urban areas is also more serious, and heat waves are usually associated with high pollution levels. For example, during the 1995 heat wave in the United States and Wales, it is estimated that more than half of the deaths were caused by the aggravation of air pollution at that time.

Heat wave and human health

The heat wave has a great influence on the human body. Heat wave disease caused by heat wave can be divided into heatstroke and heatstroke.

Heatstroke mostly occurs in dry and hot weather. Because the infrared ray with the wavelength of 600- 1000 mm in solar radiation can penetrate the skull, the temperature of brain tissue suddenly rises, resulting in the impairment of cranial nerve function. The main symptoms are severe headache, dizziness, irritability, tinnitus, nausea, vomiting and cardiopulmonary dysfunction.

Heatstroke is the sudden rise of skin temperature under the attack and stimulation of damp-heat waves, which makes the heat dissipation function of the skin decline, so that the heat in the body cannot be distributed. Infrared rays and ultraviolet rays can penetrate the skin directly to the deep muscle, causing skin dryness and muscle temperature increase, which in turn affects the functions of various organs and tissues of the whole body, resulting in local muscle spasm, fever, dry mouth, cough, asthma, dyspnea, elevated blood pressure and respiratory failure.

The most direct impact of heat wave on human health is the increase of morbidity and mortality. In cities such as the United States, Canada, New Zealand and Greece, when heat waves hit, the overall mortality rate showed an upward trend. Shanghai 1998 experienced the worst heat wave in recent decades, and there were four heat waves of more than three days in the whole summer (July 8-20, August 1-3, August 7- 17, August 2 1-23). Heat waves are also a great threat to babies. If babies suffer from certain diseases, such as diarrhea, respiratory infection and mental retardation, they are most vulnerable to high temperature during the heat wave. In addition to the direct impact of heatstroke death, the increase of heat wave intensity and duration will also lead to diseases or deaths mainly in the heart and respiratory system.

The influence of heat wave on human health is also related to urban living conditions, socio-economic factors and preventive measures. Urban living conditions are an important risk factor. Living on the top floor, downtown and residential areas without air conditioning environment has high morbidity and mortality. Social and economic factors, including the gap between the rich and the poor, social contact and education level, are also influencing factors.

However, high temperature is not the whole of this disastrous weather. Another terrible thing is that this kind of weather may push all kinds of diseases that were originally hidden in the tropics to the high latitudes of the earth. This is because the heat wave has changed the climate environment in high latitudes, so that some microorganisms and animals that spread tropical diseases can also thrive in high latitudes, making some high latitudes become hotbeds of tropical diseases.

Studies show that malaria will spread to a wider area by the end of this century. It is caused by plasmodium and spread by mosquitoes. According to statistics, every 30 seconds, one person in the world is infected with malaria. By 2080, some areas without malaria today, such as the Pacific coast of the United States, parts of southern Scandinavia and Siberia, will become malaria epidemic areas, and residents there will live at risk of malaria infection for 1 ~ 3 months every year. Other parts of the world, such as eastern China, central Europe and Ohio Valley in the United States, will also become more suitable for malaria transmission, and the annual malaria transmission time will be much longer than it is now.

Another disease that can spread in hot weather is asthma. In the United States, the number of people suffering from asthma reaches 6.5438+0.6 million every year, and the number of children suffering from this disease is also increasing. There are many factors that lead to asthma attacks. A certain amount of pollen and fungal spores in the air can stimulate asthma attacks, and the increase of pollen and fungal spores in the air is closely related to the concentration of carbon dioxide. In the future hot air, the concentration of carbon dioxide will be quite high. The results showed that with the increase of carbon dioxide concentration 1 fold, ragweed which can produce a large number of pollen increased by 10% and its pollen increased by 60%. These pollen and fungal spores like to adhere to tiny pollutants in exhaust gas. Compared with just breathing pollen and spores, this kind of pollen and spores combined with pollutants will bring more serious lung and respiratory diseases to people.

Monitoring and health care of heat wave

Heat waves can be monitored and warned, and many cities in China and even around the world have issued warnings of high temperature or heat waves. According to the regulations of China Meteorological Bureau, the daily maximum temperature is predicted to be above 35℃; In this summer's heat wave, Sichuan issued a first-class red warning, and more than a dozen cities issued high-temperature orange warnings. The national weather bureaus of the United States, Canada, Israel and other countries have issued high temperature warnings based on the thermal index (also known as apparent temperature) that comprehensively considers the influence of temperature and relative humidity. When the predicted thermal index exceeds 40.5℃ for three consecutive days or the predicted thermal index exceeds 46.5℃ at any time, the National Weather Service will issue a high temperature warning. Other cities that have established similar heat wave and health monitoring and early warning systems include Toronto, Canada, Dayton, Ohio, Cincinnati, Columbus and Phoenix, Arizona. The Climate Committee under the World Meteorological Organization has set up an expert group to promote the heat wave and health early warning system, and plans to establish similar heat wave early warning systems in Casablanca, Morocco and Europe. German scientists developed the human physiological equivalent temperature (PET) based on the human thermal balance model. When PET exceeds 465,438+0℃, the thermal mortality rate increases significantly, which can also be used for heat wave monitoring and early warning. When the heat wave comes, people can effectively take various adaptation measures to greatly reduce the possible impact of the heat wave on health. The most important and effective measures are sound public health infrastructure, perfect heat wave early warning system and appropriate heat wave emergency response strategy.

In hot summer and heat wave weather, people should try to avoid physical labor or participate in more intense sports activities, let alone stay in the scorching sun or high temperature environment. If you want to go out, you should put on your hat and umbrella. Secondly, the bedroom should be ventilated and the ground should be kept cool. It is best to put curtains on the windows in Chaoyang to ensure adequate sleep. Third, eat more fresh vegetables, fruits, salt water, mung bean soup and sour plum soup. Fourth, clothes should be light, loose, light in color, easy to absorb sweat, and breathable, and should be changed frequently. Fifth, keep an optimistic mood. Keep some Huoxiang Zhengqi Water and Ren Dan at home and take them at the right time. Sixth, if there are patients at home, they should immediately lie down in a ventilated and cool place and drink plenty of water. Or take a warm bath immediately, or wash warm water first and then cold water. Those with severe symptoms should go to the hospital immediately.

The heat wave tests the level of government management.

The attack of heat wave has brought all kinds of confusion to the public's production and life, and even affected the public's life safety to a certain extent. It is reported that the public lost their precious lives under the attack of heat wave last year. Therefore, the heat wave tests the government's responsibility, normal management level and crisis management. In the face of the heat wave, although we have seen dozens of cities such as Beijing repeatedly issue orange and red high-temperature warnings, and governments at all levels are actively trying to solve many difficulties in the production and life of ordinary people in high-temperature areas, we believe that from the perspective of government responsibility, the government should do more in many aspects.

Because, effectively resisting the heat wave attack is related to the safety and interests of the public, as well as the vital interests and life safety of citizens. And the government has the responsibility to bear the risk of public safety. However, when examining the government's public service function in response to the heat wave, I regret to find that the government's social management and public service functions are still relatively weak, and there are still many outstanding problems to be solved urgently. For example, whenever a turning point or sudden disaster weather comes, our information cannot be released to the society in time through government media or effective means to achieve the purpose of reducing losses. As far as social management is concerned, China's traditional social management model is a centralized management model with a high degree of integration of government and society, which leads to the lack of self-management and self-development ability of society and affects the coordinated and healthy development of society. In other words, we are vulnerable to heat waves. The whole management system, including the managers of government departments, is "more willing" to believe that there is no danger and safety every day, and is used to planning and carrying out work under normal conditions. However, there is always uncertainty in the management environment, and unpredictable crises are inevitable. Therefore, the specific crisis management mechanism in China is also very fragile, lacking a complete emergency system that comprehensively covers all kinds of crises. Once it encounters a "new" crisis, it feels at a loss. For example, this summer's heat wave made it difficult for tens of millions of people to store drinking water; Every day, hundreds of thousands of people can't turn on the air conditioner because of lack of electricity; The problem of millions of ponds and reservoirs drying up; Millions of kilograms of fish died; Price increase of daily necessities. , is at a loss to the government. In reality, crisis management is carried out by industries and departments. Although it is conducive to the realization of "division of responsibilities", when there is a "comprehensive" crisis that requires multiple departments to deal with together, it will produce high coordination costs and seriously affect the response speed. In fact, this fragility is also a microcosm of the fragility of the whole public management system in China. Facing the heat wave, we should realize that the government plays an authoritative role and bears the core responsibility. The essence of local public management and social public service is how the government becomes a responsible, effective and transparent government. However, for a long time, governments at all levels have not paid enough attention to the signs of social public crisis. Due to the long-term compartmentalization and administrative management mode, there is a lack of effective cooperation and cooperation between local governments and a lack of mechanism to deal with emergencies. When a crisis occurs in the area where a local government is located, other governments become bystanders. For example, during the rainfall in Hanzhong at the end of July and the beginning of July, some leaders did not know enough about the drought and high temperature in Hanzhong and paid insufficient attention to it. Municipal people's office wants to seize the favorable opportunity to carry out artificial precipitation enhancement. The leaders of local governments in many counties were lucky and did not actively support them, which led to some places in Pingchuan missing the opportunity of rainfall and causing severe drought in the later period. Therefore, we sincerely expect governments at all levels to show their management wisdom in the face of the heat wave. They must regard public safety as the main function of the government, pay attention to the construction of public facilities at ordinary times, and think more about the people, that is, do everything possible to benefit the public.