What is heat island intensity?

The heat island intensity refers to the temperature difference between two representative measuring points in the heat island effect.

The comprehensive effects of urban population density, heat exhaustion of factories and vehicles, energy release of residents' daily life, urban building structure and underlying surface characteristics are the main reasons. The intensity of heat island has obvious diurnal and seasonal variations. The diurnal variation is strong at night and weak during the day, and the maximum value appears on a clear and windless night. The maximum heat island intensity observed in Shanghai is above 6℃.

Seasonal distribution is also related to urban characteristics and climatic conditions. Beijing is the strongest in winter, the weakest in summer and the middle in spring and autumn. Shanghai, Guangzhou 10 is the strongest. The annual average temperature difference between urban and rural areas is about 65438 0℃, such as 0.7 ~ 65438 0.0℃ in Beijing, 0.5 ~ 65438 0.4℃ in Shanghai and 0.5 ~ 65438 0.5℃ in Los Angeles.

The intensity of heat island mainly shows two periodic changes with time, namely, daily change and annual change. In sunny and windless weather, the diurnal variation is strong at night and weak at noon during the day; The annual change is strong in autumn and winter and weak in summer. The intensity of urban heat island not only changes periodically, but also has obvious aperiodicity.

The reasons for the non-periodic change of heat island intensity are mainly related to the wind speed, cloud cover, weather situation and low-altitude temperature drop rate at that time. The main performance is that the greater the wind speed, the more clouds, the more unstable the weather situation, the greater the direct drop rate of low-altitude temperature, the smaller the intensity of heat island, and even no heat island, and vice versa.

Main hazards of extended data

1, a large number of pollutants gather in the center of the heat island, and the concentration increases sharply, which directly stimulates human respiratory mucosa, causing cough and runny nose in light cases, and respiratory diseases in severe cases, especially middle-aged and elderly people with chronic bronchitis, emphysema and asthma, with high mortality. For example, in London, England, more than 4,000 people died in 1952+02.

2. Air pollutants can also irritate the skin, leading to dermatitis and even skin cancer. Some substances, such as chromium, will irritate the conjunctiva, cause inflammation and even lead to blindness if they enter the eyes. High levels of mercury can damage people's kidneys and cause severe abdominal pain and vomiting. Chronic mercury poisoning can also damage people's nervous system.

3. People who live in the central area of the heat island for a long time will show emotional irritability, listlessness, depression, memory loss, insomnia, loss of appetite, indigestion, aggravation of ulcers, recurrence of gastrointestinal diseases, etc. This will bring untold troubles to the work and life of city people.

4. The main influence on residents' life and consumption is the heat island effect in high temperature weather in summer. In order to reduce the indoor temperature and make the indoor air circulate, people use air conditioners, electric fans and other electrical appliances, which consume a lot of electricity. For example, in 20 12 years, the electricity consumption of the United States16 was used for cooling, so the annual electricity bill was 40 billion dollars. High temperature weather also has adverse effects on human health.

5. Relevant research shows that when the ambient temperature is higher than 28℃, people will feel uncomfortable; No matter how high the temperature is, it is easy to cause symptoms such as irritability, heatstroke and mental disorder; If the temperature continues to be higher than 34℃, it can also lead to a series of diseases, especially cardiovascular and cerebrovascular diseases and respiratory diseases, and the mortality rate will increase significantly.

Baidu Encyclopedia-Heat Island Effect

Baidu encyclopedia-urban heat island