China's air index is divided into several grades.

Air pollution index (API) is to simplify the concentrations of several air pollutants routinely monitored into a single conceptual index value, which represents the degree of air pollution and air quality in different levels, and is suitable for representing the short-term air quality status and changing trend of cities.

Air pollution index is to determine the classification value of pollution index and the corresponding pollutant concentration limit according to the air environmental quality standards and the ecological environmental effects of various pollutants and their impact on human health. The air pollution index grading standard adopted by the weekly air quality report is: (1) The pollutant concentration corresponding to 50 points of the air pollution index (API) is the first-class standard of the national air quality daily average; (2) The pollutant concentration corresponding to API100 is the national secondary standard of daily average air quality; (3) (3) The pollutant concentration corresponding to API 200 is the national daily average level 3 standard of air quality; (4) (4) The classification of the higher value section of API corresponds to the concentration limit when various pollutants have different effects on human health.

According to the characteristics of air pollution in China and the key points of pollution prevention and control, the items currently included in the air pollution index are tentatively sulfur dioxide, nitrogen oxides and total suspended particulate matter. With the deepening of environmental protection and the improvement of monitoring technology, other pollution projects will be adjusted and increased to reflect the pollution situation more objectively.

At present, the air pollution index (API) adopted in China is divided into five grades, and the API value is less than or equal to 50, which means that the air quality is excellent, which is equivalent to reaching the first-class national air quality standard and meeting the air quality requirements of areas requiring special protection such as nature reserves and scenic spots. The API value is greater than 50 and less than or equal to 100, which means that the air quality is good, which is equivalent to reaching the second-class national air quality standard. The API value is greater than 100 and less than or equal to 200, indicating that the air quality is slightly polluted, which is equivalent to reaching the national air quality third-class standard; After long-term contact, the symptoms of susceptible people are slightly aggravated, and healthy people have irritating symptoms. The API value is greater than 200, indicating that the air quality is poor, which exceeds the national air quality level 3 standard and is harmful to human body after exposure for a certain period of time.

API range of air pollution index and corresponding air quality categories

Air pollution index air quality category air quality description's impact on health.

0-50 grade I excellent normal activities.

51-100 Ⅱ is good and normal.

10 1-200ⅲ light pollution is exposed for a long time, and the symptoms of susceptible people are slightly aggravated, and healthy people have irritating symptoms.

2065438+0 ~ 300Ⅳ moderate pollution exposure for a certain period of time, the symptoms of patients with heart disease and lung disease are obviously aggravated, and the exercise tolerance is reduced, while the healthy people generally have symptoms.

& gt300 ⅴ The exercise tolerance of heavily polluted healthy people is reduced, the symptoms are obviously strong, and some diseases appear in advance.

"Rain and snow coexist" phenomenon: Nanjing, Yangzhou, Taizhou and other areas along the Yangtze River snow, Shanghai, Hangzhou, Suzhou and other coastal areas rain. When we look at the weather forecast, it is only a few simple words, such as whether it is sunny or rainy and what the temperature is, but making a forecast requires a very complicated process.

The first is to collect meteorological data, from the ground to the sky, from the land to the ocean, to observe atmospheric changes in an all-round and multi-level way, and quickly collect observation data.

Secondly, the computer processes and calculates the collected data to obtain weather charts, numerical forecast charts and other products, which provide forecasting basis for forecasters.

Third, professionals analyze the data and make preliminary predictions. There are many methods of weather forecast, and there are two most commonly used.

One is the traditional synoptic method, which analyzes various meteorological elements on the weather map and makes weather forecast.

The other is numerical prediction method, which is "calculated" by computer. Because the motion of the atmosphere follows some known physical laws, the motion state of the atmosphere can be written as a set of partial differential equations. Given the initial value (the current state of the atmosphere), the variable values of the equations can be solved over time, and the future state of the atmosphere can be obtained.

Fourth, the final conclusion. Both synoptic methods and numerical prediction methods have certain limitations, and the prediction conclusions are different. At this time, based on theoretical knowledge, accumulated experience and corresponding wisdom, forecasters sometimes reach more reliable prediction opinions through multi-person consultation.