EPA \ TAQMN \ Air Quality Monitoring \ Air Quality Forecast


1. Evolution of Forecast Operations

In order to get the general public to understand the air quality of their surrounding environment for reference when doing outdoor activities, this administration conducts daily air quality forecast operations using the air quality index (AQI) forecast to provide the public with information to allow them to take appropriate preventive measures.

The air quality forecast has an effective period of 24 hours and focuses on Taiwan's main pollutants: PM10 , PM2.5 and O3. The forecast assumes that the changes in daily pollution emission is far lower than changes in the weather, and forecasts next day air quality due to elements of weather. The development of these operations are detailed below:

  1. Experimental Forecast Period

  2. During the mid 80s, the administration determined from monitoring data from each region that due to Taiwan's swift industrialization and urbanization, air quality in regions showed a deteriorating trend. Therefore, the “Emergency Preventative Measure to Address Deteriorating Air Quality Draft Plan” was proposed to determine the severity level of air pollution events to use as evidence for announcing warnings for severely deteriorated air quality. Hence, the “Air Pollution Warning Specialist System” began development.

    Studies showed that changes in air quality were closely linked to weather type which is why statistical forecasts of air pollution was developed, categorizing weather that affects Taiwan into 8 major types and uses subjective figures to come up with a forecast graph along with ground wind speed to form a regression analysis of the PM10 density of the greater Taipei and Kaoshiung regions. From this, we can grasp approximately 50-60% of high pollution weather types. Better forecast results can be gained by forecasts using statistical regression of borderline weather indexes that give additional weight to weather types with high pollution characteristics

    At this stage the air quality forecast operation evolution of each region in Taiwan proceeded as below:

    (1)Starting in 1991 air quality focusing on PM10 is used to forecast the next day air quality of the Taiwan region.

    (2)In August of 1991, the Kaoshiung area was included in the forecast.

    (3)In April of 1993 the O3 forecast of Taipei and Kaoshiung areas were included.

  3. Developmental Phase
  4. The air quality monitoring station network was fully updated in September of 1993 and eight air quality areas were divided in Taiwan while the administration reassessed the PM10 density weather regression analysis of the greater Taipei and Kaoshiung regions, re-categorizing weather into 19 different types.

    New air quality forecast techniques were developed as local weather operations and research progress. Each of the air quality forecast areas were targeted and new methods of forecast were established such as the multiple regression method, CLIPER (climate, continuous) method, high pollution weather type analogy method to obtain a next day air quality forecast. Simultaneously supplementary man to machine communication type air quality software was developed to support forecast personnel in their tasks.

    At this stage the air quality forecast operation evolution of each region in Taiwan proceeded as below:

    (1)66 air quality monitoring stations were completed in 1993 which used controlled air quality districts as basis to reference weather districts and divided Taiwan regions according to air quality monitoring stations and pollution characteristics. Taiwan was divided into 8 regions: Taipei Keelung, Taoyuan Zubei Miaoli, Taichung Changhwa, Nantou, Yunlin Chiayi, Tainan Kaoping, Yilan, Hualien Taitung.

    (2)Forecast of Taipei Keelung and Tainan Kaoping began in December of 1993.

    (3)Forecast of Taichung Changhwa began in October of 1994.

    (4)Forecast of Hualien Taitung began in March of 1995.

    (5)Forecast of Taoyuan Zubei Miaoli and Yilan regions began in October of 1995.

  5. Mature Phase
  6. Current air quality forecast methods were established in 1998. As Taiwan's air quality monitoring station network was updated in 1993, the original methods of data collection in terms of weather, and the air pollution databases also needed to be reestablished. However, in order to establish statistics, more representative samples were needed which is why this administration continued to improve statistical regression formulas to update CLIPER's statistical values; also, focusing on high pollution events related to PM10 and O3, analogical forecast abilities were changed as we also began to notice air pollution caused by east Asia dust storm. In this stage, aside from the improvement of analogical methods, another main result was to categorize Taiwan's weather into 53 types, grouping similar weather control mechanisms of each season into the same type to re-develop 20 types of weather graphs and identifying 7 weather types that mainly accompanied a deterioration of air quality to continue efforts in improving the man to machine communication interface of the supplementary forecast system. Weather data input was automated and using the analogical method a policy tree was displayed to facilitate the operation of forecast personnel.

    At this stage the air quality forecast operation evolution of each region in Taiwan proceeded as below:

    (1)Forecast operations of next day PM10 and O3 values for all of Taiwan while forecasts for Nantou, Chiayi regions were added in 1996.

    (2)Using air quality conditions and air quality control districts as basis and referencing the air quality monitoring station and pollution source dispersion in Taiwan, the regions were adjusted to 8 regions: Taipei, Taoyuan Zubei Miaoli, Taichung Changhwa, Nantou, Yunlin Chiayi Tainan, Kaoping, Yilan, Hualien Taitung.

    (3)PM10, PM2.5 and O3 air quality index forecast services were provided through the Internet and mas media outlets for the general public to use as reference for outdoor activities. Also, the air pollution control methods of various environmental agencies were provided for reference.

  7. 8 Hour Forecasts of PM2.5 and O3
  8. In order to further protect the health of those sensitive to air pollutants, the administration added 76 PM2.5 air quality automatic monitoring instruments in August of 1995 to obtain instant detection of PM2.5 density in the air.

    After consulting related experts and scholars on current PSI and referencing the World Health Organization's (WHO) global air quality guideline and America's air quality index, the current PSI forecast system was kept but the 8 hour PM2.5 and O3 warning index was added. The former warns at values above 65μg m-3 while the latter warns at values larger than 80 ppb to put in place a warning mechanism for those who are sensitive. Forecast began in July of 1997 and forecast regions were adjusted to 7 air quality regions.

  9. 3 Day Air Quality Forecast
  10. In order to further share government resources to achieve the effect of inducing synergistic effects of various agencies and supplementary information, the administration strengthened ties with the Ministry of Transportation and Communications and the Central Weather Bureau in 1997 and 1999 by signing agreements. By improving relations, air quality forecast technology and remote satellite technologies were improved and applied in environmental monitoring, establishing environmental weather information systems and other tasks to support the operation needs of environmental quality monitoring and fully expressing the application uses of weather information.

    According to the cooperative results of 97, the weather bureau began to provide this administration with a 72 hour medium weather forecast product in 98, consolidating this administration's air quality forecast supplementary system extending the next day air quality forecast (24 our) to a 3 day (72 hours) forecast which included PM10, ozone PSI, 24 hour PM2.5, and an 8 hour ozone warning index to further provide the general public with pollution control for reference in their outdoor activities.

    In December of 2016, forecast were adjusted to air quality index(AQI).

2. Forecast Operations Summary

  1. Data Collection
  2. 1. WINS

    Weather information is obtained through this administration's monitoring resources which are connected to the Central Weather Bureau's mainframe, using the WINS system's various options such as ground weather graph, high altitude weather graph, satellite cloud graph, and radar graph. Also, the weather graphs produced through the WINS system's various indexes can be added and played to analyze local circulation and weather conditions.

    2. WRF Forecast Information

    The Central Weather Bureau began providing this administration with 72 hour medium weather forecast products (WRF, weather research and forecasting) which included information on rain fall, atmospheric pressure, altitude, comparative humidity, vorticity, wind field, and temperature fields for east Asia, south China, Taiwan, northern Taiwan, mid Taiwan, and southern Taiwan.

    3. The Internet

    The current day's air quality weather field conditions can be determined by logging onto the Central Weather Bureau's website (http://www.cwb.gov.tw) and reading today's air quality and weather conditions. Then, the weather bureau's next day forecast can be used to analyze the weather systems affecting the Taiwan region and whether they will continue to do so, or if other weather systems are nearing Taiwan and if so when the time it will take for them to affect the region. Choosing the satellite cloud graphs of various regions and various channels including the east Asian and Taiwan regions information of infrared, visible light, and color coded cloud graphs can be obtained. Usually speaking, the satellite cloud graph can be used to affirm the weather systems of weather forecast information and the MODIS satellite currently used by the administration can be used as analytical data for aerosols, dust storm, and organic combustion. Furthermore, the forecast data obtained by the Korean and Japanese weather bureaus, American Navy, and Europe can be used as the reference data for the preparation tasks of forecasting.

    4. Air Quality Monitoring Information

    Updated and historic information can be referenced for forecasting operations by using the air quality monitoring data instant query system.

  3. Supplementary Forecast System
  4. Inputing related weather indexes into the supplementary air quality forecast system results in forecast indexes of climate law, continuous law, regression law, and analogical law. With the supplementary forecast system's subjective forecast indexes and forecast personnel's objective adjustments, 3 day forecasts of the PM10, ozone , 24 hour PM2.5, and ozone warning index can be obtained.

  5. Announcement of Forecast Results
  6. At 5 PM of everyday the 3 day air quality forecast is faxed to 72 major media outlets and environmental agencies. The information is also uploaded to the administration's website and voice service system for the public to peruse.

last update : 2019/11/27