The deterioration of air quality is strongly related to the meteorological condition. A better understating on the microscale, mesoscale, and PBL meteorology can effectively help the implement of air quality forecast and analysis. In the past decades, the Southeast Asia has experienced remarkable economic and population growth. The large increase in various types of factories, human activities, and biomass burning decreased the air quality over this region. The local air pollution of Taiwan gets more attention recently. High PM2.5 concentration events occur frequently in Central and Southern Taiwan, not only due to the emissions but also the weak atmospheric diffusion condition. Therefore, understanding the thermodynamics structure within PBL can help to clarify the cause of deteriorating air quality. Although the EPA Taiwan Air Quality Monitoring network provides the air quality information at the ground level, it cannot explain the PM2.5 characteristics in vertical. Therefore, observing the aerosol optical characteristics in the vertical direction by using remote sensing techniques, which can monitor the change of pollutants over time and space, is complementary for air quality monitoring. The objectives and task of this project are: (1) to continue the conduct of international collaborations cooperation with NASA MPLNET and AERONET, and technical consultation and data exchange; (2) to strengthen the abilities to replace components that improve the accuracy of observation, also holding the training course for stations and equipment maintenance; (3) to offer professional consultation on micro-pulse lidar systems and sun photometers, evaluation of related equipment, and environmental safety information about the stations; (4) to build the lidar observation database and accomplish the operations of data QA/QC; (5) to integrate the observational data based on EPA MPL systems and air quality monitoring station, and further analyze the possible causes of high pollution events, also export its potential on air quality forecast; (6) to develop the method of estimating boundary layer height, and analysis the relationship between chemical characteristics of aerosols and depolarization ratio. The important achievements from this project are listed as follows: • We continued to cooperate with NASA MPLNET and AERONET. We used online meeting and physical meeting in Taiwan with the chair of MPLNET, the chair of AERONET, and the main engineering staff for discussing data retrieval techniques, calibrating the WFR equipment, and educating the techniques on calibrating and replacing components. • We also hold the training course for stations and equipment maintenance. We maintained the four MPL and Sun-photometer stations over Taiwan, including the regular maintenance, monthly calibration, and local staffs training. • We had executed the AP/DC calibration and data QA/QC procedure on schedule to ensure the availability and stability of MPL data. The MPL data has been posted to webpages and database real time and update to EPA server simultaneously. • We applied a statistical method to define the high pollution events in this year and set up a database for case studies. We systematically analyze those pollution events with observational data obtained from EPA MPL system and air quality monitoring stations in Taiwan. We explained the causes of high pollution events based on multiscale analysis including vertical and horizontal distribution of particulate matters and meteorological conditions. The results from those case studies significantly improve our understanding on the air quality deterioration. • We provided the preliminary research of analyzing boundary layer height seasonal characteristics in the southern Taiwan. We analyzed the chemical characteristics of aerosols with lidar depolarization ratio.

Micro-pulse lidar (MPL), Sun photometer, International collaboration