## 2 Data and Model Experiment
### Emission Inventory and Scenarios
#### 2.2.2 Emission Scenarios  
Because the major and easily controlled sections had been regulated during the 12 th Five-Year Plan period (12 th FYP), the 13 th FYP emission control policy was set more aggressively: industries generating air pollution will be moved out from the central city area, ultraclean/effective technology will be widely used, the ratio of public transport will rise to 70% of motorised travel [12], electric buses will be applied widely, accounting for 63% of public buses [54], vehicle emission standards and fuel standards will be strengthened (specifically, eliminating high pollution vehicles, implementing the new national emission standard of vehicle and the new national vehicle fuel standard, etc. ), and VOC emission will be controlled entirely in particular industries (e.g., chemical industry, paint industry, and printing industry, etc.) [49]. Four scenarios were designed to evaluate the impact of the 13 th FYP on the air quality in Haizhu district in 2020. The meteorological conditions were assumed to be unchanged, which means that the meteorological conditions in 2015 were used for all scenarios in 2020. The four 2020 scenarios are as follows (also in Table S2):  
Scenario 2020A was proposed such that both Haizhu emission control policy and Guangzhou (except Haizhu) emission control policy would follow the 2015 emission control policy tendency. This scenario is a baseline scenario. Scenario 2020B was designed such that Haizhu emission control would be implemented based on the 13 th FYP emission control plan, while Guangzhou (except Haizhu) would still adhere to the 2015 emission control policy. Scenario 2020C was a 13 th FYP policy scenario in which both Haizhu emission control policy and Guangzhou (except Haizhu) emission control policy would be implemented based on the 13 th FYP emission control plan. Scenario 2020D was a scenario for vehicle control in Haizhu due to the significance of vehicle emission in Haizhu. In this scenario, vehicle control in Haizhu would be implemented based on the 13 th FYP emission control plan, while other emission source controls in the Haizhu and Guangzhou (except Haizhu) emission control policy would remain as the 2015 emission control policy tendency. We note that the contribution of vehicle emission in Haizhu district is \(<\)10% of that in Guangzhou city. Table 1 shows the changes in emissions of SO\({}_{2}\), NO\({}_{x}\), CO, PM\({}_{10}\), PM\({}_{2.5}\), and VOCs for the different scenarios in the whole city of Guangzhou. The 2020A, 2020B, and 2020D scenario emissions would be higher than the 2015 emissions (SO\({}_{2}\), NO\({}_{x}\), CO, PM\({}_{10}\), PM\({}_{2.5}\), and VOCs would increase 57.2-58.9%, 47.4-48.6%, 60.1-60.2%, 14.6-15.1%,25.8-26.4%, and 24.9-25.0%, respectively), whereas the 2020C scenario emission would be lower than or roughly equal to the 2015 emission. The difference of  
emissions among each scenarios indicates that the emission control of the whole Guangzhou city would significantly affect the 2020 emission. Additionally, the emission ratio (VOCs/NO\({}_{x}\)) would be around 0.72 in scenarios 2020A, 2020B, and 2020D and 0.60 in scenario 2020C, lower than 0.86 in 2015. The changes in emissions for each sector are shown in Figure 2. SO\({}_{2}\) emission from the sectors residential, vehicle, and others, and NO\({}_{x}\) emission from the residential sector in the four 2020 scenarios would be lower than those in the 2015 emission. PM\({}_{2.5}\) emission and PM\({}_{10}\) emission from the residential sector in scenarios 2020B and 2020C would also be lower than those in the 2015 emission. In scenarios 2020C, NO\({}_{x}\) emission from the vehicle and others sectors, CO emission from the industry, residential, and vehicle sectors, and VOCs emission from the residential sector would be higher than those in the 2015 emission.