## 2 Data and Model Experiment
### Emission Inventory and Scenarios  
#### 2.2.1 Emission Inventory  
The anthropogenic emissions from the 2012-based Multiresolution Emission Inventory for China (MEIC) [43] ([[http://www.meicmodel.org/](http://www.meicmodel.org/)]([http://www.meicmodel.org/](http://www.meicmodel.org/))), biogenic emission parameterisation [44], dust emission parameterisation [45], and sea salt emission parameterisation [46], and the marine emission from EDGAR (Emission Database for Global Atmospheric Research, [[http://edgar.jrc.ec.europa.eu/](http://edgar.jrc.ec.europa.eu/)]([http://edgar.jrc.ec.europa.eu/](http://edgar.jrc.ec.europa.eu/))) were applied in this study. The 2012-based MEIC was a Chinese national emission inventory with a resolution of 0.25\({}^{\circ}\)\(\times\) 0.25\({}^{\circ}\) based on 2012 emission status, developed by Tsinghua University. It included the emissions in major sectors, such as transport, industry and human residential, etc. [13]. Previous studies reported that MEIC was well developed by a technology-based emission model [47] and similar emission datasets have been widely used in the numerical simulation for cities in PRD [27; 48].  
The emissions in the key research area, Guangzhou, were obtained based on the Guangzhou ambient air quality plan (2016-2025) [49]. The emission of air pollutants from different sources in Haizhu district in 2015 was retrieved from the Guangzhou environmental protection bureau's data  
Figure 1: The Haizhu region and its location (GD: Guangdong province; PRD: Pearl River Delta; GZ: Guangzhou) [14; 41; 42].  
network ([[http://www.gzepb.gov.cn/infoindex.htm](http://www.gzepb.gov.cn/infoindex.htm)]([http://www.gzepb.gov.cn/infoindex.htm](http://www.gzepb.gov.cn/infoindex.htm))). Based on the statistics yearbook ([[http://210.72.4.52/gzStatl/chaxun/njs.jsp](http://210.72.4.52/gzStatl/chaxun/njs.jsp)]([http://210.72.4.52/gzStatl/chaxun/njs.jsp](http://210.72.4.52/gzStatl/chaxun/njs.jsp))) and the Guangzhou environmental protection bureau's data network, the emission inventory was generated according to Chinese national technical guidelines [50; 51] and relevant studies ([PERSON] et al., 2009 [52]; [PERSON] et al., 2015 [53]). Spatial allocation of emission inventory depended on the source characteristics. Haizhu district is an urban area, and the major emission sectors are industry, residential, and (road) transport. Emission sectors, corresponding inventory technical guidelines, and special allocation rules in this research are shown in Table S1.  
According to the 2015-based Haizhu district emission inventory, the 2020 Haizhu district emission inventory was predicted with the extrapolation function [13] [EI_2020 = \(f_{x}\) (EI_2015 \(\times\) activity factor), where EI refers to the emission inventory, and the activity factor refers to the trend of emission sections, gained from emission control policies for the 13 th Five-Year period [12; 49; 54] and the trend of city development in the past five to ten years (e.g., society, economy, vehicle and population, etc.) according to the statistical yearbook network ([[http://210.72.4.52/gzStatl/chaxun/njs.jsp](http://210.72.4.52/gzStatl/chaxun/njs.jsp)]([http://210.72.4.52/gzStatl/chaxun/njs.jsp](http://210.72.4.52/gzStatl/chaxun/njs.jsp)))). We note that the emission inventory in Haizhu district is compiled on an annual resolution. The resolution of these inventories was \(0.01^{\circ}\times 0.01^{\circ}\). All of the emission inventories have the same major sectors (transport, industry, and residential, etc.).