**4. Conclusions**

This study focused on the impacts of BB emission inventories and atmospheric reanalyses on the simulation of PM10 over Indochina for the year 2014. Meteorological fields to input to CMAQ were produced by using the WRF model simulation with NCEP FNL or ERA-interim. FINN v1.5 or GFED v4.1s were selected for BB emissions. In order to evaluate the impacts, four cases of simulations (FNL + FINN; FNL + GFED; ERA + FINN; ERA + GFED) were executed.

The performance of CMAQ simulations for PM10 concentrations at ground-level was evaluated at Bangkok and Chiang Mai in Thailand. The FNL + FINN case performed best for both the full year and the two-month period when BB activities were intensified in 2014. To compare the impacts of input data (BB emission inventories and atmospheric reanalyses) on simulated PM10, we introduced the normalized percentage difference for FNL + FINN and the other three cases (FNL + GFED; ERA + FINN; ERA + GFED) for annual mean and maximum daily mean PM10 concentrations in 2014 at the two observation sites. At both of the two sites, the normalized percentage difference for annual mean and maximum daily mean PM10 concentrations in 2014 for FNL + FINN and the two cases applying GFED v4.1s for BB emissions (FNL + GFED; ERA + GFED) was larger than that between FNL + FINN and ERA + FINN cases. In particular, the difference for maximum daily mean PM10 concentrations at Chiang Mai for FNL + FINN and the two cases applying GFED v4.1s (−53% to −27%) was much larger than that between the FNL + FINN and ERA + FINN cases (10%).

BB contributions were estimated by the difference between the cases with BB emissions and those without BB emissions. BB contributions to PM10 concentrations in the four simulation cases at Chiang Mai (75%–89%) were larger than those at Bangkok (2%–12%) on the day when the highest PM10 concentrations were observed in 2014 at each observation site. BB highly contributed on the particulate pollution over Southern china and Cambodia on January 3, and over the area along the Myanmar and Thailand border on March 21 in weak-wind condition. In polluted areas caused by BB, the cases applying FINN v1.5 for BB emission inventories showed higher trends of PM10 concentrations. Selected BB emission inventories more strongly impacted the PM10 simulation than selected atmospheric reanalyses in highly polluted areas by BB over Indochina in 2014.

This approach is applicable to other years and atmospheric pollutants to evaluate the impacts of selected input datasets on air quality simulations in polluted areas caused by BB. For example, GFAS can be used for one of the other BB emission inventories. However, emission factors of global BB emission inventories, such as FINN, GFAS, and GFED, were determined based on generic vegetation types of each fire pixel. BB-emission data focusing on the unique characteristics of BB in the specific region would reduce the uncertainties of BB emissions. We hope that this study will help to improve understanding about the mechanisms that degrade air quality over Indochina.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2073-4433/11/2/160/s1, Table S1. Model performance for daily mean meteorological factors in the two simulation cases for the periods of one year and two months (from March to April) in 2014. Table S2. Model performance for daily mean PM10 concentrations in the four simulation cases for the periods of one full year (2014) and two months (from March to April 2014).

**Author Contributions:** Conceptualization, K.T., H.S., and A.K.; methodology, H.S. and K.U.; software, H.S. and K.U.; validation, K.T. and H.S.; formal analysis, K.T. and H.S.; data curation, H.S.; writing—original draft preparation, K.T.; writing—review and editing, H.S., K.U., and A.K.; visualization, K.T.; supervision, A.K.; project administration, H.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
