Wildfire Smoke Transport and Air Quality Impacts in Different Regions of China

atmosphere

Article Wildﬁre Smoke Transport and Air Quality Impacts in Diﬀerent Regions of China

Fengjun Zhao 1,2, Yongqiang Liu 2,*, Lifu Shu 1 and Qi Zhang 3

1 Research Institute of Forest Ecology, Environment and Protection, Forest Protection Laboratory of National Forestry and Grassland Administration, Chinese Academy of Forestry, Beijing 100091, China; [email protected] (F.Z.); [email protected] (L.S.) 2 Center for Forest Disturbance Science, USDA Forest Service, Athens, GA 30602, USA 3 Jiangsu Key Laboratory of Agricultural Meteorology, College of Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, China; [email protected] * Correspondence: [email protected]; Tel.: +1-706-559-4240

Received: 31 July 2020; Accepted: 30 August 2020; Published: 3 September 2020

Abstract: The air quality and human health impacts of wildfires depend on fire, meteorology, and demography. These properties vary substantially from one region to another in China. This study compared smoke from more than a dozen wildfires in Northeast, North, and Southwest China to understand the regional differences in smoke transport and the air quality and human health impacts. Smoke was simulated using the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) with fire emissions obtained from the Global Fire Emission Database (GFED). Although the simulated PM2.5 concentrations reached unhealthy or more severe levels at regional scale for some largest fires in Northeast China, smoke from only one fire was transported to densely populated 2 areas (population density greater than 100 people/km ). In comparison, the PM2.5 concentrations reached unhealthy level in local densely populated areas for a few fires in North and Southwest China, though they were very low at regional scale. Thus, individual fires with very large sizes in Northeast China had a large amount of emissions but with a small chance to affect air quality in densely populated areas, while those in North and Southwest China had a small amount of emissions but with a certain chance to affect local densely populated areas. The results suggest that the fire and air quality management should focus on the regional air quality and human health impacts of very large fires under southward/southeastward winds toward densely populated areas in Northeast China and local air pollution near fire sites in North and Southwest China.

Keywords: wildﬁre; PM2.5 emission; smoke modeling; HYSPLIT; local and regional impacts

1. Introduction Wildfires have increased in many regions of the world with a large number of devastating wildfires in recent years [1–7]. About two dozen extremely large fires occurred in the western United States in 2017 and 2018 with totally burned areas of about 22 thousand km2 (2.3 million hectares (hm2)). The 2018 Camp Fire in northern California damaged nearly 19 thousand structures and led to 85 deaths. The 2019–20 Australia bushfires burned 160 thousand km2 (16 million hm2) lands, leading to losses of over 3000 houses and 33 lives. The 2019 Amazon fires burned about 1500 km2 (150 thousand hm2) rainforest. The 2017 Portugal fires burned 5000 km2 (0.5 million hm2) with a loss of 119 human lives and the 2018 Greece Mati fires caused a loss of 99 people. In Russia, 25 thousand km2 (2.5 million hm2) were burned in 2019. Analyses and simulations have been conducted to understand fire occurrence and spread, weather and climate conditions, and the impacts of these fires.

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Forest fires are an important source of air pollutants. Fires occur and re-occur on almost a third of the global landmass at different return intervals, with burned areas averaging 4.5 million km2 annually [8,9]. Fires emit a large amount of gases including CO2, CO, CH4 and fine particular particles with a diameter of 2.5 micrometers or smaller (PM2.5). Although fine particles only account for 1.8% of flue gas [10], they can seriously affect air quality and human health [11–15]. Fine particles from fires not only affect local air quality, but also can be lifted to high altitudes by the heat of combustion and transported a long distance downwind to affect regional air quality and climate [16]. The contributions of fire emissions to air pollutants have been assessed in many regions of the world. For example, fires were found to contribute to about 30% of total PM2.5 emissions in the United States [17]. China is one of the most polluted countries in the world [18]. Average PM2.5 concentrations are over 50 µg/m3 in most of eastern China and even over 100 µg/m3 in some areas of this region [19]. Fine particles are also a key factor for the formation of regional haze and smog [20]. The severe pollutions cause premature deaths of more than one million people each year in China [21]. China has categorized local air pollution sources from automobile, industry, residence heating, and construction in major cities [22]. However, it is still not clear about the contributions from outside sources including wildfires [23]. The air quality and human health impacts of wildfires depend on many factors. Fire emission is a most important factor. Wildfires in China occur mainly in eastern China (approximately east of 110◦ E). Northeast and Southwest China are the two major fire regions with opposite contributions to the total number of fires and burned areas in China [24]. Northeast China has less than 5% of the total number of fires in China, but about 60% of the total burned areas; in contrast, Southwest China accounts for about 25% of the total number of fires, but only about 10% of the total burned areas [25]. Thus, it is expected that air pollutant emissions of individual fires are larger but occur less frequently in Northeast than in Southwest China. The contributions of fires in other regions to the total number of fires and burned areas in China are in between those in Northeast and Southwest China. Meteorological conditions are another important factor. Besides local temperature, humidity, wind, and precipitation that affect fire occurrence, spread, and smoke plume rise, large-scale circulations control long-distance transport of smoke [26]. All regions in China except the Northeast have a fire season mainly in spring. Although Northeast China has a fire season with two periods of spring and fall, fires in spring account for more than 70% of the total annual fires [25]. Thus, atmospheric circulations in spring are critical for smoke transport. Eastern China is mainly under the control of the winter phase of the East Asian monsoon [27] during the spring. The prevailing circulation system during this season is westerly in the mid-latitudes with dominant airflows from west to east. Demography is another factor for the air quality and human health impacts of wildfire smoke. The smoke exposure rate is closely related to population density. The rural population density is mostly between 10 and 100/km2 in eastern China, about 100–400/km2 in about one third of this region, including southern Northeast China, southeastern North China, and northeastern Southwest China [28]. The location of populated areas relative to the fire sites are critical to smoke exposure. Fires in Northeast China occur mainly in the Daxing’anling Mountains by the China-Russia border in far northwest of this region. The highly populated areas are located south of the fire sites and therefore not downwind of the prevailing westerly winds. In contrast, fires in the Southwest occur mostly in the western mountains with highly populated areas located downwind of the prevailing westerly winds. The locations of highly populated areas in North China are similar to those in Southwest China. Wildfire research in China has focused on fire ecology, fire-climate relationships, and fire prevention and suppression [29,30]. There have been increasing research efforts in fire emissions [31,32]. However, the studies on smoke transport and the air quality impacts are largely absent. This study investigated this issue with a focus on the regional differences. A hypothesis for this study was that individual fires in Northeast China have had large emission but small chance to affect air quality in highly populated areas, but an opposite situation might have happened for fires in Southwest and North Atmosphere 2020, 11, x FOR PEER REVIEW 3 of 23

2. Methodology

2.1. Study Area The study area was in eastern China, which was divided into five regions (Figure 1). The fire cases investigated in this study were from the Northeast, North, and Southwest China regions. China has aAtmosphere three-step2020 ,topography11, 941 with generally increasing elevations from east to west (Figure3 of1a). 24 The step 1 topography consists of the coastal plains and hills mostly below 500 m. The step 2 topography consists of the mountain ranges up to 3000 m (expect a lower area called the Sichuan Basin in northern SouthwestChina. China). This study The is step expected 3 topography to be valuable consists for evaluating of the Tibet the contributionsPlateau of 3000–6000 of wildfires m to and air the pollutions and improving fire and air quality management in China. northwestern deserts and mountains of 1000–3000 m. The eastern Northeast and North China are within2. Methodologythe step 1 topography; the Southwest, western Northeast, and western North China are within the step 2 topography, where a majority of lands are covered by needle and broad leaf trees (Figure 1b). 2.1.The Studypopulation Area density distributions described in the introduction section are illustrated in Figure 2a.The The study population area was indensity eastern was China, classified which was as divided sparsely into (<10 five people/km regions (Figure2), moderately1). The fire cases (10–100 people/kminvestigated2), and in thisdensely study were(>100 from people/km the Northeast,2) populated North, and in Southwestthis study. China The regions. three Chinaclassifications has a approximatelythree-step topography accounted with for generally60, 30, and increasing 10% areas elevations of the fromNortheast east to westregion, (Figure one1 a).third The each step 1of the Northtopography region, and consists 20, 60, of and the 20% coastal of the plains Southwest and hills region. mostly below 500 m. The step 2 topography consistsNortheast, of theNorth, mountain and Southwest ranges up China to 3000 are m unde (expectr the a control lower area of the called East the Asian Sichuan monsoon, Basin inwhich northern Southwest China). The step 3 topography consists of the Tibet Plateau of 3000–6000 m is extremely wet and warm during the summer phase and dry and cold during the winter phase. and the northwestern deserts and mountains of 1000–3000 m. The eastern Northeast and North Southwest China is also affected by the South Asian monsoon, which includes wet and dry phases. China are within the step 1 topography; the Southwest, western Northeast, and western North FiresChina in the are three within regions the step occurred 2 topography, mainly where during a majority the East of landsAsian are winter/S coveredouth by needle Asia anddry broadmonsoon phase.leaf The trees spring (Figure 5001b). hPa The geopotential population density height distributions (Figure 2b) described shows the in thewesterly introduction zone sectionnorth of are about 25° Nillustrated with a intrough Figure 2locateda. The population east of China density and was classifieda ridge asover sparsely western ( <10 China people /kmand2), Mongolia. moderately The corresponding(10–100 people prevailing/km2), and airflows densely (>over100 peoplethe Northeast,/km2) populated North, in thisand study. Southwest The three China classifications are mainly westerlyapproximately (i.e., eastward), accounted as forindicated 60, 30, and by 10%the areasarrows. of the The Northeast ground region, airflows one are third more each complex of the North due to the impactsregion, and of topography 20, 60, and 20% and of weather the Southwest systems region. such as fronts.

(a)

Figure 1. Cont.

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(b) (b)

FigureFigure 1. 1.Elevation Elevation ((aa)) andand landland covercover ((bb)) inin ChinaChina withwith geographicgeographic regionsregions inin easterneastern ChinaChina andand ﬁrefire Figure 1. Elevation (a) and land cover (b) in China with geographic regions in eastern China and fire locationslocations (The (The data data used used to to produce produce this this ﬁgure figure were were from from [ 33[33]).]). locations (The data used to produce this figure were from [33]).

(a) (a) Figure 2. Cont.

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(b)

FigureFigure 2.2.Population Population density density (a )(a (from) (from [28 [28])]) and and atmospheric atmospheric circulation circulation in the in 500 the hPa 500 geopotential hPa geopotential height field;height (b )field; (drawn (b using) (drawn the data using from the the USdata National from Centersthe US for National Environmental Centers Prediction for Environmental/Department ofPrediction/Department Energy Reanalysis-2 [34 of]). Energy Reanalysis-2 [34]).)

2.2. FireNortheast, Cases North, and Southwest China are under the control of the East Asian monsoon, which is extremely wet and warm during the summer phase and dry and cold during the winter phase. A total of 16 fires were investigated, seven from the Northeast, six from the North, and three Southwest China is also affected by the South Asian monsoon, which includes wet and dry phases. from the Southwest region (Figure 1 and Table 1). Four fires each in the Northeast and North regions Fires in the three regions occurred mainly during the East Asian winter/South Asia dry monsoon phase. occurred in the step 1 topography and the rest of the fires occurred in the step 2 topography. Thirteen The spring 500 hPa geopotential height (Figure2b) shows the westerly zone north of about 25 ◦ N with fires occurred in spring, two in fall, and one in summer. The burned areas in the Northeast region a trough located east of China and a ridge over western China and Mongolia. The corresponding were over 1000 km2 (100 k hm2) for three fires, 100–1000 km2 (10–100 k hm2) for two fires, and 50–100 prevailing airflows over the Northeast, North, and Southwest China are mainly westerly (i.e., eastward), km2 (5–10 k hm2) for two fires. The durations were longer than a week for five fires and four days for as indicated by the arrows. The ground airflows are more complex due to the impacts of topography two fires. The fires in the North and Southwest regions had burned areas of over 10 km2 (1 k hm2) for and weather systems such as fronts. four fires and 1–10 km2 (0.1–1 k hm2) for five fires. The durations were longer than a week for two 2.2.fires Fire and Cases 2–6 days for seven fires. The annual fire numbers during 1999–2017 were about 350, 230, 1850, and 7080 in the Northeast, North, and Southwest regions and in entire China based on the data A total of 16 fires were investigated, seven from the Northeast, six from the North, and three from the China National Forestry and Grassland Administration’s China National Forest Fire from the Southwest region (Figure1 and Table1). Four fires each in the Northeast and North regions Statistical System [35]. The corresponding burned areas were about 1190, 210, 240, and 2110 km2 (119, occurred in the step 1 topography and the rest of the fires occurred in the step 2 topography. Thirteen 21, 24, and 211 k hm2). The averaging burned areas were about 3.5, 0.9, 0.13, and 0.3 km2 (350, 90, 13, fires occurred in spring, two in fall, and one in summer. The burned areas in the Northeast region were and 30 hm2) each fire. The examples from the Northeast region were much larger than the averaging over 1000 km2 (100 k hm2) for three fires, 100–1000 km2 (10–100 k hm2) for two fires, and 50–100 km2 size. The examples from the North and Southwest regions were also larger than their averaging sizes. (5–10 k hm2) for two fires. The durations were longer than a week for five fires and four days for Fire boundaries, which were not available from the fire information provided by the fire two fires. The fires in the North and Southwest regions had burned areas of over 10 km2 (1 k hm2) management agency of China, were obtained from the Fire Information for Resource Management for four fires and 1–10 km2 (0.1–1 k hm2) for five fires. The durations were longer than a week for System (FIRMS) [36]. The FIRMS products had a resolution of 0.25° (approximately 25 km), obtained two fires and 2–6 days for seven fires. The annual fire numbers during 1999–2017 were about 350, based on the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Visible Infrared 230, 1850, and 7080 in the Northeast, North, and Southwest regions and in entire China based on Imaging Radiometer Suite (VIIRS) satellite remote sensing detection. The latitude and longitude the data from the China National Forestry and Grassland Administration’s China National Forest Fire ranges of a fire were determined based on the latitude and longitude values of the fire and the FIRMS Statistical System [35]. The corresponding burned areas were about 1190, 210, 240, and 2110 km2 (119, boundaries. 21, 24, and 211 k hm2). The averaging burned areas were about 3.5, 0.9, 0.13, and 0.3 km2 (350, 90, 13, and 30 hm2) each fire. The examples from the Northeast region were much larger than the averaging size. The examples from the North and Southwest regions were also larger than their averaging sizes.

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Table 1. Fire cases for smoke modeling.

Location Region No. Name Period Burned Area (km2) GFED Fuel Type Lon(◦ E) Lat(◦ N) 1 Shibazhan 125.78 52.10 5/17–26, 2003 3192.53 Boreal forest 2 Wuerqihan 122.66 49.54 5/25–6/1, 2006 299.56 Boreal forest 3 Huzhong 122.83 51.41 6/26–7/3, 2010 95.75 Boreal forest Northeast 4 Yichun 129.81 49.26 10/3–6, 2007 175.70 Boreal forest 5 Huma 126.55 51.13 10/23–30, 2005 1087.30 Boreal forest 6 Songling 124.63 50.88 5/22–6/2, 2006 2211.29 Boreal forest 7 Yimuhe 120.49 53.03 5/31–6/3, 2006 60.06 Boreal forest 8 Baoding 114.39 39.30 4/6–8, 2014 4.50 Temperate forest 9 Yangquan 113.46 37.90 4/29–5/1, 2011 22.49 Temperate forest 10 Weihai 122.12 37.49 5/29–31, 2014 1.20 Temperate forest North 11 Funing 119.63 40.13 4/12–18, 2011 10.67 Temperate forest 12 Laiwu 117.93 36.62 4/16–19, 2011 3.08 Temperate forest 13 Jinan 116.19 35.98 4/18–20, 2011 4.58 Temperate forest 14 Chuxiong 102.04 25.22 4/23–28, 2013 10.13 Temperate forest Southwest 15 Anning 102.68 25.06 3/29–4/7, 2006 18.49 Temperate forest 16 Dali 100.32 25.70 3/8–9, 2007 2.52 Temperate forest

Fire boundaries, which were not available from the fire information provided by the fire management agency of China, were obtained from the Fire Information for Resource Management System (FIRMS) [36]. The FIRMS products had a resolution of 0.25◦ (approximately 25 km), obtained based on the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Visible Infrared Imaging Radiometer Suite (VIIRS) satellite remote sensing detection. The latitude and longitude ranges of a fire were determined based on the latitude and longitude values of the fire and the FIRMS boundaries.

2.3. Smoke Modeling The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model [37] was used to simulate smoke transport and dispersion. HYSPLIT is a complete system for computing simple air parcel trajectories and complex dispersion and deposition. This model uses a hybrid modeling approach of either puffs, particles, or a combination of the two. In the particle model, which was used in this study, a fixed number of initial particles are advected over the model domain by the combined mean and turbulent wind fields. The mean wind fields are the wind field values at the grid points of the input meteorological data. The turbulent wind fields are calculated by HYSPLIT based on the vertical shear of the mean wind fields, atmospheric stability calculated based on temperature, and ground surface roughness which is mainly determined by vegetation type. The plume rise (that is, the height of the smoke plume) is calculated by the model based on the PM2.5 emissions and heat release. HYSPLIT uses a simple plume rise algorithm [38] originally developed for power plant stacks. Applications of more complex plume rise algorithms for wildfires [39,40] would possibly improve the smoke transport and the air quality modeling but were not used in this study. The heat release of fire missions was calculated using the scheme described in the Fire Emission Production Simulator (FEPS) [41]. HYSPLIT has been widely used for fire smoke modeling [42–44]. It was used in our recent smoke modeling study of the 2016 Rough Ridge Fire in northern Georgia, USA [45]. The location and size of the simulation domain varied with fire cases. The domain size in the zonal direction (west-east) or the meridional direction (south-north) ranged 10–40 degrees (approximately 1000–4000 km). A resolution of 0.25◦ (approximately 25 km) and 23 vertical levels (6 in the atmospheric boundary layer up to about 1.5 km above ground level) were used. The option of varied integration time step automatically set each hour by HYSPLIT was selected with the stability ratio of 0.75. The major simulation inputs included fire emissions and meteorology. The fire emissions were obtained from Atmosphere 2020, 11, 941 7 of 24 the gridded Global Fire Emissions Database, version 4 (GFED4) [8], which included small fires [46]. The GFED database was developed based on MODIS products. The resolution was 0.25◦ (approximately 25 km) with a daily time frequency. There were 32 species and products of fire emissions, including PM2.5, CO2, CO, NOx, and SO2. The simulations included no lateral chemical boundary transport. An evaluation study of burned areas in Daxing’anling showed good agreement in spring but poor in fall between the ground reported and the GFED data [47]. Calculations of fire emissions based on ground reported fire information and measured fuel conditions could improve smoke simulations from fires, especially those occurring in the fall. This approach was not used for this study. The meteorological variables were from the US National Oceanic and Atmospheric Administration (NOAA) reanalysis with a resolution of 2.5◦ (approximately 250 km, available until 2007) and the NOAA National Centers for Environmental Prediction (NCEP) Global Data Assimilation System (GDAS) with a resolution of 1◦ (approximately 100 km, available from 2005). HYSPLIT includes algorithms to interpolate meteorological fields at modeling grids (including those at lateral boundaries). Meteorological modeling using mesoscale models for the smoke modeling domains would provide high-resolution variables and improve smoke modeling. This approach was not used for this study. The US Environmental Protection Agency (EPA) Air Quality Index (AQI) color codes [48] were used to assess the human health impacts of smoke. The PM2.5 concentration ranges for the codes are as follows. Green (good AQI): 12 µg/m3; Yellow (moderate): 12.1–35.4 µg/m3; Orange (unhealthy ≤ for sensitive groups): 35.5–55.4 µg/m3; Red (unhealthy): 55.5–150.4 µg/m3; Brown (very unhealthy): 150.5–250.4 µg/m3; Purple (hazardous): 250.5 µg/m3. ≥ The air quality impacts of smoke were evaluated at local and regional scales based on simulated PM2.5 spatial distributions. The size to separate local and regional impacts is indeterminate, but the size of a region usually incorporates one or more cities, and is on the order of 100 to 10,000 km2 according to the American Meteorological Society (AMS) [49]. Because fire emissions are an elevated source, which is usually transported much longer in distance than the air pollutants emitted from the surface sources, we used 10,000 km2 (100 km in distance or about 4 grid points) to separate local and regional scales. The PM2.5 measurements from [50] were used for model evaluation.

3. Results

3.1. Fire Cases in Northeast China The seven fire cases were classified into three types according to their smoke transport direction and the air quality impacts. (1) Case 1: Smoke was transported from the fire site to densely populated areas in Northeast China with a potentially large human health impact; (2) Case 2: Same as Case 1 except with a potentially small human health impact. (3) Cases 3–7: Smoke was transported to Russia without impacts on densely populated areas in Northeast China. The Shibazhan fire occurred during 18–27 May 2003 in Daxing’anling near the China-Russia border (Figure3). Smoke was transported eastward about 500 km into the Russian territory on 3 23 May (Figure3a). The PM 2.5 concentrations were above 250 µg/m (hazardous level) in most areas of the smoke plume. Two days later, the direction of smoke transport turned to southeast (Figure3b). The smoke plume spread over eastern Heilongjiang Province of China. The PM2.5 concentrations remained above 250 µg/m3 in the first about 500 km downwind from the fire site with the areas sparsely populated (Figure2a). The PM 2.5 concentrations were reduced rapidly thereafter. However, there were 3 still many places with PM2.5 concentrations between 35 and 250 µg/m . The unhealthy conditions due to smoke affected the densely populated areas, including the cities of Mudanjiang and Jiamusi, both with populations of over 2 million. The smoke distributions remained less changed in the next four days (Figure3c,d) except that the smoke plume spread further southeastward as far as about 2000 km from the fire site. Atmosphere 2020,, 11,, x 941 FOR PEER REVIEW 8 8of of 23 24

FigureFigure 3. SimulatedSimulated smoke smoke plume plume from from th thee Shibazhan Shibazhan fire. ﬁre. Each Each square square box box is is a a model model grid grid point (approximately(approximately 25 25 km km × 2525 km). km). The The names names in black in black are areprovinces. provinces. The green, The green, yellow, yellow, orange, orange, red, × brown,red, brown, and purple and purple colors colors represen representt good, good, moderate, moderate, unhealthy unhealthy for sensitive for sensitive groups, groups, unhealthy, unhealthy, very unhealthy,very unhealthy, and hazardous and hazardous air qualit air qualityy levels, levels, respectively. respectively. Panels Panels (a–d) (area–d 18,) are 21, 18, 24, 21, and 24, 27 and May 27 2003, May respectively.2003, respectively.

TheThe Wuerqihan firefire occurred occurred during during 24 24 May–1 May–1 June Ju 2006ne 2006 in northern in northern Heilongjiang Heilongjiang Province, Province, about about500 km 500 southwest km southwest of case of 1 (Figurecase 1 (Figure4). Smoke 4). wasSmoke transported was transported eastward, eastward, traveling traveling more than more 1000 than km 3 1000into thekm Russiainto the territory Russia territory on May 24thon May (Figure 24th4 (Figurea). The 4a). PM The2.5 concentrations PM2.5 concentrations reached reached 55–150 55–150µg/m µg/m(unhealthy3 (unhealthy level) inlevel) a sparsely in a sparsely populated populated area a area few hundreda few hundred kilometers kilometers from thefrom fire the site. fire Thus, site. Thus,the human the human health health impacts impacts should should have been have minimal. been minimal. In addition In addition to eastward to eastward direction, direction, the smoke the smokewas transported was transported northward. northward. It was alsoIt was dispersed also disper southwardsed southward over the over entire the areaentire of area Northeast of Northeast China Chinaduring during the rest the of therest fire of periodthe fire (Figure period4 b–d).(Figure Despite 4b–d). densely Despite populated densely populated with many with cities, many the human cities, the human health should have been minimal due to the small PM2.5 concentrations of less than 12 µg/m3 (good air quality level).

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3 health should have been minimal due to the small PM2.5 concentrations of less than 12 µg/m (good air Atmosphere 2020, 11, x FOR PEER REVIEW 9 of 23 quality level).

FigureFigure 4.4. Same as Figure 33 exceptexcept forfor thethe WuerqihanWuerqihan ﬁre.fire. Panels (aa––dd)) are are 26, 26, 28, 28, 31 31 May May and and 2 2 June June 2006,2006, respectively.respectively.

TwoTwo ofof the the five five cases cases are are illustrated illustrated here here for thefor thirdthe third type type of fires. of fires. They They were diwerefferent different in fire seasonin fire andseason smoke and transport smoke transport direction. direct The Huzhongion. The fireHuzhong occurred fire from occurred 26 June from to 3 July26 June 2010, to in 3 Daxing’anling July 2010, in (FigureDaxing’anling5). The (Figure fire site 5). was The located fire site west was of located the first west fire of case. the first Smoke fire wascase. transportedSmoke was northwardtransported 3 acrossnorthward the China-Russia across the China-Russia border on 27border June (Figureon 27 June5a). (Figure The PM 5a).2.5 concentrationsThe PM2.5 concentrations reached 35 reachedµg/m (unhealthy35 µg/m3 (unhealthy to sensitive to groups) sensitive locally groups) and inlocally Russia. and The in smokeRussia. wasThe transportedsmoke was continuously transported northwardcontinuously and northward northwestward and northwestward deep into Russia deep on into 29 June Russia (Figure on 529b). June The (Figure PM 2.5 concentrations5b). The PM2.5 increasedconcentrations to more increased than 250 toµ gmore/m3 (hazardous) than 250 µg/m inside3 (hazardous) the border and inside 55–150 the µborderg/m3 (unhealthy) and 55–150 outside µg/m3 the(unhealthy) border. Smoke outside transport the border. remained Smoke this transport way until remained July 3rd this (Figure way 5untilc,d) July inside 3rd the (Figure border 5c,d) with inside very highthe border PM2.5 concentrations.with very high InPM addition,2.5 concentrations. there was In smoke addition, plume there development was smoke toward plume south development on 3 July. Thetoward human south health on 3 impactsJuly. The should human have health been impacts minimal should in these have sparsely been minimal populated in areastheseon sparsely 3 July whenpopulated the unhealthy areas on 3 portion July when of smoke the unhealthy did not goportion south of enough smoke todid reach not go the south moderately enough and to reach densely the populatedmoderately areas. and densely populated areas.

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FigureFigure 5.5. SameSame as Figure3 3 except except forfor thethe HuzhongHuzhong ﬁre.fire. Panels (aa––dd)) are are 27 27 and and 29 29 June June and and 1 1and and 3 3 JulyJuly 2010,2010, respectively.respectively.

TheThe YichunYichun firefire occurredoccurred duringduring aa fallfall periodperiod ofof 3–73–7 OctoberOctober 20072007 inin HeilongjiangHeilongjiang ProvinceProvince byby thethe China-RussiaChina-Russia borderborder (Figure(Figure6 6).). Smoke Smoke was was transported transported eastward eastward and and northeastward northeastward into into Russia Russia withwith smallsmall PMPM2.52.5 concentrations (good air quality) on 4 October (Figure(Figure6 6a).a). ItIt appearedappeared thatthat the the fire fire intensifiedintensified andand spreadspread towardtoward thethe southsouth onon thethe nextnext dayday leadingleading toto aa lineline ofof densedense smokesmoke longerlonger thanthan 500500 kmkm (Figure(Figure6 b)6b) with with sparsely sparsely and and moderately moderately populated populated areas. areas. The The PM PM2.52.5 concentrationsconcentrations werewere 3 overover 250250 µµg/mg/m 3 (hazardous).(hazardous). The smokesmoke waswas transportedtransported furtherfurther southsouth intointo RussiaRussia wherewhere the the PM PM2.52.5 3 concentrationsconcentrations werewere 55–15055–150 µµg/mg/m 3 inin thethe followingfollowing twotwo daysdays (Figure (Figure6 c,d).6c,d). Thus, Thus, the the high high PM PM2.52.5 concentrationsconcentrations shouldshould havehave hadhad aa moderatemoderate impactimpact onon humanhuman healthhealth inin somesome areas.areas. ForFor threethree otherother firesfires ofof thethe thirdthird typetype (illustrated(illustrated inin AppendixAppendixA A),), the the Huma Huma fire fire occurred occurred near near thethe YichunYichun firefire sitesite alsoalso duringduring thethe fallfall (24–31(24–31 OctoberOctober 2005)2005) (Figure(Figure A1 A1).). TheThe smokesmoke waswas transportedtransported 3 toto easteast andand southeast.southeast. TheThe PMPM2.52.5 concentrations of moremore thanthan 250250 µµg/mg/m 3 aaffectedffected somesome moderatelymoderately populatedpopulated areas.areas. The The Songling Songling fire fire occurred occurred in Daxing’anling, in Daxing’anling, northwest northwest of the of Yichun the Yichun fire site, fire during site, 22during May to22 2May June to 2006 2 June (Figure 2006 A2 (Figure). The smokeA2). The was smoke transported was transported to east, northeast, to east, andnortheast, north. and The PMnorth.2.5 3 concentrationsThe PM2.5 concentrations of more than of more 250 µ gthan/m 250affected µg/m sparsely3 affected populated sparsely populated areas. The areas. Yimuhe The fire Yimuhe occurred fire furtheroccurred west further during west 1–4 during June 20061–4 June (Figure 2006 A3 (Figure). The smokeA3). The was smoke transported was transported north with north minimal with healthminimal impacts. health impacts.

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FigureFigure 6. 6. SameSame as as FigureFigure3 except3 except for thefor Yichunthe Yichun fire. Panels fire. (Panelsa–d) are ( 4,a– 5,d) 6, are and 4, 7 October5, 6, and 2007, 7 October respectively. 2007, respectively. 3.2. Fire Cases in North China 3.2. FireThe Cases fires in andNorth smoke China transport were classified into two types. (1) Cases 8–10: Fires with smoke transported mainly in one direction; (2) Cases 11–13: Fires with smoke transported in two or The fires and smoke transport were classified into two types. (1) Cases 8–10: Fires with smoke more directions. transported mainly in one direction; (2) Cases 11–13: Fires with smoke transported in two or more The Baoding fire occurred during 6–8 April 2014 in Hebei Province, about 500 km southwest of directions. Beijing, the nation’s capital (Figure7). Smoke was transported eastward on 7 April reaching south of The Baoding fire occurred during 6–8 April 2014 in Hebei Province,3 about 500 km southwest of Beijing (Figure7a). The PM 2.5 concentrations were small, about 12 µg/m at the fire site and another Beijing, the nation’s capital (Figure 7). Smoke was transported eastward on 7 April reaching south of spot about 100 km away in the northeast. Smoke continued to move east the next day with PM2.5 3 Beijingconcentrations (Figure 7a). increased The PM to2.5 55–150 concentrationsµg/m3 (Figure were7b) small, in a local about area 12 of µg/m denselyat the populated fire site (Figure and another7b). spotThus, about the 100 smoke km ledaway to unhealthyin the northeast. air quality Smoke mainly continued near the to fire move site, whicheast the should next haveday with affected PM2.5 3 concentrationshuman health. increased The measurements to 55–150 µg/m of PM2.5 (Figurewere available7b) in a local for this area fire of casedensely (Figure populated8). The measured (Figure 7b). Thus,values the were smoke stable led atto aboutunhealthy 40 µg air/m3 qualityduring mainly the three near days the prior fire tosite, the which Baoding should fire. have The valuesaffected humanincreased health. to about The measurements 65, 93, and 151 µofg /PMm3 2.5on were the three available days offor the this fire fire period. case (Figure The contributions 8). The measured from valuesthe fire were (excluding stable at the about background 40 µg/m concentrations)3 during the werethree aboutdays 50priorµg/ mto3 onthe 7 Baoding April and fire. 110 µTheg/m values3 on increased8 April. to Thus, about the 65, simulated 93, and PM1512.5 µg/mconcentrations3 on the three were days comparable of the fire to period. the measured The contributions magnitude onfrom the8 fire April (excluding but slightly the underestimated background concentrations) on 7 April. were about 50 µg/m3 on 7 April and 110 µg/m3 on 8 April. Thus, the simulated PM2.5 concentrations were comparable to the measured magnitude on 8 April but slightly underestimated on 7 April. The Yangquan fire occurred during 29 April–1 May 2011, in Shanxi Province (Figure A4). Smoke was transported mainly southeastward, reaching the southeastern coast about 1500 km away. The Weihai fire occurred during 30–31 May 2014, in the coastal area of Shandong Province (Figure A5). Smoke was transported northeastward. The PM2.5 concentrations from either fire were smaller than 35 µg/m3.

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Figure 7. SameSame as as Figure Figure 33 except for the Baoding ﬁre.fire. Panels (aa––bb)) are are 7 7 and and 8 8 April April 2014, 2014, respectively. respectively.

160 151 140

120

100

80 PM2.5 PM2.5 60

3 FigureFigure 8.8. Measured PMPM2.52.5 concentrationsconcentrations (µg/m (µg/m )) in in Baoding. Baoding.

The Funing Yangquan fire fireoccurred occurred from during 12 to 18 29 April April–1 2011 May in Hebei 2011, Province, in Shanxi less Province than 500 (Figure km east A4 of). SmokeBeijing was(Figure transported 9). On 14 mainlyand 15 April, southeastward, smoke was reaching transported the southeastern northeastward coast to Northeast about 1500 China km away. and Theeastward Weihai to firethe occurredsea area (Figure during 9a,b). 30–31 The May smoke 2014, incontinued the coastal to move area of this Shandong way the Province following (Figure two days, A5). Smokebut in the was meantime, transported smoke northeastward. was also transported The PM2.5 southwardconcentrations to South from China either (Figure fire were 9c,d). smaller The PM than2.5 3 35concentrationsµg/m . were smaller than 12 µg/m3 during the entire fire period. Thus, smoke from this fire spreadThe over Funing densely fire populated occurred from areas 12 but to 18should April not 2011 have in Hebeihad much Province, impact less on thanhuman 500 health. km east The of Beijingsmoke from (Figure either9). On the 14 Laiwu and 15fire April, occurring smoke during was transported 17–19 April northeastward 2011 (Figure A6) to Northeast or the Jinan China fire andoccurring eastward during to the18–20 sea April area (Figure2011 (Figure9a,b). A7) The in smoke Shandong continued Province to move was thissimilar way to the that following from the twoFuning days, fire, but but in spread the meantime, in two directions smoke was of alsonortheast transported and south southward only over to Souththe land China areas. (Figure 9c,d). 3 The PM2.5 concentrations were smaller than 12 µg/m during the entire fire period. Thus, smoke from this fire spread over densely populated areas but should not have had much impact on human health. The smoke from either the Laiwu fire occurring during 17–19 April 2011 (Figure A6) or the Jinan fire occurring during 18–20 April 2011 (Figure A7) in Shandong Province was similar to that from the Funing fire, but spread in two directions of northeast and south only over the land areas.

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Figure 9. Same as Figure3 except for the Funing fire. Panels (a–d) are 14, 15, 16, and 17 April 2011, respectively. Figure 9. Same as Figure 3 except for the Funing fire. Panels (a–d) are 14, 15, 16, and 17 April 2011, 3.3. Firerespectively. Cases in Southwest China The Chuxiong fire (case 14) occurred during 23–28 April 2013 in Yunnan Province (Figure 10). Smoke3.3. Fire wasCases transported in Southwest eastward China to form a smoke line of over 1000 km long from central Yunnan ProvinceThe Chuxiong to eastern fire Guizhou (case 14) Province occurred on during 24 April 23–28 (Figure April 102013a). in The Yunnan PM2.5 Provinceconcentration (Figure was10). 3 35–55Smokeµ gwas/m transportednear the fire eastward site. It aff ectedto form Kunming, a smoke the line province of over capital 1000 km with lo ang population from central of 6Yunnan million people.Province The to concentrationseastern Guizhou were Province very small on 24 in April other (Figure areas. The 10a). smoke The PM started2.5 concentration to dispersesouthward was 35–55 onµg/m 263 Aprilnear the reaching fire site. the It coastal affected area Kunming, of Guangxi the (Figureprovince 10 capitalb). In thewith following a population days, of the 6 million smoke furtherpeople. spreadThe concentrations toward the eastwere and very north. small The in othe PMr2.5 areas.concentrations The smoke remained started to smalldisperse (Figure southward 10c,d). Theon 26 transport April reaching of smoke the fromcoastal two area other of Guangxi fires (cases (Figure 15–16) 10b). in In Southwest the following China days, was the similar smoke to further that of 3 thespread Chuxioang toward firethe except east and that north. the PM The2.5 concentrations PM2.5 concentrations from the remained Dali fire were small smaller (Figure than 10c,d). 12 µg The/m (Figurestransport A8 of andsmoke A9 ).from two other fires (cases 15–16) in Southwest China was similar to that of the Chuxioang fire except that the PM2.5 concentrations from the Dali fire were smaller than 12 3.4. Discussion µg/m3(Figures A8 and A9). The simulation results of the16 fire cases summarized in Table2 indicate that the investigated fires in the Northeast region occurred in the remote mountains north of the densely populated areas. The PM2.5 concentrations reached the hazardous level for most cases. However, smoke was transported to the sparsely populated areas for a majority of fire cases. Smoke affected densely populated areas only for one fire case and moderately populated areas for two fire cases. The locations and impacts of the fires in this region were similar to those in the Rocky Mountains of the United States.

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Figure 10. Same as Figure3 except for the Chuxiong fire. Panels ( a–d) are 26–29 April 2013, respectively. FigureTable 10. Same 2. Smoke as Figure transport 3 except and air for quality the impacts.Chuxiong S and fire. Rus Panels in parenthesis (a–d) are represent 26, 27,28, sensitive and 29 groups April 2013, respectively.and Russia, respectively. The population density is the population density classiﬁcation of the areas in China where smoke PM2.5 concentrations reached the level of unhealthy to sensitive groups or worse.

3.4. Discussion Air Quality Impact Reg No. Name Site Relative to Cities Transport Direction Population Density Local Regional The simulation1 results Shibazhan of the16 north fire cases southeastsummarized hazardous in Table 2 hazardousindicate that the dense investigated fires in the Northeast2 Wuerqihanregion occurrednorth in the remo East, northte mountains unhealthy north of the good densely populated sparse areas. 3 Huzhong north mainly north hazardous unhealthy (Rus) sparse The PMNortheast2.5 concentrations4 Yichun reached north the hazardous east, south level hazardousfor most unhealthycases. (Rus) However, moderate smoke was transported to the5 sparsely Huma populated north areas east,for southeast a majority hazardous of fire hazardouscases. (Rus)Smoke affected moderate densely populated areas 6only Songling for one fire north case and north, mode northeastrately hazardouspopulated hazardousareas (Rus) for two sparsefire cases. The 7 Yimuhe north north very unhealthy very unhealthy (Rus) sparse locations and impacts8 Baodingof the fires in west this region were east similar unhealthy to those in moderate the Rocky Mountains dense of the United States. 9 Yangquan west southeast good good dense * 10 Weihai east northeast moderate moderate dense * North In contrast, smoke11 Funing from all surroundingnine fires in North east, south and Southwest good China good was transported dense * to densely populated areas.12 However, Laiwu the surrounding PM2.5 concentrations northeast, south reached good the leve goodl of unhealthy dense *to sensitive groups only in local13 areas Jinan for three surrounding fire cases. Th northeast,us, souththe regional good air quality good and human dense health * impacts 14 Chuxiong west east unhealthy (S) good dense of theseSouthwest fires were15 minimal. Anning One west reason for the northeast minimal unhealthy regional (S) impacts good was that dense the Chinese government had 16implemented Dali a strict west forest fire northeast suppression good policy since good the catastrophic dense * 1987 Black Dragon fires in Daxing’anling* The area where [51] smoke. A PMfire2.5 concentrationswould be suppressed were at either good asor soon moderate as possible. level. Once a fire was observed, theIn contrast, local government smoke from allwa nines notified ﬁres in Northimmediately, and Southwest and it China determined was transported the amount to densely of human resourcespopulated to deploy areas. to However, fight the the fire PM [52].2.5 concentrations As a result, reached most fires the level would of unhealthy grow slowly to sensitive and diminish groups in a period of a few days. Thus, burned areas and emissions of these fires were mostly small with only minimal impacts on air quality downwind. The evaluation of the modeling results suggested a difference in the contributions of fire smoke to regional air quality and human health between the China regions and some other fire regions in the world such as the United States. The PM2.5 concentrations from non-fire sources in Fig.8 was about 40 µg/m3. This value was comparable to the average values for the eastern China from a global analysis [19]. The concentrations in the continental US from the analysis were less than half of the

Atmosphere 2020, 11, 941 15 of 24 only in local areas for three fire cases. Thus, the regional air quality and human health impacts of these fires were minimal. One reason for the minimal regional impacts was that the Chinese government had implemented a strict forest fire suppression policy since the catastrophic 1987 Black Dragon fires in Daxing’anling [51]. A fire would be suppressed as soon as possible. Once a fire was observed, the local government was notified immediately, and it determined the amount of human resources to deploy to fight the fire [52]. As a result, most fires would grow slowly and diminish in a period of a few days. Thus, burned areas and emissions of these fires were mostly small with only minimal impacts on air quality downwind. The evaluation of the modeling results suggested a difference in the contributions of fire smoke to regional air quality and human health between the China regions and some other fire regions in the world such as the United States. The PM2.5 concentrations from non-fire sources in Figure8 was about 40 µg/m3. This value was comparable to the average values for the eastern China from a global analysis [19]. The concentrations in the continental US from the analysis were less than half of the values in China. The PM2.5 concentrations on 8 April 2014 from the Baoding fire were at the unhealthy level. With the background value, however, the total PM2.5 (measured) reached the very unhealthy level. Thus, although the PM2.5 concentrations from fires in the North or Southwest region of China usually were small, air pollutions could be still heavy during a smoke period because of the large background PM2.5 level. The impact of smoke from fires in Northeast China on air quality in Russia is a concern for the fire and air quality management in both China and Russia. A related issue is smoke transport into China from fires in Russia. The Euro-Asia boreal, mainly in Siberia, is one of the major wildfire regions in the world. The fire number, size, intensity, and duration in this region usually are much more than those in Northeast China. Smoke from the fires in Siberia can be transported a long distance to affect air quality in eastern Asia including China. For example, the smoke from the 2003 spring Siberia 3 fires was transported to Northeast and North China with PM2.5 concentrations exceeding 55 µg/m (unhealthy) [53]. Further research is needed to simulate the across-boundary smoke transport to improve the assessment of the contributions of wildfires to the air pollutions in China. One of the limitations with this study is that only a limited number of fire cases were simulated. Because the spatial extend and magnitude of exposures and resultant health outcomes depend on the location, timing and duration of wildfires as well the prevailing meteorological conditions, the results from this study only included certain spatial patterns and magnitude of smoke transport and impacts. The fire cases in the Northeast region simulated in this study included major largest fires in this region during recent two decades, including the fires during 2003 and 2006 when nearly 9000 km2 and 4700 km2 were burned, respectively, much more than other years during the two-decade period (Figure A10). Fires in the North and Southwest regions were usually much smaller than these in the Northeast region because of the moister conditions (especially in the Southwest region) and better accessibility for fire suppression due to closer fire sites to densely populated areas (especially in the North region). Also, fires usually occurred either in the mountains west of the downwind densely populated areas or within densely populated areas. Thus, it is expected that the simulation results of the fire cases investigated in this study, despite a small number, reflected some general spatial patterns and magnitude of smoke transport and impacts in the two regions.

4. Conclusions Smoke has been simulated for more than a dozen wildfires in the Northeast, North, and Southwest China. The regional differences in smoke transport and the air quality and human health impacts obtained from the modeling results provided evidence for the hypothesis for this study, that is, individual fires with very large sizes in Northeast China had a large amount of emissions but a small chance to affect air quality in densely populated areas, while fires in North and Southwest China usually had small emissions with large local impacts in some cases. This finding suggests that the fire Atmosphere 2020, 11, x FOR PEER REVIEW 16 of 23

4. Conclusions Smoke has been simulated for more than a dozen wildfires in the Northeast, North, and Southwest China. The regional differences in smoke transport and the air quality and human health impacts obtained from the modeling results provided evidence for the hypothesis for this study, that is, individual fires with very large sizes in Northeast China had a large amount of emissions but a small chance to affect air quality in densely populated areas, while fires in North and Southwest China usually had small emissions with large local impacts in some cases. This finding suggests that the fire and air quality management should focus on fires with very large sizes under wind directions toward the south in Northeast China and local air pollutions from fires in the North and Southwest China. Atmosphere 2020, 11, 941 16 of 24 Author Contributions: F.Z. led the development and implementation of the research project. F.Z. and Y.L. wrote the manuscript. L.S. and Q.Z. participated in discussion. All authors have read and agreed to the published and air quality management should focus on fires with very large sizes under wind directions toward version of the manuscript. the south in Northeast China and local air pollutions from fires in the North and Southwest China. Funding: China National Key Research and Development Plan (2017YFD0600106) and China Natural Science Author Contributions: F.Z. led the development and implementation of the research project. F.Z. and Y.L. wrote Foundationthe manuscript.under project L.S. (31670661). and Q.Z. participated in discussion. All authors have read and agreed to the published version of the manuscript. Acknowledgments: The authors would like to thank the three reviewers for valuable comments and Funding: China National Key Research and Development Plan (2017YFD0600106) and China Natural Science suggestions,Foundation Libo Zhang under project for help (31670661). in modeling, and Shela Mou for English editing. This study was supported by Chinese Acknowledgments:Academy of ForestryThe authors and wouldUSDA like Forest to thank Service. the three reviewersThe Global for valuable Fire Emission comments andDatabase, suggestions, the NOAA HYSPLITLibo model Zhang and for helpreanalysis in modeling, data andwere Shela used. Mou The for elev Englishation editing. and vegetation This study was type supported data were by Chinese obtained from GeospatialAcademy Information of Forestry Authority and USDA of Forest Japan. Service. The Global Fire Emission Database, the NOAA HYSPLIT model and reanalysis data were used. The elevation and vegetation type data were obtained from Geospatial Information ConflictsAuthority of Interest: of Japan. The authors declare no conflicts of interest. Conflicts of Interest: The authors declare no conflict of interest.

AppendixAppendix A A

Figure FigureA1. Simulated A1. Simulated smoke smoke plume plume from from the theHuma Huma fire. ﬁre. Each Each square square box box is is a model gridgrid point point (approximately 25 km 25 km). The names in black are provinces. The green, yellow, (approximately 25 km × 25 km). ×The names in black are provinces. The green, yellow, orange, red, orange, red, brown, and purple colors represent good, moderate, unhealthy for sensitive groups, brown, and purple colors represent good, moderate, unhealthy for sensitive groups, unhealthy, very unhealthy, very unhealthy, and hazardous air quality levels, respectively. Panels (a–d) are 25, 27, 29, unhealthy,and 31and October hazardous 2005, respectively. air quality levels, respectively. Panels (a–d) are 25, 27, 29, and 31 October 2005, respectively.

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FigureFigure A2. Same A2. Sameas Figure as Figure A1 except A1 except for the for theSongling Songling fire. ﬁre. Panels Panels (a (–ad–)d )are are 25, 25, 28, 28, and and 31 31 May May and 3 June 2006,and 3respectively. June 2006, respectively.

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Figure A3. Same as Figure A1 except for the Yimuhe fire. Panels (a–d) are 1, 2, 3, and 4 June 2006, respectively. FigureFigure A3. A3.SameSame as asFigure Figure A1 A1 exceptexcept for for the the Yimuhe Yimuhe fire. Panelsfire. Panels (a–d) are (a 1,–d 2,) 3,are and 1, 4 2, June 3, 2006,and 4 respectively. June 2006, respectively.

Figure A4. Same as Figure A1 except for the Yangquan ﬁre. Panels (a–c) are 30 April and 1 and 2 May 2011, respectively. Figure A4. Same as Figure A1 except for the Yangquan fire. Panels (a–c) are 30 April and 1 and 2 May 2011, respectively. Figure A4. Same as Figure A1 except for the Yangquan fire. Panels (a–c) are 30 April and 1 and 2 May 2011, respectively.

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Figure A5. Same as Figure A1 except for the Weihai fire. Panels (a,b) are 30 and 31 May 2014, respectively. Figure A5.A5. SameSame as as Figure Figure A1 A1except except for the for Weihai the Weihai ﬁre. Panels fire. (Panelsa,b) are ( 30a,b and) are 31 May30 and 2014, 31 respectively. May 2014, respectively.

Figure A6. Same asas Figure Figure A1 A1 except except for for the the Laiwu Laiwu fire. fire. Panels Panels (a–c) are(a–c 17,) are 18, 17, and 18, 19 Apriland 19 2011, April respectively. 2011, Figurerespectively. A6. Same as Figure A1 except for the Laiwu fire. Panels (a–c) are 17, 18, and 19 April 2011, respectively.

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Figure A7. Same as Figure A1 except for the Jinan fire. Panels (a–c) are 19, 20, and 21 April 2011, respectively. Figure A7. Same as Figure A1 except for the Jinan fire. Panels (a–c) are 19, 20, and 21 April 2011, respectively. Figure A7. Same as Figure A1 except for the Jinan fire. Panels (a–c) are 19, 20, and 21 April 2011, respectively.

Figure A8. A8. SameSame as asFigure Figure A1 A1 except except for the for Anning the Anning fire. Panels ﬁre. Panels (a–d) are (a– 30d) March are 30 and March 2, 5, and and 2,8 5, Apriland 8 2006, April respectively. 2006, respectively. Figure A8. Same as Figure A1 except for the Anning fire. Panels (a–d) are 30 March and 2, 5, and 8 April 2006, respectively.

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Figure A9. Same as Figure A1 except for the Dali fire on 8 March 2007. Figure A9. Same as Figure A1 except for the Dali ﬁre on 8 March 2007. Figure A9. Same as Figure A1 except for the Dali fire on 8 March 2007.

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