中国重要旅游城市雾霾时空特征

依托中国15个重要旅游城市，基于雾霾主导因素PM2.5观测数据、遥感气溶胶数据，运用土地利用回归方法模拟绘制PM2.5时空分布图，分析中国重要旅游城市PM2.5质量浓度的时空分异特征。结果表明：1）2013―2015年中国重要旅游城市PM2.5年均质量浓度总体呈逐年下降趋势，且明显呈现夏季低、冬季高、春秋季居中的季节变化特征；2）重要旅游城市PM2.5质量浓度在不同等级城市中存在明显差异，其PM2.5质量浓度整体规律为副省级市＞直辖市＞地级市；3）月均尺度上各重要旅游城市的宜游时间主要集中在4―9月，且2015年春冬季月份宜游城市明显增多；宜游时间较长的城市主要分布在空气质量优良的东南部沿海和森林覆盖率较高地区的地级市和部分副省级市，中西部地区和长三角地区的城市宜游时间则相对较短。

Spatial-temporal Characteristics of Haze in the Key Tourism Cities of China

Based on the discrete in situ PM2.5 observed data, AOD data, as well as the meteorological data, in this study the temporal-spatial distribution of PM2.5 concentration at monthly scale in fifteen key tourism cities of China for years 2013, 2014, 2015 was firstly simulated by using the land use regression (LUR) method. Then, the seasonal and annual PM2.5 concentrations across the entire study period were consequently produced based on these monthly PM2.5 distribution maps with the aid of spatial overlay and raster calculation techniques in ArcGIS tool. Finally, the spatial-temporal heterogeneity of PM2.5 concentrations at scales of monthly, seasonal and annual in each key tourism city were statistically analyzed. Generally, the annual average PM2.5 concentrations of the fifteen key tourism cities showed a gradually declining trend from 2013 to 2015 with significantly higher values in winter and lower values in summer. Spring and autumn were usually with annual average PM2.5 concentrations between those of winter and summer. Meanwhile, the declining trend of PM2.5 concentrations could also be clearly observed at seasonal and monthly scale except a little abnormal increase in the summer of 2014. Moreover, comparisons of the PM2.5 concentrations at the three time scales among the fifteen key tourism cities in this study revealed that the deputy provincial cities were usually with higher PM2.5 concentrations, while the prefecture level cities were with the lowest values, and the values for municipalities were in the middle. Additionally, as for the suitable time for traveling in terms of air quality , the months from April to November were the good time window for travel for the fifteen tourism cities, especially during the period from July to September. However, the suitable travel time window obviously increased in spring and winter of 2015 with the air quality improvement. Spatially, the deputy provincial cities and prefecture-level cities located in southeast coastal areas and high forest coverage rate areas usually had longer suitable travel time, such as Kunming, Sanya, Xiamen and Guangzhou. Inversely, the suitable travel time was relatively short in the central and western regions as well as the Yangtze River Delta region such as Wuhan, Chengdu and Shanghai. In sum, as the first quantitative analysis of the suitable travel time of tourism city in China with spatial mapping method, this study would provide helpful suggestions for tourist decision in choosing the suitable travel time for specific tourism city. And this would be a significant extension of current research fields of urban tourism, and would consequently promote researches on the influences of inner driving mechanism of haze pollution on urban tourism, as well as on the tourism product structure and tourism operation.