Stroh Emilie, Harrie Lars, Gustafsson Susanna
GIS Centre, Lund University, Sölvegatan 12, Lund, Sweden.
Int J Health Geogr. 2007 Jun 4;6:19. doi: 10.1186/1476-072X-6-19.
This study is part of several ongoing projects concerning epidemiological research into the effects on health of exposure to air pollutants in the region of Scania, southern Sweden. The aim is to investigate the optimal spatial resolution, with respect to temporal resolution, for a pollutant database of NOx-values which will be used mainly for epidemiological studies with durations of days, weeks or longer periods. The fact that a pollutant database has a fixed spatial resolution makes the choice critical for the future use of the database.
The results from the study showed that the accuracy between the modelled concentrations of the reference grid with high spatial resolution (100 m), denoted the fine grid, and the coarser grids (200, 400, 800 and 1600 meters) improved with increasing spatial resolution. When the pollutant values were aggregated in time (from hours to days and weeks) the disagreement between the fine grid and the coarser grids were significantly reduced. The results also illustrate a considerable difference in optimal spatial resolution depending on the characteristic of the study area (rural or urban areas). To estimate the accuracy of the modelled values comparison were made with measured NOx values. The mean difference between the modelled and the measured value were 0.6 mug/m3 and the standard deviation 5.9 mug/m3 for the daily difference.
The choice of spatial resolution should not considerably deteriorate the accuracy of the modelled NOx values. Considering the comparison between modelled and measured values we estimate that an error due to coarse resolution greater than 1 mug/m3 is inadvisable if a time resolution of one day is used. Based on the study of different spatial resolutions we conclude that for urban areas a spatial resolution of 200-400 m is suitable; and for rural areas the spatial resolution could be coarser (about 1600 m). This implies that we should develop a pollutant database that allows different spatial resolution for urban and rural areas.
本研究是瑞典南部斯堪尼亚地区几个正在进行的有关空气污染对健康影响的流行病学研究项目的一部分。目的是针对主要用于持续数天、数周或更长时间的流行病学研究的氮氧化物值污染物数据库，研究相对于时间分辨率的最佳空间分辨率。污染物数据库具有固定的空间分辨率这一事实使得该选择对于数据库的未来使用至关重要。
研究结果表明，具有高空间分辨率（100米）的参考网格（称为精细网格）与较粗网格（200、400、800和1600米）的模拟浓度之间的准确性随着空间分辨率的提高而提高。当污染物值按时间聚合（从小时到天和周）时，精细网格与较粗网格之间的差异显著减小。结果还表明，根据研究区域的特征（农村或城市地区），最佳空间分辨率存在相当大的差异。为了估计模拟值的准确性，将模拟值与实测氮氧化物值进行了比较。模拟值与测量值的日平均差异为0.6微克/立方米，标准差为5.9微克/立方米。
空间分辨率的选择不应显著降低模拟氮氧化物值的准确性。考虑到模拟值与测量值的比较，我们估计，如果使用一天的时间分辨率，粗分辨率导致的误差大于1微克/立方米是不可取的。基于对不同空间分辨率的研究，我们得出结论，对于城市地区，200 - 400米的空间分辨率是合适的；对于农村地区，空间分辨率可以更粗（约1600米）。这意味着我们应该开发一个允许城市和农村地区采用不同空间分辨率的污染物数据库。
