基于AIS轨迹修复的船舶排放空间表征改进方法与应用

基于船舶自动识别系统（Automatic Identification System，AIS）数据表征船舶排放是目前船舶排放空间表征的主流方法，但AIS船舶轨迹点缺失会造成船舶排放量低估和船舶空间分布表征错误，进而影响船舶排放控制区的划分.为改进船舶排放空间表征，本研究以2013年广东省AIS船舶数据为例，采用基于时间和经纬度的三次样条方法对AIS船舶轨迹进行修复，结合动力法计算船舶排放，分析对比AIS轨迹修复前后船舶排放表征的差异，并利用空气质量模型和卫星观测评估AIS轨迹修复对船舶排放表征和广东沿海空气质量模拟的改进效果.结果表明：轨迹修复后广东省海域船舶轨迹点总数由4685773个增至5746664个，船舶NO_x排放量增加了0.6%.对于轨迹点与排放缺失集中的粤东海域，轨迹修复后船舶轨迹点数增加了88%，NO_x排放量在广东省船舶排放量的占比提升至22%，特别是在粤东重点修复海域NO_x排放量增加了2.7倍.原始轨迹在广东省海域较为稀疏，在粤东海域有明显轨迹缺失；轨迹修复后广东省海域船舶轨迹更为密集，粤东海域船舶轨迹得以补充，船舶排放空间分布更连贯.对比模拟结果与卫星观测结果，轨迹修复后粤东重点修复海域船舶模拟浓度与观测浓度的偏差由51%减至6%，总体上船舶排放模拟结果更接近卫星观测结果.

Ship emissions spatial characterization improved method and application based on AIS trajectory restoration

Characterizing ship emissions based on AIS data is currently the mainstream method for ship emission spatial characterization. But missing ship trajectories would cause ship emissions underestimated and spatial characterization errors, as well as affecting the air quality evaluation and division of emission control areas. In order to improve the spatial characterization of ship emissions, taking the 2013 AIS ship data of Guangdong waters as an example, this paper used the cubic spline interpolation method based on time and latitude and longitude to restore the AIS trajectories, and combined with the vessel engine-based approach to calculate ship emissions. Comparing the differences in ship emissions of original trajectory and after AIS trajectory restoration, we quantified the impact of ship trajectory restoration on ship emissions and ship spatial characterization. Finally, we compared air quality model simulations and satellite observations to evaluate the improvement effect of AIS trajectory restoration on ship emission characterization. The results show that after trajectory restoration, the total number of ship trajectory points in Guangdong waters increased from 4,685,773 to 5,764,664, and the NO_x emissions of ships increased by 0.6%. As for the eastern Guangdong waters where the trajectory points and emissions are missing concentratedly, after the trajectory restoration, the number of trajectory points increased by 88% and the NO_x emissions accounted for the ships emissions in Guangdong waters increased to 22%. In particular, the NO_x emissions of the key restoration waters in eastern Guangdong increased by 2.7 times. The original trajectories are sparse in Guangdong waters, and there are obviously missing trajectories in eastern Guangdong waters. After the trajectory restoration, ship trajectories in Guangdong waters are denser, the missing ship trajectories in the eastern Guangdong waters are supplemented, and the emissions spatial distribution is more coherent. Using the CMAQ model combined with satellite observations to assess the impact of trajectory restoration on the coastal areas of Guangdong, the ship simulation results after trajectory restoration are closer to satellite observations. The gap between simulated concentration and observed concentration of ship emissions in the key restoration waters in eastern Guangdong decreased from 51% to 6%.