Improving the estimation of ship emissions using the high-spatiotemporal resolution wind fields simulated by the Weather Research and Forecast model: A case study in China

Ships, sailing in favorable wind or obstructed by wind, will operate with different output power of the engines, and the exhaust emissions will be different even though the ships are sailing at the same ground speed. In this study, the influence of wind was taken into consideration; the ship emission inventory (0.025 degrees x0.025 degrees) in China of a full year (2014) was reassessed. A speed modification model was employed to figure out the actual output speed of ships by integrating AIS data and the hourly wind. The Weather Research and Forecast (WRF) model was applied to predict the hourly real-time wind field. The spatial and temporal changes in emissions between the results calculated by the proposed method and our previous study were presented. Overall, when considering the influence of wind, the total ship emissions for the year would increase. In this study, the total estimated emissions of SO2, NOx, PM10, PM2.5, HC, and CO in the area were 1.286 x 10(6), 2.583 x 10(6), 2.135x 10(5), 1.967 x 10(5), 1.522 x 10(5), and 3.053 x 10(5) t(metric tons) in 2014, respectively. Under the influence of wind, the proportion of the regions' emissions to the total was close to that of the previous study. For SO2 and NOx, emissions presented significant monthly variations. On a monthly timescale, the difference in emissions was more obvious between the results considering and not considering the wind, relative to that on a yearly basis. This study adjusted the method of ship emission estimation, which modified the ship emission inventory over an hourly timescale.