Satellite-Based Estimates of Individual Ship NO _<i>x</i> Emissions

The accuracy of ship NOx emissions remains uncertain due to their dependency on the combustion process. Here, we introduce an approach named the Satellite-Based Individual Ship Emission Model (SISEM) for estimating NOx emissions from individual ships using satellite measurements of 2020. By applying SISEM, we derived the NOx emission rates of 141 ships in the central Mediterranean, considering the transport pattern and chemical decay. A comparison with the current ship emission inventory model shows that the SISEM estimates differ by −17 to +700% when averaged by ship type, which may be partly attributed to environmental conditions such as wind. Notably, the effects of sailing with and against the wind on NOx emissions are asymmetric and cannot be offset by each other. Additionally, a decrease of 10% was found in the ship NOx emission in the Mediterranean Sea when using the combined effects of environmental and ship conditions as a correction. This study implies the feasibility of monitoring ship NOx emissions through satellite.