Exhaust gas emitted from the ship contains water soluble particles. Ship tracks occur when clouds form around the fine particles acted as nuclei in humid condition over the ocean.
Figure 1 shows an image observed by the GOSAT/TANSO-CAI of the ship tracks over the Atlantic Ocean on January 16, 2018. Figure 2 shows an image of the sea off the coast of Portugal enlarged within the red rectangle in Fig. 1. The clouds generated by exhaust gas emission from the ship look brighter because they have more water droplets than the general clouds. There are many streaky clouds showing ship tracks in Figs. 1 and 2. Many ships seem to navigate from the Mediterranean Sea toward North America, or from South America and Africa toward northern Europe.
The ship track clouds have an effect of cooling the Earth's surface due to highly reflecting solar radiations. However, there are many unclear processes to know the influence of this effect on a global scale. It is one of the most unknown effects in the climate science.
※The TANSO-CAI image was composed of band2 (674nm) in red, band3 (870nm) in green and band1 (380nm) in blue.
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