Last update: October 23rd, 2019 at 9:31 am
These photographs were taken as astronauts aboard the International Space Station flew over the headlands of the southern Brazilian port city of Florianópolis. The east side (top right) and west side (lower left) are joined by bridges spanning the 400-meter-wide narrows. The International Airport of Florianópolis appears on the lower right. The city has one of the highest-quality-of-life indices in Brazil.
The top image is illuminated by the partial reflection of the Sun. This sunglint reveals many details in the water surface, especially wind streaks and boat wakes. The water south of the city is far brighter than to the north, probably because the hills of the city protect water surfaces from the wind on the leeward side, leading to calmer water and a brighter reflection. On the day of the photograph, the winds were blowing from the north (upper left), meaning waters were calmer south of the city.
Astronauts gain a sense for the sunglint point moving across Earth’s surface as the ISS is orbiting the planet. These images are an example of the training crews receive in the special effects inherent in near-glint-point images of water bodies. The second photo was taken just 31 seconds after the glint point had moved off the view, and it shows quite different features in the water—especially the brown, muddy outflow of a small stream that enters the bay near the airport. Most coastlines show faint brown tinges in the water; these arise from wave action stirring up shoreline muds, as well as from city pollution.