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April 24, 2025 - Dust and Sunglint over Cape Verde Islands
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Fierce winds carried dust from the Sahara Desert westward on April 22, 2025, turning the skies off of western Africa and the Cabo Verde Islands tan. Such dust storms are common and may occur at any time of the year. At times, Saharan dust can travel as far as South America.
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired this true-color image on that same day. Not only does the image show tan dust moving off Africa, but it also captures an interesting optical phenomenon called sunglint.
The bright silvery color on the left side of the image is known as “sunglint”. It occurs when sunlight reflects off the surface of the water at the same angle that a satellite sensor views it. Sunglint occurs regularly in satellite imagery, creating a long silver swath each time the sensor and viewing angle over water match up.
In this case, the sunglint shows how the strong northeasterly winds affect the surface of the water as it blows around the islands. When the surface of the water is smooth, sunglint shows a mirror-like silvery color. Where the surface of the water is rippled by wind, sunlight is reflected in many directions, so not all of it strikes the sensor. This creates dark areas where the water is roughened. When wind blows around islands, the quietest water is directly behind the island (on the lee side), where the wind is the weakest, so sunglint is most obvious in those areas.
Image Facts
Satellite:
Aqua
Date Acquired: 4/22/2025
Resolutions:
1km (1.3 MB), 500m (4 MB), 250m (6.6 MB)
Bands Used: 1,4,3
Image Credit:
MODIS Land Rapid Response Team, NASA GSFC
Fierce winds carried dust from the Sahara Desert westward on April 22, 2025, turning the skies off of western Africa and the Cabo Verde Islands tan. Such dust storms are common and may occur at any time of the year. At times, Saharan dust can travel as far as South America.
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired this true-color image on that same day. Not only does the image show tan dust moving off Africa, but it also captures an interesting optical phenomenon called sunglint.
The bright silvery color on the left side of the image is known as “sunglint”. It occurs when sunlight reflects off the surface of the water at the same angle that a satellite sensor views it. Sunglint occurs regularly in satellite imagery, creating a long silver swath each time the sensor and viewing angle over water match up.
In this case, the sunglint shows how the strong northeasterly winds affect the surface of the water as it blows around the islands. When the surface of the water is smooth, sunglint shows a mirror-like silvery color. Where the surface of the water is rippled by wind, sunlight is reflected in many directions, so not all of it strikes the sensor. This creates dark areas where the water is roughened. When wind blows around islands, the quietest water is directly behind the island (on the lee side), where the wind is the weakest, so sunglint is most obvious in those areas.
Image Facts
Satellite:
Aqua
Date Acquired: 4/22/2025
Resolutions:
1km (1.3 MB), 500m (4 MB), 250m (6.6 MB)
Bands Used: 1,4,3
Image Credit:
MODIS Land Rapid Response Team, NASA GSFC
