Taking a different approach, the scientists at the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) have developed a method of processing satellite imagery specifically designed to aid the detection of atmospheric dust. Unfortunately, these types of images are only available in the daytime, which presents a problem for scientists trying to track the development and distribution of atmospheric dust clouds over time. In these so-called "false-color" images, such as in the one of China's Taklimakan Desert, dust clouds show up quite clearly, even over lighter areas. In response, scientists have tried to take advantage of the technological advances in satellite instrumentation to create different types of satellite imagery to overcome this dust-detection difficulty.įor example, Suomi NPP's VIIRS instrument, a more advanced instrument compared to its predecessors, allows scientists to create photorealistic images of Earth by combining three (red, green, and blue) of VIIRS's 22 channels. For example, in visible satellite imagery, which is grayscale (see GOES image), it can be difficult to see dust clouds over light-colored backgrounds or distinguish them from other cloud types. Why? More often than not it comes down to color. Of course, just because satellites can detect dust in the atmosphere does not mean scientists can always detect it in satellite imagery. (Note the large plumes of aerosols from sand, dust and salt-spray moving westward, off the coast of Africa.) Dust Detection Difficulties
In the map of AVHRR and VIIRS aerosol optical thickness data (shown above), areas of the atmosphere with thick aerosol layers (i.e., areas in which a lot of light is reflected or absorbed) are colored in deep orange, whereas areas with low aerosol optical thickness are colored light yellow.
Satellite sensors, such as the GOES I-M Imager aboard the GOES-13 and -15 satellites, the Advanced Very High Resolution Radiometer (AVHRR) aboard the NOAA-series satellites, and the Visible Infrared Imager Radiometer Suite (VIIRS) aboard Suomi NPP, can detect these areas of reflection and absorption, thus indicating varying amount of aerosol in the atmosphere. If you're wondering how a satellite travelling 22,236 (or 512) miles above the Earth's surface can even detect something as small as dust in the first place, it's because dust, like other aerosols in the atmosphere, reflects or absorbs light.
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