This case lets you practice identifying dust with satellite imagery. It uses several products, notably the dust RGB, which is designed to monitor the evolution of dust storms. The product can be used both day and night, and is a composite of infrared channels IR 8.7, 10.8, and 12.0. Dust is shown in magenta colours. The case also uses the day natural colour RGB, which is made from three solar channels: VIS 0.6, VIS 0.8, and NIR 1.6. In this RGB, vegetation is green and bare ground is brown.
View the animations from 19 March 2010 0800 to 1145 UTC, looking for areas of dust. Then answer the question below.
Which of the following statements are true? Select all that apply.
The correct answers are A, B, D, and G.
The IR 10.8 channel shows a thick dust layer in dark grey colours. It is not very distinct in the early morning since dust clouds have nearly the same temperature as the surface. But during the day, thicker areas of dust are relatively easy to distinguish due to their contrast with the hot continent. Areas with thin dust are more difficult to see. This makes options A and B correct, and option C incorrect.
In day natural colour RGB, the dust areas are evident in the diffuse light brown belt over the southern Sahara and Sahel. Dust also appears over the Arabian Peninsula in a lighter brown colour than the surrounding areas.
In the dust RGB, the cyan colour indicates dry, hot land, while the shades of magenta indicate dust. The thickest dust is dark magenta. Over Arabian Peninsula, we see the dust front moving south during the day.
In summary, IR 10.8 imagery is not the ideal product for detecting dust since it only shows thicker dust clouds in daytime. It’s easy to miss thin dust clouds. In addition, the product does not distinguish clouds from dust. The day natural colour RGB is better for monitoring dust but can only be used during daylight hours. The dust RGB is best since it shows dust in unique colour (magenta) and works both night and day.