Step 2: Select Appropriate Channels or Channel Derivatives

Here are the solar, water vapor, and longwave infrared groups of MSG channels for this daytime dust storm over northern Africa.

Chart of the MSG visible, water vapor, and longwave IR channels that can be used for creating the dust RGB.

Which channel group best depicts the boundary of the advancing dust front? See the area within the ovals in the 0.6 µm Vis and 10.6 µm IR images. (Choose the best answer.)

The correct answer is C.

The longwave channels (8.7 µm infrared and longer wavelengths) do the best job since dust contrasts with the thermal background, highlighting the dust front distinctly.

The solar channels are not the best choice here since the reflective dust tends to blend in with the bright desert background.

The water vapor channels cannot detect dust and land features since they do not see down to the surface boundary layer where the dust often resides.