In the summer months in the Northern Hemisphere, dust storms originating in
the deserts around the Arabian Peninsula have a significant impact on the
amount of solar radiation that reaches the surface. Winds sweep desert sands
into the air and transport them eastward toward India and Asia with the
seasonal monsoon. These airborne particles absorb and deflect incoming
radiation and can produce a cooling effect as far away as North America.
According to calculations performed by the NASA Goddard Institute
for Space Studies (GISS), the terrain surrounding the southern portions
of the Red Sea is one of the areas most dramatically cooled by the presence
of summertime dust storms. That region is shown experiencing a dust storm in
this true-color image from the Moderate Resolution Imaging Spectroradiometer (MODIS)
acquired on July 11, 2002. The GISS model simulations indicate that between
June and August, the temperatures would be as much as 2 degrees Celsius warmer than they
are if it weren't for the dust in the aira cooling equivalent to the
passage of a rain cloud overhead.
The image shows the African countries of Sudan (top left), Ethiopia (bottom
left), with Eritrea nestled between them along the western coast of the Red
Sea. Toward the right side of the image are Saudi Arabia (top) and Yemen (bottom) on the Arabian
Peninsula. Overlooking the Red Sea, a long escarpment runs along the western
edge of the Arabian Peninsula, and in this image appears to be blocking the
full eastward expansion of the dust storm.
Which came first, the clouds or the dust? Both clouds and dust can be important factors influencing regional climate, and they are frequently observed together. In this view taken from the International Space Station, two images were merged to create a mosaic of a dust storm and thunderstorm over the Red Sea. By interpreting the mosaic, we make a guess about which came first.