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Dust Over Greece
Posted April 22, 2005
Powerful winds pulled a thick band of desert dust from Egypt and Libya over the Mediterranean Sea on April 17, 2005. The dust is so thick that Crete is completely obscured from view, and the ground of Greece is barely visible. African dust frequently blows over the Mediterranean in the spring, carrying tons of dust into Greece. This particular storm shrouded the country in a yellow haze that cancelled or delayed flights and halted sea transport, according to local news reports. The winds that produced this dust storm blew at an average of 75-89 kilometers per hour (47-55 mph) near the sea s surface, and stronger winds prevailed higher in the atmosphere. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA s Aqua satellite captured this photo-like image of the storm.
NASA image courtesy Jeff Schmaltz, MODIS Land Rapid Response Team at NASA GSFC. The image is available in additional resolutions.
Smoke from Fires in Greece
Besides laying waste to huge areas of forest, fires burning in Greece in August 2007 released pollutants that traveled across the Mediterranean Sea and into Africa. This image shows aerosols—tiny solid or liquid particles suspended in air—observed by the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite layered on the photo-like Blue Marble composite image. Relatively clear air is transparent. Highest aerosol concentrations are pink.
On August 26, 2007, aerosols from the fires on the southwestern coast of Greece took a fairly direct route across the Mediterranean Sea to the western part of the Libyan coast. A large pool of smoke collected over the Gulf of Sirte, off the Libyan coast. Another pocket of thick aerosols appears over Algeria. These particles are probably smoke emitted from fires burning in Algeria over a long stretch of the coastal Atlas Mountains. Farther south over the deserts of northern Africa, the light green areas of moderate aerosol amounts could be smoke or dust.
On August 27, 2007, aerosols still crossed the Mediterranean Sea, but they took a more circular route. They spread southward in a clockwise direction from Greece, across the island of Crete, and concentrated thickly over eastern Libya. The other large pocket of aerosols—the pink patch hovering over the border of Libya and Algeria—may include smoke from Algeria and Greece. As on the previous day, some aerosols collected over Egypt and eastern Libya.
OMI detects the amount of light of different wavelengths that the atmosphere scatters back to space; the amount of backscattered sunlight is affected by what is in the atmosphere. To make an aerosol index with OMI data, scientists compare the amount of ultraviolet (UV) light the atmosphere scatters back at given place and time to the amount of UV light that the atmosphere would scatter back if it were totally clear.
You can download a KMZ file KMZ file of the smoke from Greece suitable for use with Google Earth for both August 26 and August 27.
Image courtesy Omar Torres, OMI Science Team, and Colin Seftor, NASA NPP Science Team.