AIRS Near-Real Time
AIRS Near-Real-Time (NRT) data production at GES DISC frequently helps deliver imagery that can serve as a timely alert for events that can be potentially dangerous or harmful. This imagery is typically available only a couple of hours after the Aqua satellite overpasses a certain region - at the Equator, Aqua ascends at around 13:30 local time. An example event of this type is the recently observed gigantic dust storm over the West Coast of Africa. This event lasted for more than three days (March 21-24, 2010) and was still continuing at the time of this article publication on March 24. The storm blasted dust clouds over a large region, affecting thousands of square miles on the African continent. The appearance of this event was somewhat like an early onset of easterly trade winds. The four-day sequence of images below shows fine-resolution (3-km), false-color imagery from AIRS visible bands.
News link: Nigeria shrouded in dust, flights canceled
The AIRS NRT imagery is available through the GES DISC Web-Map-Service (WMS). E.g. the current day false-color browse (like the one above) can be manipulated by varying this url. (Note: if the Web Map server is down, which happens occasionally, this link will be empty.
For more information, read AIRS NRT data and services.
When the routine-production data become available, events like this can be previewed in more detail using the A-Train Giovanni portal. The A-Train portal collocates and subsets AIRS data along the CloudSat and CALIPSO track, and adds a vertical dimension to the investigation. For example, it would be interesting to make a preliminary assessment of the altitude of the atmospheric layers that accommodate the dust. Since the dust is blown from very dry areas of the African continent, it is reasonable to expect that the dust layer will be distinctively dryer from its surroundings. Hence, it makes sense to look for dryer intrusions in the AIRS- and model-humidity profiles, in the plate below. Indeed, if taking AIRS and collocated ECMWF model profiles from March 21, off West Coast of Africa, the dry layer is clearly seen between 900-700 mb in the model data, and to some extent in AIRS retrievals (AIRS standard retrievals have only two layers in between 900-700 mb). The latitudinal-horizontal extent of the dust layer can be conveniently corresponded using the collocated MODIS/Aqua Aerosol Optical Thickness, bottom of the plate. The small values of the MODIS small mode fraction are an indication that the dust layer consists of predominantly coarse dust particles.