Exercise


Below you will find three images, EX-1a (MSG image), EX-1b and EX-1c (MODIS images), showing the storm above Nigeria we have seen above. The MSG image (EX-1a) scanned the region at about 13:06 (the image header time relates to the beginning of the scan, thus the area of the storm was scanned about 6 minutes later), while the MODIS instrument on-board of the polar-orbiting Aqua satellite captured the storm at 13:09 UTC (about 3 minutes later after the MSG image). The pixel resolution of MSG for this area is about 3 km, resolution of MODIS is about 1 km.
For a full size view, click on the image

EX-1a. MSG image of the storm above Nigeria, color-enhanced IR10.8 band (190K-230K), taken at about 13:06 UTC. Letters A and B refer to two groups of overshooting tops, discussed below in the exercise description

EX-01b. MODIS image of the same storm, taken only about 3 minutes later. Color-enhanced band 31  BT (exactly the same color enhancement as in the MSG IR10.8 image above).
EX-01c. The same MODIS image as above (the same band 31), but shown with a slightly different color enhancement, 184K-230K. This enhancement shows the location and size of the coldest tops much better, as compared to the previous image.
If you compare the images carefully, you will see that the northern group of overshooting tops (labeled "A" in the MSG image) looks in the MSG image like one single large overshooting top only, while MODIS with its better resolution resolves at least two major overshooting tops there. The southern overshooting top (labeled as "B") looks weaker in the MSG image, and comparable (at first glance) to the other ones in the MODIS image. Brightness temperature of the northern overshooting tops (A) is about the same for both satellites, ~ 187 K.  This is not true for the southern overshooting top (B), which in the MSG data is at about 192 K, while in the MODIS image it is significantly colder, at 184 K. 


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