TOMS and AVHRR: An Observational Comparison

We've obtained the Advanced Very High Resolution Radiometer (AVHRR) brightness temperature difference (10.8 micron - 12 micron channel) measurements for the August 19, 1992 ash cloud from our colleagues at Michigan Technological University. On this day, measurements from TOMS were taken within minutes of those from AVHRR, so it's a great opportunity to compare the two data sets.

The GIF image above compares the aerosol index from TOMS with the AVHRR brightness temperature difference (which is in degrees Celsius). Also shown in this figure is the reflectivity determined independently by the two instruments, which indicates that there is a cloud layer below the ash. Apart from the difference in resolution between the two instruments, notice that the ash cloud patterns are quite close, indicating an extremely good correlation between the two measurements (the similarity in scale magnitudes is coincidental). We are presently working to convert our aerosol index measurement into a 380 nm optical depth which we can then compare to optical depths calculated from AVHRR.