AIRS

Frequently Asked Questions


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Q.  What is the status of V5 water vapor for values < 10 ppmv. For V4
these data were heavily influenced by a priori values. Has that
changed for V5?  

A.  The 10 ppmv limit is close to our lower sensitivity threshold.
Sensitivity studies show we can discern the first ~0.1 mm of
precipitable water vapor (from above). This may or not be at 10 ppmv,
depending on the vertical distribution. The averaging kernels should
give us a better handle on when this cutoff occurs, but we haven’t
done the study.

The short answer is that the a priori will be a significant component
at 10 ppmv. The best reference is the Gettelman et al. (2004)
validation study.

Gettelman A., et al. (2004), Validation of Aqua satellite data in the
upper troposphere and lower stratosphere with in situ aircraft
instruments, Geophys. Res. Lett., 31, L22107, doi:10.1029/2004GL020730.

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