AIRS

Frequently Asked Questions


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Q.  Has the brightness temperature in the AMSU-A L1B product has been NADIR-
adjusted? If so is the error included in the product itself?  

A.  We do not adjust the MW and IR L1B radiance products to nadir.

We prefer to leave the measured radiances pristine. Instead, our
rapid transmittance algorithms (RTA) used in the retrieval steps to
create the L2 products have the zenith angle incorporated.

The IR L2 cloud-cleared radiances are adjusted to the center of the
associated AMSU footprint, which amounts to a 1.1 deg angle
adjustment. We do not adjust those radiances to nadir either.

The L1B radiance product reports for AMSU both an antenna temperature
and a brightness temperature.

The antenna temperature, antenna_temp, is the observed radiance.

The brightness temperature, brightness_temp, is the observed radiance
corrected for scan angle dependent sidelobe pickup (sidelobes pick up
the Aqua spacecraft). The correction is empirically derived.

The uncertainty in the empirically derive brightness_temp bias
correction is provided in brightness_temp_err. This term excludes the
radiometer noise.

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