Can radiance value be negative?

[GES DISC - ingridgs]

Answer:

In general, AIRS can have negative radiances for shortwave channels. When the scene temperature is low, below 200K, shortwave AIRS channels can have negative radiances. This happens over very high cloud in tropics and over Antartica.

In bad channels, radiance can be negative for several different reasons:

1) -9999.0 is used as a flag value when input data is missing or out of range. Out of range data happens most frequently as a result of sun glint causing saturation.
2) Radiances can go negative when the noise is greater than the scene. This will happen in very noisy detectors (so users should check the channel properties file and/or the ExcludedChans field in the data. Note ExcludedChans is not defined correctly in the docs. Any channel with a value 3 or higher should be ignored. NeN is also a good diagnostic of channels experiencing transient high noise episodes.)

The users should be warned to use only the channels that are marked good ( BadFlag = 0 in the channel property file).