Hi Gerrit, I am on vacation and the answer will be very short.
This differs if the conversion is done in yCalc or in yApplyUnit. If done in yCalc, the conversion is performed for each monochromatic frequency and the spectral response is applied on the Tb values. If done in yApplyUnit, the conversion will be done for y_f, that should match f_backend. I can not answer if any of this will match exactly what is done for ATSR. Internally we have had similar discussions around AMSU, ICI ... It is surprising that the mimicking the calibration is quite problematic. We can discuss further when I am back at work Aug 3. Bye, Patrick On 07/17/15 18:48, Gerrit Holl wrote: > [reposted to arts-users instead of arts-dev] > > Hi, > > when ARTS converts a channel (i.e. polychromatic) radiance from one > unit to another, such as in yApplyUnit or directly in yCalc, does it > take into account the finite width of channels? The NOAA KLM User's > Guide provides band corrections (see, for example, Equation 7.3.3-4 > and Table D1-4) to compensate for the fact that using the central > wavenumber when inverting the Planck function for a radiance > integrated over a finite spectral width is not correct. I'm told ATSR > simulations use lookup tables. As far as I can tell, ARTS uses only > the central frequency (f_backend) but I might be missing something as > it's all folded into the sensor_response optimisation so not very easy > to follow. What I'm looking for is the physically correct way to do > the conversion (with a secondary aim to quantify how large an error is > introduced by approximating it monochromatically). > > I found a forum discussion at > http://www.nwpsaf.eu/forum/viewtopic.php?f=8&t=184 where James Hocking > links to an old NOAA Technical Report (Weinreb et al, 1981) at > http://babel.hathitrust.org/cgi/pt?id=uiug.30112106578377;view=1up;seq=12 > . > > What does ARTS do? > > regards, > Gerrit. > _______________________________________________ > arts-users mailing list > [email protected] > https://www.sat.ltu.se/mailman/listinfo/arts-users > _______________________________________________ arts-users mailing list [email protected] https://www.sat.ltu.se/mailman/listinfo/arts-users
