Hi Jana,

Are you just interested in the Jacobian or will you also perform retrievals (by Qpack?)?

our main issue here is to understand what unit logrel(O3) implies. following Patrick's advice from the previous (wind) thread, I checked the AUG (and the correct one for that matter - cause we're still using arts2.2; 'logrel' retrieval unit seems to be gone in arts2.3) - et voila!
(it's sec. 16.4 for all others interested in the matter)
so, according to my understanding of Sec16.4, 'logrel' is (at least regarding the Jacobian output) identical to 'rel', which in turn for the (semi-)analytical jacobians corresponds (or, is scaled) to a 100% change in the abs species (here, O3) with respect to the species' VMRs (as given by the vmr_field interpolated to the species' Jacobian p_grid). Is that understanding correct?

I would say yes. In my words: If we denote "logrel" as z, then z=log(x/xa). That is you retrieve the log of ratio with respect to a priori.

logrel and rel give identical results for the first iteration of a retrieval. But differ for later iterations (handled by Qpack).

and how is that for 'vmr' then? would the jacobians correspond to a '1' (or 10^6 ppm) change in the species? or a 1ppm change? (i'm unsure what VMR's SI unit is...).

All Jacobians are for a unit change, so here it is "1!. That is, what change would you get if you add a full atmosphere of the gas of concern.


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