Hi Patrick,
I'm a bit confused with the error characterisations when comparing
QPack1 to Qpack2. For the unit='vmr' case, all is clear and consistent.
The use of unit= 'logrel' in Qpack2 resp. "Q.CLS_SPECIES_POS_ON = 1" in
Qpack1 (not x is retrieved but log(x/xa)) as in my retrieval case, leads
to inconsistencies in error calculation between Qpack1 and Qpack2 and in
QPack1 itself.
Error calculation:
Qp1: S_obs = (unitfac*unitfac') .* (Dy * Se * Dy'); %unitfac: in my
case the a-priori-profile, for the 'vmr' case a vector of ones
A = A - eye(nx,nx);
S_smo = A * Sx * A';
Qp2 : So = G * Se * G';
AI = A - eye(size(A,1));
Ss = AI * Sx * AI';
=> eo = sqrt(diag(S_obs)) resp. sqrt(diag(So)) and es =
sqrt(diag(S_smo)) resp. sqrt(diag(Ss))
=> es (Qp1)~ es (Qp2) but eo(Qp1)<<eo(Qp2)
Up to now, I assumed eo and es being relative to x for both versions.
The difference of the observation error obviously comes from the
application of unitfac in Qpack1.
In the QPack2 doc it is suggested to convert the L2 data of Qpack2 from
logrel to vmr with qp2_rel2vmr* (this includes errors and AVK), thus
the converted errors are also in absolute values. Surprisingly the
converted observation error is similar to the one of Qpack1. Does this
mean, that the observation error of Qpack1 in reality is given in
absolute values??. This would be inconsistent as at least es (Qpack1)
seems to be relative.
Further I'm not sure if it makes sense to also convert the averaging
kernel vom logrel to vmr, as in my case the converted AVK is completely
useless for me. E.g. the maxima are in the stratosphere (whereas the
unconverted AVK is similar to the AVK from Qpack1 with maxima in the
troposphere). Thus I tend to convert only x and xa by an own function.
Regards
René
* in the doc, sect. 6.4.3 a function called "qp2_rel2logrel" is
mentioned, but I think it should be "qp2_rel2vmr"
--
René Bleisch
Institute of Applied Physics
University of Bern
Sidlerstr.5
3012 Bern
Switzerland
Phone: +41 31 631 89 59
Mail: [email protected]
_______________________________________________
qpack mailing list
[email protected]
https://www.sat.ltu.se/mailman/listinfo/qpack
