Hallo René, Things to look at, perhaps:
- Are the absorption settings really the same (same H2O continuum, etc.)? - What is the vertical grid spacing of your atmoshere? If this is relatively coarse, it may be a good idea to set: "NumericSet( ppath_lmax, 250 )" in the controlfile. (The default value for this in general.arts is 1000, which is a bit large.) /Stefan On Jun 16, 2011, at 14:21 , Rene Bleisch wrote: > Hi Patrick, > - Sensor/backend: removing the sensor/backend part lead to no > improvements, the differences are still the same > - Forward model: For the same example a-priori vmr, Arts1 delivers a > spectrum with 43.1 K at the center frequency of 22.235 GHz, Arts2 a > spectrum with only 39.7 K (Rayleigh-Jeans BT) resp. 40.2 K (Planck BT) > at 22.235 GHz using the settings from the retrievals, the deviation > slightly increases with frequency. Thus choosing Planck or RJ matters, > but the difference is small (only 0.5 K in the example). > > Hence the problem obviously seems to be in the Forward modelling and not > in the retrieval itself. I will now carefully go through the entire > forward model setup for both versions (which should be the same). > > Regards, > René > > > PS: During the tests with no sensor/backend part, I discovered that > Qpack2 ends with an error, if y is chosen in L2_EXTRA and the > sensor/backend are disabled. > Qpack2 then crashes because qp2_l2 takes L2.f from Q.SENSOR_RESPONSE_F > (line 137). But as the backend is disabled, neither this variable > (containing the name of the xml-file with the sensor-response frequency > grid) nor the xml-file itself are created during the processing. > > > > On 15.06.2011 14:47, Patrick Eriksson wrote: >> Hi René, >> >> My answer is in line with the one of Stefan. The first step is to >> check if you get the same spectrum from the two forward models, for >> the same input. That is, no inversions involved. First test without >> sensor. And if OK, include also the sensor. >> >> Looking a bit on the retrieval part. The logrel unit is the most >> tricky one. If the tests above are all OK, please compare weighting >> functions for rel/frac. >> >> Just ask if anything is unclear. I want of course to know if there is >> a bug soemwhere. That can happen even in ARTS/Qpack ;-) >> >> Bye, >> >> Patrick >> >> On 06/15/2011 12:47 PM, Rene Bleisch wrote: >>> Hi all, >>> I use Qpack to retrieve tropospheric water vapour profiles from spectra >>> of our 22GHz radiometer MIAWARA. The setup is like this: >>> - nonlinear Marquardt-Levenberg >>> - polyfit (1st grade, coefficients are part of the state vector and are >>> retrieved) >>> >>> Till recently, I used the old Qpack1 and it worked well. Some months ago >>> I started trying to setup the same retrieval with QPack2. As it didn' >>> work well and I had a lack of time, I gave it then up. Now I retried it >>> and it works quite well with QPack2 after setting the retrieval unit to >>> logrel (implicitly the Qpack1-retrieval was set to logrel, what I only >>> discovered thanks to Patriks suggestions). >>> >>> Still the results with QPack2 differ from the results with QPack1, as >>> the vmr is generally up to 20% too low in upper troposphere and 10-20% >>> too high in lower troposphere. More detailed analyses revealed that >>> there is a difference between the weighting functions in Qpack1 and >>> Qpack2 (even in the first iteration step), the tropospherical maxima of >>> the weighting functions in Qpack2 are generally up to 10% lower than in >>> Qpack1. >>> >>> Does anyone have an idea where this difference could come from? >>> (spectroscopy and pTz setup are identical) >>> >>> Maybe it has to do something with the sensor/backend-part, which should >>> in principle be the same for both. In Qpack1 the H-matrix (y=H*F(x,b)) >>> summarizes the entire sensor/backend stuff. I wanted to compare H with >>> its equivalent in QPack2, but I could not find it. Does there exist a >>> similar H-matrix in Arts2/QPack2? >>> >>> Regards >>> René >>> >>> >> > > -- > 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 _______________________________________________ qpack mailing list [email protected] https://www.sat.ltu.se/mailman/listinfo/qpack
