Dear Facundo, What do you mean with "a little bit different"? A figure would have helped.
As soon as you involve a retrieval in test of this kind, you need also to consider the retrieval grid. In this case, the O3 profile will be interpolated, from the retrieval grid to Q.P_GRID and only this can introduce some disturbance. To keep this "disturbance small", it is a good idea that the retrieval grid is sub-set of the P_GRID, such every second point in P_GRID. Or if you do a test like this, why not set the retrieval grid to P_GRID. Just to be clear, no change in the profile is totally local, it has an effect out to the adjecent grid points. But I assume that you have some grids points between 7 and 12 km, and this is not an issue here. Anyhow, a change of O3 at 7 km should not affect upward measurements at 12 km. Note that things can be different for temperature and H2O as these quantities affect hydrostatic equilibrium, and a local effect propagates through the atmosphere. Regards, Patrick On 01/14/16 07:14, Facundo Orte wrote: > Dear Patrick and Ole Martin, > I am writing again from this old mail because I have a problem in Qpack2 > that I think that it is related with the setting that Ole Martin > proposed in the previous mail, but I am not sure. > To explain it I want to share the experiment that I did: > > 1. I set Y.Z_PLATFORM=12Km. My O3 a-priori profile goes from ground to > 90km (I will call it 'APRIORI') [So, then of the 3. step I will have a > simulated spectrum from the a priori (SPECTRUM_AP)] > > 2. I make a synthetic profile (taking it as O3 in the atmosphere or true > state vector)which is same as the a priori profile, but I add a delta O3 > (0.5ppm) at 7km (PROFILE_7km). So, I arrange a syntetic "true state" > that I know. Then I calculate a spectrum (SPECTRUM_7km) from PROFILE_7km > using QPack2/ARTS. I took this spectrum as the measurement. > > 3. I run Qpack2/ARTS inserting SPECTRUM_7km as measurement, and APRIORI > as a priori profile and stop in the first iteration. > > (Note that I am setting Y.Z_PLATFORM=12km, and I the add a delta O3 the > ozone in the true state vector at 7km. ) > > The result was that SPECTRUM_AP (yf) is a little bit diferent to > SPECTRUM_7km (y). I think that it must be equal (SPECTRUM_AP = > SPECTRUM_7km) because the Y.Z_PLATFORM is above to 7km and a > perturbation at 7km should not affect the retrieval. Is it correct? > > the Q is: Why changes below Y.Z_PLATFORM in the true state vector > affect the retrieval? > > Thanks in advance. > Best regards > Facundo > > > > > > > > 2014-11-18 21:58 GMT+09:00 Ole Martin Christensen > <[email protected] <mailto:[email protected]>>: > > Hi, > > the standard way of doing this is to do it before you do the > retrieval. You manually adjust your measured spectra assuming that > your measured opacity is correct (called "tropospheric correction"). > > In arts you can then model your instrument as being above the > troposphere, i.e. by setting the altitude of your sensor > (Y.Z_PLATFORM if you use qpack2) to 15 km. The simulated spectra can > then be compared to your corrected spectra for a successful retrieval. > > Another option is using continuum models to model O2, H2O(gas and/or > liquid) across the tropopause. These can be added by adding by > writing e.g.: > > Q.ABS_SPECIES(2).TAG = { 'H2O-PWR98' }; > > With a following fields like Q.ABS_SPECIES(2).ATMDATA, and > Q.ABS_SPECIES(2).GRIDS. > > However, in general the manual tropospheric correction is the most > commonly used method, as it is simpler, and would recommend starting > with this. > > If anything is unclear please feel free to send more questions. For > further inquiries I would also strongly recommend the qpack and arts > mailinglists. > > https://www.sat.ltu.se/mailman/listinfo/qpack > https://www.sat.ltu.se/mailman/listinfo/arts-users > > Regards > > Ole Martin > > > ------------------------------------------------------------------------ > *From:* Facundo Orte [[email protected] > <mailto:[email protected]>] > *Sent:* Tuesday, November 18, 2014 12:44 PM > *To:* Patrick Eriksson > *Cc:* Ole Martin Christensen > *Subject:* Re: Question about ARTS > > Dear Patrick Eriksson, > thanks for your reply. > The MWR is installed in Río Gallegos city (Latitud: -51° 36' > 02,03",Longitud: -69° 19' 09.96") since 2011. The name of the > observatory is "Observatorio Atmosferico de la Patagonia Austral" > which depends to Lidar Division (CEILAP). You can see the site in > this link http://www.division-lidar.com.ar/sitios_rg.html. It is > quite near to Ushuaia. > The MWR is working at 110.83GHz. For calculate the opacity from the > MWR we can use, for example, the method described by Zafra et al. > (Zafra, R. L., Parrish, A., Solomon, P. M and Barrett, J. W., A > Quasi-continuous record of atmospheric opacity at λ=1.1 mm over 34 > days at Mauna Kea Observatory, International Journal of infrared and > Millimeter Waves, Vol. 4, No 5, 1983.). Comparisons between the > opacity measured and obtained from radiosonde profiles presents good > agreement. > If I may to introduce the measured opacity (by MWR) as input of ARTS > maybe it could be good. My question is:where can I input the > measured opacity in ARTS? > Thanks a lot > Best Regards > Facundo > > > 2014-11-17 15:53 GMT-03:00 Patrick Eriksson > <[email protected] <mailto:[email protected]>>: > > Dear Facundo Orte, > > Nice to hear that you have started to use Qpack. > > Getting curious, where exactly is the radiometer placed? Did > some travelling around Latin America in the 90-ies. Passed e.g. > Uschaia. What frequency is the radiometer using? > > Don't understand your question exactly. How do you observe an > opacity with the radiometer? I don't know how that could be > done. Measured brightness temperatures can be converted to an > opacity, but then it is better to use the original Tb-data. Or > is the opacity determined by some other instrument. If you > describe this closer, we will try to help you. > > Regards, > > Patrick > > > > On 2014-11-17 19:05, Facundo Orte wrote: > > Dear Patrick Eriksson, > My name is Facundo Orte and I am a PhD student of the Lidar > Division of > CEILAP (Laser Research Center) from Argentina > (division-lidar.com.ar <http://division-lidar.com.ar> > <http://division-lidar.com.ar>__). > I am writing you because in our laboratory there is a > Millimiter Wave > Radiometer (MWR) instaled in South Patagonia, near to the > spring ozone > hole, and we retrieve ozone profiles with it. To analyze the > signal we > are trying to use the ARTS model that you and your team > developed. I am > using MATLAB to introduce inputs changing Q.DEFINITION.m > function and I > retrieve some profiles but there are quite close to "a > priori" ozone > profile (I am using MLS climatology as a priori O3 profile). > I think > that it is because I do not have well caracterized the > atmosphere and I > am trying to do that. For example, at this moment, I do not > know how to > introduce the opacity measured for the MWR instrument from > MATLAB as > input and I think that it is an important parameter to > introduce. > Could you help me with it? Do you know how I can to > introduce the > opacity from MATLAB? > I will very appreciate if you can help me with it. > Thank you in advance > Best regards > Facundo Orte > > > > > _______________________________________________ qpack mailing list [email protected] https://www.sat.ltu.se/mailman/listinfo/qpack
