Great to hear :) Q.F_GRID is the grid defining the pencil grid frequencies regardless of whether qpack2 or arts_y is used. qpack however is designed to be run with some sort of sensor (since ground based microwave retrieval is its main purpose) and thus I'm not entirely certain what happens if you run qpack with "sensor_do = false" with regards to back-end frequencies and sensor_los etc, but it should be reasonably easy to figure out is you analyze the qpack2.m file.
anyway glad to hear that everything worked out in the end Ole Martin ________________________________________ From: Pauline Martinet [[email protected]] Sent: Wednesday, May 20, 2015 5:25 PM To: Ole Martin Christensen Cc: Patrick Eriksson; [email protected] Subject: Re: [Qpack] monochromatic pencil beam calculation Dear Ole Martin, It is working now, I am very sorry it was totally my fault. When I added the call to the function arts_y I forgot to comment the call to QPACK2 and in fact the error message was coming from the call to QPACK2 not the call to arts_y. Now I have reasonable values for the pencil beam calculation ! Thank you so much, you really helped me :-) Just to be sure: the variable Q.F_GRID is thus only used with arts_y ? Thanks again, Best regards, Pauline ----- Météo-France ----- Dr. Pauline Martinet Chercheur CNRM/GMEI/LISA [email protected] Fixe : +33 561079031 Site web: www.sites.google.com/site/martinetpauline31 ----- Mail original ----- De: "Ole Martin Christensen" <[email protected]> À: "Pauline Martinet" <[email protected]> Cc: "Patrick Eriksson" <[email protected]>, [email protected] Envoyé: Mercredi 20 Mai 2015 16:32:26 Objet: RE: [Qpack] monochromatic pencil beam calculation Ok I'm out off suggestions, but I have some questions 1. What is Q.Z_FIELD(2)? 2. What happends if you put Q.Z_FIELD(1) = 0? The error message did change from the two mails you have sent, i.e. something is happening, maybe experiment a little to see which variable matters: "The ppath starting point is placed 0.0565856 km below the surface." to "The ppath starting point is placed 0.0535856 km below the surface." Sorry for not being able to help more. Ole Martin ________________________________________ From: Pauline Martinet [[email protected]] Sent: Wednesday, May 20, 2015 2:29 PM To: Ole Martin Christensen Cc: Patrick Eriksson; [email protected] Subject: Re: [Qpack] monochromatic pencil beam calculation Dear Ole Martin, I tried your solutions but it does not change my problem, I turned off the HSE, I tried to put my sensor a bit higher (even really much higher) but I still get the error message: These are the last values I tried: Q.SENSOR_POS=553; Q.Z_surface=53.86; Q._Z_FIELD(1)=53.86 Simulating spectrum 1/1 Run-time error in controlfile: /tmp/atmlab-martinet-tp033db076_e367_4931_9ac0_6f5b361b24df/cfile.arts Run-time error in method: yCalc Run-time error in function: iyb_calc Run-time error in agenda: iy_main_agenda Run-time error in method: iyEmissionStandard Run-time error in agenda: ppath_agenda Run-time error in method: ppathStepByStep The ppath starting point is placed 0.0535856 km below the surface. Stopping ARTS execution. Goodbye. Thank you Pauline ----- Météo-France ----- Dr. Pauline Martinet Chercheur CNRM/GMEI/LISA [email protected] Fixe : +33 561079031 Site web: www.sites.google.com/site/martinetpauline31 ----- Mail original ----- De: "Ole Martin Christensen" <[email protected]> À: "Pauline Martinet" <[email protected]> Cc: "Patrick Eriksson" <[email protected]>, [email protected] Envoyé: Mardi 19 Mai 2015 16:32:42 Objet: RE: [Qpack] monochromatic pencil beam calculation Do you have Q.HSE = on? If so it could be that the hydrostatic equilibrium changes you pressure-altitude relationship such that the instrument is placed under ground. There are three things that could help: 1. place your instrument a bit higher (e.g Q.SENSOR_POS = 100) 2. Turn of HSE 3. ensure that the reference level for the HSE calculations is a the same pressure level as your instrument 4. move the surface further down (Q.Z_SURFACE = -100) (but should not be outside z_field) Ole Martin ________________________________________ From: Pauline Martinet [[email protected]] Sent: Tuesday, May 19, 2015 4:16 PM To: Ole Martin Christensen Cc: Patrick Eriksson; [email protected] Subject: Re: [Qpack] monochromatic pencil beam calculation Hi Ole Martin, I have declared all the Q fields you mentioned. But I still have this error message that I don't understand (I tried to modify the variable Q_Zsurface or the variable ppath_lmax but it did not work): Run-time error in controlfile: /tmp/atmlab-martinet-tp07e89d96_0390_4f23_8673_9ee227f46cc1/cfile.arts Run-time error in method: yCalc Run-time error in function: iyb_calc Run-time error in agenda: iy_main_agenda Run-time error in method: iyEmissionStandard Run-time error in agenda: ppath_agenda Run-time error in method: ppathStepByStep The ppath starting point is placed 0.0565856 km below the surface. Stopping ARTS execution. Goodbye. Thank you Pauline ----- Météo-France ----- Dr. Pauline Martinet Chercheur CNRM/GMEI/LISA [email protected] Fixe : +33 561079031 Site web: www.sites.google.com/site/martinetpauline31 ----- Mail original ----- De: "Ole Martin Christensen" <[email protected]> À: "Pauline Martinet" <[email protected]> Cc: "Patrick Eriksson" <[email protected]>, [email protected] Envoyé: Mardi 19 Mai 2015 14:51:31 Objet: RE: [Qpack] monochromatic pencil beam calculation arts_y is a bit lower level function than qpack2 and as such the structures and fields need to be closer to how ARTS defines them. If you open the qpack2.m (subfunction qp2_y2Q) file you can see that it uses functions such as Q.VMR_FIELD = qarts_vmr_field( Q, mjd, ho ); Q.T_FIELD = qarts_atm_field( Q, 't', mjd, ho ); Q.Z_FIELD = qarts_atm_field( Q, 'z', mjd, ho ); as well as: Q.LAT_TRUE = Y(m).LATITUDE; Q.LON_TRUE = Y(m).LONGITUDE; to define the fields you mention. You probably need to do the same thing before running arts_y. Ole Martin ________________________________________ From: Pauline Martinet [[email protected]] Sent: Tuesday, May 19, 2015 2:44 PM To: Ole Martin Christensen Cc: Patrick Eriksson; [email protected] Subject: Re: [Qpack] monochromatic pencil beam calculation I have tried to use arts_y but I had to add these fields: -Q.T_FIELD -Q.VMR_FIELD -Q.Z_FIELD -Q.LAT_TRUE -Q.LON_TRUE Are they specific to arts_y ? Can I comment the declaration of these variables when I use qpack2 to simulate the spectra ? I activate the hydrostatic equilibrium, I am not sure about if I should or not. I have an error message: The ppath starting point is placed 0.0535856 km below the surface. I have defined Q.Z_SURFACE as the first level of my Q.Z_field vector. In my case it is 53 m. And I set the Q.PPATH_LMAX to 50. Do you see the problem ? Thanks, Pauline ----- Météo-France ----- Dr. Pauline Martinet Chercheur CNRM/GMEI/LISA [email protected] Fixe : +33 561079031 Site web: www.sites.google.com/site/martinetpauline31 ----- Mail original ----- De: "Ole Martin Christensen" <[email protected]> À: "Pauline Martinet" <[email protected]> Cc: "Patrick Eriksson" <[email protected]>, [email protected] Envoyé: Mardi 19 Mai 2015 11:38:59 Objet: RE: [Qpack] monochromatic pencil beam calculation ok good that you are starting simple :) to use arts_y just type "help arts_y" in matlab. it is a bit simpler to use that qpack2 since no retrieval or measurement definitions are used (only forward model settings). The syntax is: y = arts_y(Q) where y is a spectrum simulated using the arts control file generated by Q. Ole Martin ________________________________________ From: Pauline Martinet [[email protected]] Sent: Tuesday, May 19, 2015 11:36 AM To: Ole Martin Christensen Cc: Patrick Eriksson; [email protected] Subject: Re: [Qpack] monochromatic pencil beam calculation Hi Ole Martin, I agree with you this is why I am trying to compare my radiative transfer models with simple pencil beam simulations in one direction (90° at the moment) and this is where I saw I have unreasonable values when I put sensor_do to false. For the gridsize of the atmosphere, I am using my input profile (from an NWP model) to define my Q.P_GRID and I use this grid for the other radiative transfer model. I am sorry but I don't know how to use the arts_y function ? I am using Qpack2 at the moment. Thank you again ! Pauline ----- Météo-France ----- Dr. Pauline Martinet Chercheur CNRM/GMEI/LISA [email protected] Fixe : +33 561079031 Site web: www.sites.google.com/site/martinetpauline31 ----- Mail original ----- De: "Ole Martin Christensen" <[email protected]> À: "Patrick Eriksson" <[email protected]>, "Pauline Martinet" <[email protected]> Cc: [email protected] Envoyé: Mardi 19 Mai 2015 11:30:21 Objet: RE: [Qpack] monochromatic pencil beam calculation To do proper pencil beam simulations I will strongly recommend you to use the function "arts_y", to ensure that you are not overriding some of your Q settings with the measurement structure Y (I assume you are running qpack2 now?). furthermore if you are cross comparing different Radiative Transfer models I would start with very simple pencil beam simulations looking in one direction to ensure that nothing in the instrument simulation is different. As Patrick mentions there are lot of details to check (e.g. ppath_step_length, O2 parametrization and gridsizes of the atmosphere) so try and make them agree on as simple a case as possible before incorporating any advanced features. Ole Martin ________________________________________ From: Patrick Eriksson Sent: Tuesday, May 19, 2015 11:09 AM To: Pauline Martinet; Ole Martin Christensen Cc: [email protected] Subject: Re: [Qpack] monochromatic pencil beam calculation Hi Pauline, Regarding the second part. If you have a very high absorption, try to set Q.PPATH_LMAX to e.g. 50 m. In this way, the optical thickness of each ppath step will be smaller, which should improve the accuracy for opaque situations. Is the same oxygen absorption model used in the different codes? This is another possible cause to the differences. Bye, Patrick On 2015-05-19 10:26, Pauline Martinet wrote: > Dear Ole Martin, > > Thank you for your quick answer. > > I probably made a mistake on the definition of the frequency grid. > > H.F_BACKEND is defined as a vector of 14 values (in the capt structure > that is an input to my Q file see attached file) : > [22.24 , 23.04 , 23.84 , 25.44 , 26.24 , 27.84 , 31.40, 51.26 , 52.28 , > 53.86 , 54.94 , 56.66 , 57.3 , 58] > > Whereas Q.F_GRID is defined as : > Q.F_GRID = linspace (fc(1)-df(1)*0.51, fc(end)+df(end)*0.51,100)'; > > with df the spectral bandwith of the receivers : > df = 1e6 * [230 230 230 230 230 230 230 230 230 230 230 600 1000 2000 ]'; > > I thought Q.F_GRID would define the spectral resolution of the > line-by-line calculation of ARTS but it is not clear for me... > > By the way I have now a second problem. I am comparing ARTS with two > radiative transfer models and we have a 1.5 K difference in the most > opaque channels. > Theses channels should see approximately the same values as the > temperature profile in the lowest layers. In my case the lowest values > of my temperature profile are: > 285.0548 > 284.9542 > 284.7708 > > for the first three atmospheric levels > > but my brightness temperatures are too low (these are the most opaque > channels of the O2 band at 56.66, 57.3 and 58 GHz): > 283.6000 > 283.8423 > 283.9169 > > it seems like my sensor is upper in the atmosphere but my Q.Z_surface is > set to 0. > > I am also working in 1D but as I created the ATMDATA of the temperature > profile by reading the climatological file cira86 I have a 4D field > with 3 grids. I am not sure this is good neither.. > > Sorry for all these questions but thank you very much for all your help. > > Pauline > > ----- Météo-France ----- > Dr. Pauline Martinet > Chercheur CNRM/GMEI/LISA > [email protected] > Fixe : +33 561079031 > Site web: www.sites.google.com/site/martinetpauline31 > <https://www.sites.google.com/site/martinetpauline31/> > > ------------------------------------------------------------------------ > *De: *"Ole Martin Christensen" <[email protected]> > *À: *"Pauline Martinet" <[email protected]>, [email protected] > *Envoyé: *Mardi 19 Mai 2015 10:09:32 > *Objet: *RE: monochromatic pencil beam calculation > > What frequency grid are you running on in the two cases? If you have > sensor_do and backend_do your output frequencies will be determined by > you instrument backend, while if you have sensor_do = false it will be > given by f_grid. > > Could you attach your Q file? > > Ole Martin > ------------------------------------------------------------------------ > *From:* [email protected] [[email protected]] on > behalf of Pauline Martinet [[email protected]] > *Sent:* Tuesday, May 19, 2015 8:50 AM > *To:* [email protected] > *Subject:* [Qpack] monochromatic pencil beam calculation > > Hi everybody, > > I am used to simulate ground-based microwave spectra with qpack (22GHz > to 58 GHz). > > I normally define a double side band average but now I would like to > test my simulations with the assumption of monochromatic pencil beam. > > I keep the same qpack code and I only changed the variable Q.SENSOR_DO > to false instead of true. However I obtain unreasonable > brightness temperature in the most opaque channels of the O2 absorption > band. > > Here is the spectrum that I simulate with the double side band average: > > 37.1335 > 36.2098 > 31.8496 > 23.8967 > 21.4893 > 18.8657 > 17.9993 > 109.5801 > 151.6191 > 249.6631 > 278.5141 > 283.6000 > 283.8424 > 283.9169 > > whereas this is what I obtain with a monochromatic pencil beam calculation: > 36.9074 > 37.6239 > 36.9598 > 35.3325 > 33.2136 > 30.9684 > 28.8201 > 26.8801 > 25.1884 > 23.7449 > 22.5305 > 21.5187 > 20.6823 > 19.9959 > > I obtain 19K instead of 283 K for the most opaque channels, this is > weird (the last 7 channels). > > Does anyone see what the problem is, I probably did not define all the > variables needed, I just turned out the SENSOR_DO variable.. > > Thank you very much for your help. > > Best regards, > > Pauline > > ----- Météo-France ----- > Dr. Pauline Martinet > Chercheur CNRM/GMEI/LISA > [email protected] > Fixe : +33 561079031 > Site web: www.sites.google.com/site/martinetpauline31 > <https://www.sites.google.com/site/martinetpauline31/> > > > > > _______________________________________________ > 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
