Hi Patrick,

Thank you for explaining me again the use of Q.MBLOCK_ZA_GRID.

I had an error in my code as I was using Q.MBLOCK_ZA_GRID to specify the 
different viewing angles of the sensor
whereas it is related to the antenna pattern (so I assume it is in 
Q.MBLOCK_ZA_GRID where I can define the beam width of the antenna) .

I added Q.SENSOR_POS and Q.SENSOR_LOS in my code now and I changed the 
Q.MBLOCK_ZA_GRID value to 0. 

For my second question, as it is complicate to set up such a configuration, I 
will try to use my solution
about putting a very high observation error on the angles I don't want to use.

Thank you again.

Best regards,

Pauline

----- Météo-France -----
Dr. Pauline Martinet 
Chercheur CNRM/GMEI/LISA
[email protected]
Fixe : +33 561079031 
Site web: https://sites.google.com/site/martinetpauline31/                      
                                        


----- Mail original -----
De: "Patrick Eriksson" <[email protected]>
À: "MARTINET Pauline" <[email protected]>
Cc: "George P. Ford" <[email protected]>, [email protected]
Envoyé: Mercredi 10 Septembre 2014 10:18:24
Objet: Re: [Qpack] retrieval of humidity profiles with qpack and multi viewing 
angles

Hi Pauline,

> When I call arts just for forward calculations and not retrieval like
> in the qarts_demo.m file, I give all the viewing angles of the sensor
> in Q.MBLOCk_ZA_GRID if I am not wrong.

If you mean to use qarts without involving qpack, you then set 
Q.SENSOR_POS and Q.SENSOR_LOS.

Q.MBLOCK_ZA_GRID is associated with how to consider/include an antenna 
response. However, due to technical issue you can "fool" arts to provide 
several pencil beam spectra by setting Q.MBLOCK_ZA_GRID, but the 
recommended way is to use SENSOR_POS and  SENSOR_LOS.


> One last question about the retrieval with qpack. From what I
> understand, I assume this is not possible to use different viewing
> angles for the different frequencies of the sensor ?
>
> I mean, for example I would like to perform a retrieval with
> observations only in the zenith direction for the first two
> frequencies and then I would like to use a set of 10 viewing angles
> for the other frequencies of the sensor.
>
> Is it possible to do that with qpack ?

Since quite recently this is possible. We are doing something similar in 
some new Onsala retrievals. However, this is very  difficult to set up. 
You would need from me, or maybe Ole Martin can help.

So think  about how critical this is for you, and tell us if you need help.


Bye,

Patrick
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