Dear everybody, 

Sorry for all my questions these last days, I have two projects with Qpack and 
I have to deal with both of them at the same time. 

I am reviewing an article using Qpack but the reviewer asks me to 
simultaneously retrieve the liquid water path (LWP) with the temperature. 

I would like to modify the routine oem.m of Qpack to minimize the cost function 
with respect to the liquid water path and not the liquid water content profile. 

I have some ideas in mind: when I am in the oem.m routine like: 

1) Modify the B matrix to only have one value for LWP instead of background 
errors for the whole liquid water content profile 
2) After the computation of the Jacobians for the liquid water content profile, 
change it to only have one value of Jacobians (delta TB with 
respect to LWP) 
3) after finding the xstep that minimizes the cost function, go back from the 
LWP increment to an increment on the whole liquid water content profile. 
Then, the new x profile is found, no modification for the convergence test 
should be done. 

I do not know if it is more complicated then that as I do not know well how the 
whole Qpack is coded, I mainly know this oem.m routine. 

Does anyone have ever done such a modification ? If not, does anyone could help 
me doing it alone ? 
and do you think it would take a lot of time. I only have 4 weeks to send back 
my reviews. If it sounds too complicated, I will try 
to explain to the reviewer this is not possible with the current version of 
Qpack. 

Thank you very much in advance ! 

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 

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