Re: [arts-users] Tropospheric continuum retrieval in ARTS

[Patrick Eriksson]

Eric,

(1998)). The values of the poly_order=0 are now quite small (mostly 
lower than 0.1K), however, I still only get positive values. Is that 
something that could be expected from the way the function 
"retrievalAddPolyfit" works maybe ?


No, there is nothing that promotes positive values. But you now get so 
small values that nothing to worry about.
You get very consistent values for poly_order 1 and 2, despite that the 
tropospheric opacity varies quite a bit. That should be an indication on 
that receiver is stable and the baseline+tropospheric part of the 
retrievals is working well.



Would you have any tips on how to implement the retrieval of a single 
scaling parameter for a full water vapor profile ? I believe this is 
more or less what the CONTABS_DO parameter was implementing according to 
the first Qpack documentation ?


This you do by setting the retrieval grid to have a single point (e.g. 
500 hPa) and set the corresponding covariance matrix to have size 1x1. A 
suitable value for it is maybe 1 (meaning a 100% uncertainty at all 
altitudes, fully correlated).


Bye,

Patrick
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Re: [arts-users] Query on ARTs cross section files

[Oliver Lemke]

Hi Songyan,

Great to hear that you're working with CFCs. Your question comes at an (almost) 
perfect time. :-)

We are right now working on bringing all the pieces together to provide an 
improved implementation of the cross section model in the development version 
of ARTS. It should be available within the next two weeks.

The required XML input files for the new model will be provided in our 
arts-xml-data package.

Since we consider the implementation in ARTS v2.4 as experimental and more as a 
proof of concept, I would recommend that you wait a couple of days until the 
new version is ready.

We would very much appreciate if you consider using the new model for your 
work. Your feedback would also be very valuable for us.

I'll keep you posted.

Cheers,
Oliver


> On 22 Jun 2021, at 09:51, Zhu, Songyan  wrote:
> 
>  
> Dear ARTs team,
>  
> My name is Songyan Zhu, a Phd student at the University of Exeter, UK.
>  
> I’m using ARTs to simulate impacts of CFCs on the climate in infra-red.
> However, ARTs v2.4 requires the cross section files in xml format, but 
> available cross sections from HITRAN are in xsc.
> So I’m wondering is there anyway I can convert the xsc files into xml or some 
> place where I can find xml cross sections?
>  
> Best, Songyan 
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[arts-users] Query on ARTs cross section files

[Zhu, Songyan]

Dear ARTs team,

My name is Songyan Zhu, a Phd student at the University of Exeter, UK.

I’m using ARTs to simulate impacts of CFCs on the climate in infra-red.
However, ARTs v2.4 requires the cross section files in xml format, but 
available cross sections from HITRAN are in xsc.
So I’m wondering is there anyway I can convert the xsc files into xml or some 
place where I can find xml cross sections?

Best, Songyan
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Re: [arts-users] Hail particles in ARTS

[Patrick Eriksson]

Enzo,

As far as I know there are no available data for such large hail particles.

How you can calculate the scattering properties depends mainly on the 
size parameter, i.e. the ratio between particle size and wavelength. 
Accordingly, it would help to know the frequencies you want to simulate.


If I guess that you want at least to cover 30 GHz, then it will be a 
challenge to use DDA if you really want to do 10 cm particles.


In any case, to get started the simplest option seems to be use Mie 
code. That is, to assume the hail to be spherical, maybe combined with 
"mixing model" to set an effective refractive index. I think there is 
some special Mie code that handles layered spheres that could be 
interesting to explore.


To give you some quick feedback.

Bye,

Patrick


On 2021-06-21 16:18, Enzo Papandrea wrote:


Hi,

we would like to simulate “hail particles" of considerable size (e.g. 5 cm and 
10 cm) using ARTS.
The properties, needed as input are not available in the ARTS distribution (the 
maximum size is 1 cm) but we read that there is the possibility to calculate 
them through some tools.

Could you please suggest which is the easiest tool we can use? Or, even better, 
is there the possibility to download already per-computed lookup tables?
Thank you for your support

Best,
Enzo.
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