[arts-users] Tretyakov 2005 O2 absorption model in ARTS

[Fox, Stuart]

Hi,

I have a question about the implementation of the Treyakov 2005 O2 absorption 
model in ARTS (O2-TRE05). Looking at the source code the "a4" 
(temperature-dependence of linewidth) parameter for the lines between 368 and 
834GHz is set to 0.6, but in the Tretyakov paper it suggests a4=0 (in the 
paragraph following equation 16). Is there a reason for this difference? The 
0.6 value seems to be what is in MPM93 for these lines.

Thanks,

Stuart


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Re: [arts-users] arts_users.mi Digest, Vol 53, Issue 1

[Fox, Stuart]

Hi Renish/Stefan,

Looking at the controlfile Stefan recommends I have a couple of 
concerns/questions. Firstly, it looks to me that the Oxygen absorption set-up 
is using line parameters from the catalog file (which I'm assuming is 
HITRAN-2012?), but does not have any line mixing. I would expect this to lead 
to problems in the 50-60GHz oxygen band and have an impact out into the 89GHz 
window region. My understanding was that it was simplest to use the "O2-TRE05" 
complete absorption model for oxygen which does include the line mixing effects?

The water vapour set-up is probably fine, although my preference is to use the 
values from the AER catalog which has a couple of tweaks to better fit some 
atmospheric observations. I think the recent releases are almost the same as 
HITRAN-2016, but maybe not HITRAN-2012? Recent versions of ARTS also have the 
CKDMT320 continuum (courtesy of Emma Turner) and I've found that seems to give 
a reasonable match to much of our airborne data.

Regards,

Stuart

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Today's Topics:

   1. Choosing the right Continua models/spectroscopy data
  (Thomas,Renish)
   2. Re: Choosing the right Continua models/spectroscopy   data
  (Stefan Buehler)


--

Message: 1
Date: Thu, 12 Nov 2020 04:13:56 +
From: "Thomas,Renish" 
To: "arts_users.mi@lists.uni-hamburg.de"

Subject: [arts-users] Choosing the right Continua models/spectroscopy
data
Message-ID:



Content-Type: text/plain; charset="iso-8859-1"


Hi Everyone,

I had a question about selecting the best Continua models/spectroscopy lines 
for the most accurate simulation results.

My main species of interest is "H2O" and I am simulating an airborne sensor. 
The difference in brightness temperatures when I use the "H2O-PWR98" vs. "H2O" 
lines from the Perrin database along with the PWR98 model is greater than about 
10 degrees around the 183 GHz water vapor lines.

So, my question is, what is the best strategy on choosing the continua models 
and spectroscopic data around the absorption lines and in the window region 
(Away from absorption lines).

My region of interest is 50-300 GHz.

Also, what are the recommended spectroscopic lines and for what applications 
are they most suited for. Example : Perrins, HITRAN.

Cheers,
Renish

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Message: 2
Date: Thu, 12 Nov 2020 09:58:47 +0100
From: "Stefan Buehler" 
To: "Thomas,Renish" 
Cc: "arts_users.mi@lists.uni-hamburg.de"

Subject: Re: [arts-users] Choosing the right Continua
models/spectroscopy data
Message-ID: <62af22b7-302e-4e9f-a067-1f586d683...@uni-hamburg.de>
Content-Type: text/plain; charset="UTF-8"; format=flowed

Dear Renish,

for microwave water vapor instruments I would recommend the settings from 
controlfiles/instruments/metmm (in the ARTS distro), which were developed by 
Alex Bobryshev and used for this paper:

Bobryshev, O., S. A. Buehler, V. O. John, M. Brath, and H. Brogniez (2018), Is 
there really a closure gap between 183.31 GHz satellite passive microwave and 
in-situ radiosonde water vapor measurements?, IEEE T. Geosci. Remote, 56(5), 
2904?2910, doi:10.1109/TGRS.2017.2786548.

Best wishes,

Stefan

On 12 Nov 2020, at 5:13, Thomas,Renish wrote:

> Hi Everyone,
>
> I had a question about selecting the best Continua models/spectroscopy 
> lines for the most accurate simulation results.
>
> My main species of interest is "H2O" and I am simulating an airborne 
> sensor. The difference in brightness temperatures when I use the 
> "H2O-PWR98" vs. "H2O" lines from the Perrin database along with the
> PWR98 model is greater than about 10 degrees around the 183 GHz water 
> vapor lines.
>
> So, my question is, what is the best strategy on choosing the continua 
> models and spectroscopic data around the absorption lines and in the 
> 

Re: [arts-users] arts_users.mi Digest, Vol 52, Issue 6

[Fox, Stuart]

Hi Thomas, 

Yes, you'd expect the first-order difference between the two to be given by 
hv/2k, which is 4.8K at 200GHz. It will reduce slightly at very low brightness 
temperatures when the next-order term becomes more significant. There's a clear 
explanation in Han, Y. & Westwater, E. R. Analysis and improvement of tipping 
calibration for ground-based microwave radiometers IEEE Transactions on 
Geoscience and Remote Sensing, IEEE, 2000, 38, 1260-1276

In answer to the question of which one you should use - it depends on which one 
the instrument you are simulating is supposed to measure. Does its calibration 
process use the thermodynamic temperatures of its calibration loads, or does it 
convert them into a RJBT first?

Stuart

-Original Message-
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arts_users.mi-requ...@lists.uni-hamburg.de
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Today's Topics:

   1. RJBT vs PlanckBT units (Thomas,Renish)
   2. Re: RJBT vs PlanckBT units (Patrick Eriksson)


--

Message: 1
Date: Wed, 28 Oct 2020 15:36:41 +
From: "Thomas,Renish" 
To: "arts_users.mi@lists.uni-hamburg.de"

Subject: [arts-users] RJBT vs PlanckBT units
Message-ID:



Content-Type: text/plain; charset="iso-8859-1"

Hi Everyone,

I had a question about when to use RJBT vs PlanckBT for "iy unit", to get 
observed brightness temperatures.

I assume the difference between using the two methods should be very minimal in 
the microwave region. In some situations, especially looking through a long 
path through the atmosphere, I get about 2 - 3 K of difference in the 
200-300GHz range. Is this expected.

Cheers,
Renish
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Message: 2
Date: Wed, 28 Oct 2020 18:28:56 +0100
From: Patrick Eriksson 
To: "Thomas,Renish" ,
"arts_users.mi@lists.uni-hamburg.de"

Subject: Re: [arts-users] RJBT vs PlanckBT units
Message-ID: 
Content-Type: text/plain; charset="utf-8"

Hi Thomas,

That sounds correct. That is the expected difference, if my memory is correct.

To get insignificant differences you have to below about 30 GHz.

Bye,

Patrick

"Thomas,Renish"  skrev: (28 oktober 2020 16:36:41 
CET)
>Hi Everyone,
>
>I had a question about when to use RJBT vs PlanckBT for "iy unit", to 
>get observed brightness temperatures.
>
>I assume the difference between using the two methods should be very 
>minimal in the microwave region. In some situations, especially looking 
>through a long path through the atmosphere, I get about 2 - 3 K of 
>difference in the 200-300GHz range. Is this expected.
>
>Cheers,
>Renish
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Re: [arts-users] FASTEM in ARTS

[Fox, Stuart]

Thanks – that works fine.

Stuart

From: Richard Larsson 
Sent: 08 November 2018 17:01
To: Fox, Stuart 
Cc: arts users mi 
Subject: Re: [arts-users] FASTEM in ARTS

Hi Stuart,

A development model problem.  I am not sure this will solve your issues 
completely, but can you try adding SurfaceDummy at the start of your 
iy_surface_agenda?

The new variables you are seeing are part of a method Patrick is working on for 
calculating the Jacobian of surface features.  SurfaceDummy exists as a method 
to ignore said feature and have ARTS work as before.

See line 180 in controlfiles/general/agendas.arts for an example.  Probably, 
ARTS-2.3.638 did not have said line because the feature is new since 
ARTS-2-3-1010.

With hope,
//Richard

Den tors 8 nov. 2018 kl 17:40 skrev Fox, Stuart 
mailto:stuart@metoffice.gov.uk>>:
I’m currently trying to use the ARTS version of FASTEM via iySurfaceFastem in 
iy_surface_agenda. This used to work, but on the latest version of the ARTS 
trunk (2.3.1146) it fails with:
Run-time error in method: AgendaSet
The agenda iy_surface_agenda must generate the output WSV dsurface_rmatrix_dx,
but it does not. It only generates:
diy_dx
iy
auto_iySurfaceFastem_gin3_fastem_version

The section of my controlfile that sets the surface is:
NumericCreate(wind_speed)
NumericCreate(salinity)
NumericCreate(wind_dir)
ReadXML(wind_speed,"surface_wind_speed.xml")
ReadXML(wind_dir, "surface_wind_dir.xml")
ReadXML(salinity, "surface_salinity.xml")
AgendaSet(iy_surface_agenda){
iySurfaceFastem(salinity=salinity, wind_speed=wind_speed, 
wind_direction=wind_dir)
}

This used to work (certainly it worked at version 2.3.638), so I’m guessing 
something has changed (it looks like it’s related to calculating surface 
jacobians). Is this a bug, or do I need to add something extra to 
iy_surface_agenda to calculate the required quantities?

Regards,

Stuart

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[arts-users] FASTEM in ARTS

[Fox, Stuart]

I'm currently trying to use the ARTS version of FASTEM via iySurfaceFastem in 
iy_surface_agenda. This used to work, but on the latest version of the ARTS 
trunk (2.3.1146) it fails with:
Run-time error in method: AgendaSet
The agenda iy_surface_agenda must generate the output WSV dsurface_rmatrix_dx,
but it does not. It only generates:
diy_dx
iy
auto_iySurfaceFastem_gin3_fastem_version

The section of my controlfile that sets the surface is:
NumericCreate(wind_speed)
NumericCreate(salinity)
NumericCreate(wind_dir)
ReadXML(wind_speed,"surface_wind_speed.xml")
ReadXML(wind_dir, "surface_wind_dir.xml")
ReadXML(salinity, "surface_salinity.xml")
AgendaSet(iy_surface_agenda){
iySurfaceFastem(salinity=salinity, wind_speed=wind_speed, 
wind_direction=wind_dir)
}

This used to work (certainly it worked at version 2.3.638), so I'm guessing 
something has changed (it looks like it's related to calculating surface 
jacobians). Is this a bug, or do I need to add something extra to 
iy_surface_agenda to calculate the required quantities?

Regards,

Stuart

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[arts-users] Modelling polarisation for aircraft-based along-track scanners

[Fox, Stuart]

Hi,

Is it possible yet to properly handle the sensor polarisation response in ARTS 
for aircraft-based along-track scanners (ISMAR and MARSS) where the detected 
polarisation rotates with scan angle, for arbitrary platform orientations? I 
think it is possible to use the MetMM interface for wings-level flight - has 
anything been developed yet that works for non-zero aircraft roll angles, and 
if so then how do I provide the required inputs? Or is it best to just 
calculate H & V (or I and Q) responses and combine them myself afterwards?

Thanks,

Stuart

Dr Stuart Fox  Radiation Research Scientist
Met Office FitzRoy Road  Exeter  Devon  EX1 3PB  United Kingdom
Tel: +44 (0)1392 885197  Fax: +44 (0)1392 885681
Email: stuart@metoffice.gov.uk  Website: www.metoffice.gov.uk

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