[Cosmic_announce] (no subject)

[Lidia Cucurull]

Dear Doug,

Please, do NOT make any change in the operational data stream until  
the operational weather services have time to test the impact of the  
changes. I believe it will take more than a couple of weeks.

Thanks
Lidia

On Mar 20, 2009, at 1:36 PM, Doug Hunt wrote:

> Greetings:
>
> Recently it was found (thanks to Christian Marquardt from EUMETSAT)
> that the filtering used in our inversion software produces a bias
> in retrieved bending angles. This bias is seen mainly above 10-20km
> and its magnitude is of order of 0.1-0.2%. This bias is due to second
> derivative of the excess phase as a function of time. This bias
> propagates into the retrieved refractivity and, subsequently, into
> other retrieved profiles. We will be replacing the filtering which
> reduces the bias by several decimal orders of magnitude.
>
> Concurrently we will be making another change by fixing the transition
> height between geometric optics and radio holographic processings
> to ~20 km (currently this height is determined individually for each
> occultation and can be anywhere between ~10 and ~20 km). The purpose
> of this change is to aid studies of the structure of tropopause by
> providing the vertical resolution of about ~0.1 km below 20 km for
> all occultations.
>
> Both these changes are not yet included in our real time processing.
> The data, BUFR files for November-December 2008, processed with
> these changes are available at:
>
> http://www.cosmic.ucar.edu/~dhunt/BUFR_with_new_filtering/
>
> for testing in data assimilation systems. We would appreciate your
> feedback. We would like to include these changes in our real time
> processing in about 2 weeks. Later, we will re-process all our data
> for all missions.
>
> Best Regards,
>
>   Doug Hunt
>
> dhunt at ucar.edu
> Software Engineer IV
> UCAR - COSMIC, Tel. (303) 497-2611
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