[OpenMadrigal-developers] F10.7 Multiday average proposal

Fri Oct 20 15:36:24 EDT 2006

Yes, that's what I intended.  It seems the CEDAR definition really never 
covered the close-to-realtime (at least < 40 day) case, so I figured we 
could document that and use it to fill in the gap.  As it is now, we 
have a 'missing' value in the < 40 day case.

----
phil

John Holt wrote:
> I agree with Sunrong's reasoning but, unfortunately, the acausal
> definition of F10.7bar is now the one in common use. Phil's definition,
> as I understand it, retains that definition for all but the most recent
> 40 days and converges on the common definition after 40 days. The only
> CEDAR definiton I could find is not explicit.
> 
> John
> 
>> Date: Fri, 20 Oct 2006 15:07:17 -0400
>> From: Shunrong Zhang <shunrong at haystack.mit.edu>
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>> If we totally redefine Fbar to be for the last 81 days, that is fine; 
>> but I think what Phil suggested was "for any day less than 40 days in 
>> the past, we  calculate FBAR as an average over the most recent 81 days. 
>> " That sounds to me that you still use the old definition for any day 
>> greater than day 40 days in the past. I wanted to say that there should 
>> not be two definitions for one parameter. From modeling point of view, I 
>> agree with John that "ending with the day of interest will tend to give 
>> a somewhat better prediction". That was why I suggested my option (2) 
>> for a new F107 index that is an average over the past 81 days and is 
>> always available.
>>
>> Shunrong
>>
>>
>> John Holt wrote:
>>> Phil's suggestion seems reasonable. In the context of a model, the
>>> definition of F10.7bar as a centered average is an absurdity,
>>> obviously. In the "old" days we always used the 81 days ending with the
>>> day of interest, but at some point it apparently became more common to
>>> forget causality and use a centered average (I have seen 27 days, 54
>>> days, 81 days 90 days and one year) and a variety of filter functions
>>> causal and not.  Unfortunately, in my view, causal filters fell out of
>>> favor.  Had they not, we would not have had this problem and would have
>>> been consistent with the laws of physics as well, which is no small
>>> thing. I suspect, by the way, that using the 81 days ending with the
>>> day of interest will tend to give a somewhat better prediction than
>>> using a centered average, even though the model was computed using a
>>> centered average.
>>>
>>> John
>>>
>>> ________________________________________________________________________
>>> |                                                                      |
>>> | John M. Holt                         tel:   781-981-5625             |
>>> | Principal Research Scientist         fax:   781-981-5766             |
>>> | MIT Haystack Observatory             email: jmh at haystack.mit.edu     |
>>> | Route 40                             WWW:   http://www.haystack.edu/ |
>>> | Westford, MA 01886                                                   |
>>> | USA                                                                  |
>>> |________________ Ni h-eibhneas gan chlainn domhnaill _________________|
>>>
>>>
>>>   
>>>> Date: Fri, 20 Oct 2006 11:53:15 -0400
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>>>> Subject: [OpenMadrigal-developers] F10.7 Multiday average proposal
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>>>> Phil Erickson has suggested we modify out definition of the F10.7 
>>>> Multiday average (FBAR).  Right now this is an 81 day average, where the 
>>>> 81 days the center day, 40 days in the past, and 40 days in the future.  
>>>> The problem with this definition is that this parameter is never 
>>>> available for any day less than 40 days in the past.  For example, since 
>>>> MSIS uses FBAR as an input, this means that MSIS also cannot be run for 
>>>> any day less than 40 days in the past. 
>>>>
>>>> Phil has suggested that for any day less than 40 days in the past, we 
>>>> calculate FBAR as an average over the most recent 81 days.  From the 
>>>> Madrigal point-of-view, this means that every time we reload geophysical 
>>>> data, the FBAR values for the latest 40 days might change slightly.  At 
>>>> present, FBAR is not loaded into Madrigal for days less than 40 days ago.
>>>>
>>>> We would document this FBAR definition on the Madrigal help pages.  Any 
>>>> thoughts?
>>>>
>>>> Bill Rideout
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>>
>> -- 
>>
>> _____________________________________________________________
>>  Shunrong Zhang  (shunrong at haystack.mit.edu)
>>  http://www.haystack.mit.edu/~shunrong/
>>  MIT Haystack Observatory, Route 40, Westford, MA 01886, USA
>>  Phone: 781-981-5725 FAX: 781-981-5766
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