[MITgcm-support] Values about adjoint ADJ* results

[Peng Zhan]

Hi Matthew,

I found the file of "costfinal" gives 25.60, which is reasonable for a
daily averaged SST over a box.
This suggests the cost function is defined without unknown weights that may
change the scale, right?

If yes, then we still need to figure out where is the 10^-6 from. Any
comment?

Thanks, Peng

On Wed, May 3, 2017 at 7:50 PM, Matthew Mazloff <mmazloff at ucsd.edu> wrote:

> ps> Though its an average the costfunction will accumulate. So I think it
> should be divided by secs per day and number of boxes in the average,
> making 10^-7 sounds about right!
>
>
>
>
> On May 3, 2017, at 9:37 AM, Matthew Mazloff <mmazloff at ucsd.EDU
> <mmazloff at ucsd.edu>> wrote:
>
> Hello
>
> Essentially yes, though weighted by your cost function design. So ADJtheta
> will have volume and timestep weigthing in it.
>
> Its linear so your average is essentially the sum of grid cell
> costfunctions. Try letting your costfunction be SST for one grid cell and
> one time step and figuring out the weighting from that.
>
> Matt
>
>
> On May 3, 2017, at 9:29 AM, Peng Zhan <peng.zhan at kaust.edu.sa> wrote:
>
> Dear all,
>
> I am doing the adjoint sensitivity analysis, but get confused about the
> values' physical meaning in the ADJ* results.
>
> For instance, the cost function J is defined using daily average SST over
> a box, the ADJ* results are about 10^-7 to 10^-6 in magnitude.
>
> 1. Is the surface ADJtheta the sensitivity to SST it self?
> 2. If yes, the sum of ADJtheta over the box right before the target day
> should be close to 1?
>
>
> Thanks in advance, Peng
>
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-- 

Peng ZHAN

______________________________
PhD Candidate
Earth Science & Engineering (ErSE)
King Abdullah University of Science and Technology (KAUST)
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Mobile: +966 544701621
* <peng.zhan at kaust.edu.sa>*

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