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[ferret_users] Lesson, be careful with data only defined above a surface Re: [ferret_users] How to project 3D data onto an arbitrary 2D surface?

Thanks to Steve's suggestion to plot the fields in the YZ plane, I identified the problem as the field I was projecting was only defined above the surface. So when downscaling model output to a surface, check that the field fully intersects the surface.


Lev Tarasov -   Dept of Physics and Physical Oceanography,
		Memorial University of Newfoundland.
                email: lev@xxxxxx
		Tel (709)-737-2675
		Fax (709)-737-8739

On Wed, 15 Apr 2009, Steve Hankin wrote:

At a glance it looks correct. The trick may be to visually inspect each of the fields to spot the problem. For example, if Z[g=Thz] and HSFC were in different units? The checkerboard that you're describing would be consistent with the idea that the zeroh and kernel fields weren't "smooth". You should be able to see this using the LIST command. Pick a fixed X, for example, and LIST the kernel field in the YZ plane.

If this leads you to an answer, please report it to the email group to close the question.

  - Steve

Lev Tarasov wrote:
I have a 4D temperature field (TFIELD below), and I want to project it onto a surface topography defined by HSFC(i,j)

name title I J K L LEV level (-999 is surface) 1:8 ... ... ... HSFC Surface topography 1:128 1:64 ... 1:12 TFIELD Level temperature 1:128 1:64 1:8 1:12 HFIELD Level altitude 1:128 1:64 1:8 1:12

Finding the closest analogue in the FAQ, I tried used @WEQ, but this did not work (the surface temperature turned into a checkerboard of discontinuous values). Specifically, I did the following:

1) transform from native pressure levels to a height grid:

define AXIS/Z=-50:5500:50 /UNIT=meters zha
!plots of this looked good

2) project onto HSFC surface height field:

set mode interp
let zeroh=Z[g=Thz]-HSFC
LET kernel = zeroh[Z=@WEQ:0]
LET integrand = kernel*Thz
Let Ts=integrand[Z=@SUM]
!plots of Ts were nuts

What's the simplest way to do this correctly?



Lev Tarasov -   Dept of Physics and Physical Oceanography,
        Memorial University of Newfoundland.
                email: lev@xxxxxxxxxxxxxx

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