Re: Ridges and troughs

Hi Patrick,

I have a couple of subroutines I use to draw objective trough and jet axes
in NCL. They were designed for African easterly waves, but you can change
the code to do ridges as well pretty easily. It defines troughs and ridges
by splitting the wind filed into its shear and curvature components.

I haven't had time to fully integrate it into NCL so it's a f90 routine that
you call from inside an NCL script and still has a few bugs (like hard-coded
fill values, regular grids only) that are on my long list of things to sort
out. It may take some tweaking with the sensitivities and various
thresholds, but in principle it's pretty simple and you're welcome to make
improvements.

I've got a webpage with the source code and background info:

http://www.atmos.albany.edu/student/gareth/source.htm

I use the code to generate real-time objective diagnostics from GFS data:

http://www.atmos.albany.edu/student/gareth/plots.html

Cheers,

Gareth.

On Tue, Apr 14, 2009 at 5:58 AM, Patrick Reuter <preuter64@yahoo.de> wrote:

> Dear,
>
> please let me plug to this topic:
>
> Are there any NCL scripts available that automatically draw those
> front lines from gridded data, such as GFS or WRF ?
>
> This would be very helpful.
>
> Thanks in advance
> Patrick
>
>
> "Correia, James" <james.correia@pnl.gov> a écrit :
>
> > I believe you want to draw fronts:
> > http://www.ncl.ucar.edu/Document/Functions/Built-in/wmdrft.shtml
> > Good luck
> > jimmyc
> >
> >
> > On 4/13/09 8:14 AM, "Michel dos Santos Mesquita"
> > <Michel.Mesquita@bjerknes.uib.no> wrote:
> >
> >> Hi,
> >>
> >> I am working on a plot where I need to draw a 'ridge' line (MSLP
> >> chart). In the book "Weather Analysis" page 32 (Djuric), 'ridges' are
> >> drawn as kinked lines and 'troughs' as wavy lines. Is there a way to
> >> do that using gsn_add_polyline?
> >>
> >> Another question: I need to make a line illustrating the flow of air
> >> in an MSLP chart. This is not a straight line. If I use
> >> gsn_add_polyline, the curve I am trying to draw looks more like a
> >> 'step function' than a smooth curve. When I try to use a bicubic
> >> spline, I get an error saying that I don't have enough input data:
> >> "SPLCC or SPLCW - SUPRLS failure". And if I use 'ftcurvs', I get error
> >> 4, which means that my lines are not increasing. This is because my
> >> latitude and longitude vary (increasing/decreasing). Is there a way to
> >> draw such curves in NCL?
> >>
> >> I thank you so much in advance!
> >>
> >> Kindest regards,
> >>
> >> Michel
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Received on Tue Apr 14 08:10:35 2009