From: Alex Gardner <alexg_at_nyahnyahspammersnyahnyah>

Date: Wed, 3 May 2006 14:57:55 -0600

Date: Wed, 3 May 2006 14:57:55 -0600

Thanks Adam,

I have 2 more questions:

When I constrain my 2-D field to between 60 and 90 deg N ("(i,{60:90},:)" I

get output for between 1-5 deg N. Any clue why this might be? I'm using NCEP

netCDFs

Instead of printing the output to the screen, is there a way to have each

loop's output added to a text file?

Cheers,

Alex

My Scrip now looks like this:

begin

;

tend = 24

;

a = addfile("$NCARG_ROOT/netcdf/hgt.2002.nc","r")

hgt=a->hgt(:,5,:,:)

hgtnew = (hgt*hgt_at_scale_factor) + hgt_at_add_offset

copy_VarMeta(hgt,hgtnew)

do i = 0,tend,1

x = hgtnew(i,{60:90},:)

nmin = local_min(x, True, 0.0)

print("For t = "+i+", local_min exists at "+nmin_at_yi+"N, \ "+nmin_at_xi+"E, with

a value of "+nmin_at_minval)

-----Original Message-----

From: Adam Phillips [mailto:asphilli_at_cgd.ucar.edu]

Sent: Wednesday, May 03, 2006 2:03 PM

To: Alex Gardner

Cc: ncl-talk_at_ucar.edu

Subject: Re: High Pressure Ridge Identification Algorithm?

Hi Alex,

local_min / local_max only accept 2 dimensional data:

http://www.ncl.ucar.edu/Document/Functions/Built-in/local_min.shtml

As you have 3D data, you need to put in a do loop for the time dimension:

t = x&time

do gg = 0,dimsizes(t)-1

nmin = local_min(x(gg,:,:), True, delta)

print("For t = "+t(gg)+", local_min exists at "+nmin_at_yi+"N, \

"+nmin_at_xi+"E, with a value of "+nmin_at_minval)

end do

Adam

Alex Gardner wrote:

*> Thanks again Dennis, you've been a great help.
*

*>
*

*> I've tired running the scrip but I keep getting the error message:
*

*>
*

*> "Fatal: Number of dimensions in parameter (0) of (local_min) is (3), (2)
*

*> dimensions were expected"
*

*>
*

*> The scrip I have so for is:
*

*>
*

*> a = addfile("$NCARG_ROOT/netcdf/hgt.2002.nc","r")
*

*> x=a->hgt(:,5,{60:},:)
*

*>
*

*> t = x&time
*

*> ntim = dimsizes(t)
*

*>
*

*> delta = 0. ; user specified
*

*> nmin = local_min(x, True, delta)
*

*>
*

*> ncol = 4
*

*> data = new ( (/ntim,ncol/) , typeof(x) )
*

*> data(:,0) = t
*

*> data(:,1) = nmin_at_minval
*

*> data(:,2) = nmin_at_xi
*

*> data(:,3) = nmin_at_yi
*

*>
*

*> opt = True
*

*> opt_at_fout = "alexg.txt"
*

*> write_matrix( data, "f10.1,3f10.2", opt)
*

*>
*

*> end
*

*>
*

*> The problem has to do with the time component of the field "hgt".
*

Local_min

*> doesn't seem to work when all time steps are extracted.
*

*>
*

*> Do you know how can I solve this issue?
*

*>
*

*> Alex
*

*>
*

*> -----Original Message-----
*

*> From: Dennis Shea [mailto:shea_at_cgd.ucar.edu]
*

*> Sent: Tuesday, May 02, 2006 2:46 PM
*

*> To: ncl-talk_at_ucar.edu; alexg_at_ualberta.ca
*

*> Subject: RE: [ncl-talk] High Pressure Ridge Identification Algorithm?
*

*>
*

*>
*

*>>Thank you very much for the help Dennis,
*

*>>
*

*>>The min and max functions will do what I want. What I eventually want to
*

do

*>>is output the min value, lat and long for each month of a 2 year monthly
*

*>>mean netCDF file for the region North of 60 deg North. Ideally I would
*

like

*>>to run a script that could output a single txt file with the year, month,
*

*>>value, lat, and long for each month of the 24 months the netCDF. Does
*

*>
*

*> anyone
*

*>
*

*>>have a script where they have used the locmin or locmax functions with a
*

*>>netcdf file and output the results as a txt file?
*

*>>
*

*>>Any help would be greatly appreciated.
*

*>
*

*>
*

*> quick/dirty/ and untested
*

*>
*

*> f = addfile (... , "r")
*

*> ; read data nort of 60
*

*> x = f->X(:,{60:},:) ; x(time,lat,lon) => (24,:,:)
*

*> t = x&time
*

*> ntim = dimsizes(t)
*

*>
*

*> delta = ... ; user specified
*

*> nmin = local_min(x, True, delta)
*

*> ; ????
*

*> ncol = 4
*

*> data = new ( (/ntim,ncol/) , typeof(x) )
*

*> data(:,0) = t
*

*> data(:,1) = nmin_at_minval
*

*> data(:,2) = nmin_at_xi
*

*> data(:,3) = nmin_at_yi
*

*>
*

*> opt = True
*

*> opt_at_fout = "alexg.txt"
*

*> write_matrix( data, "f10.1,3f10.2", opt)
*

*>
*

*>
*

*>>
*

*>>
*

*>>-----Original Message-----
*

*>>From: Dennis Shea [mailto:shea_at_cgd.ucar.edu]
*

*>>Sent: Monday, May 01, 2006 3:35 PM
*

*>>To: ncl-talk_at_ucar.edu; alexg_at_ualberta.ca
*

*>>Subject: Re: High Pressure Ridge Identification Algorithm?
*

*>>
*

*>>
*

*>>>I know it's a long shot, but does anyone know if there is an atmospheric
*

*>>>ridge detection (from netCDF files) function that has been developed for
*

*>>>NCL? I'm looking to develop statistics on ridging event over a particular
*

*>>>region and was hoping that maybe someone has done similar work.
*

*>>>_______________________________________________
*

*>>
*

*>>I know of no ready made software.
*

*>>
*

*>>---
*

*>>Having said that ...
*

*>>
*

*>>What do you mean by "atmospheric ridge detection"?
*

*>>
*

*>>Are you talking about atmospheric "blocks" ?
*

*>>ie: blocking highs , blocking patterns
*

*>>
*

*>>---
*

*>>There are functions that can automate detection
*

*>>of local min and max of 2D fileds
*

*>>
*

*>>
*

*>>http://www.ncl.ucar.edu/Document/Functions/Built-in/local_max.shtml
*

*>>
*

*>>An example is at:
*

*>>http://www.ncl.ucar.edu/Applications/minmax.shtml
*

*>>
*

*>>good luck
*

*>>
*

*>
*

*>
*

*>
*

*> _______________________________________________
*

*> ncl-talk mailing list
*

*> ncl-talk_at_ucar.edu
*

*> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
*

-- -------------------------------------------------------------- Adam Phillips asphilli_at_ucar.edu National Center for Atmospheric Research tel: (303) 497-1726 ESSL/CGD/CAS fax: (303) 497-1333 P.O. Box 3000 Boulder, CO 80307-3000 http://www.cgd.ucar.edu/cas/asphilli _______________________________________________ ncl-talk mailing list ncl-talk_at_ucar.edu http://mailman.ucar.edu/mailman/listinfo/ncl-talkReceived on Wed May 03 2006 - 14:57:55 MDT

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