[gradsusr] If Statements for Gridded Model Data Open GrADS
Frank Colby
Frank_Colby at uml.edu
Wed Jun 22 12:33:40 EDT 2016
Matt,
I don't think you can use the compound test in one if statement. That
is, you can do
if(NAMcape > 1500)
if(NAMcape < 2200)
NAMHail = NAMHail + 1
endif
end if
which should do what you want.
Frank
On 6/22/2016 12:11 PM, Baker, Matt (Quebec - Atlantic) wrote:
>
> Thanks Bernd and Stephen,
>
> Essentially if the CAPE, LI, and 500 mb relative humidity are within a
> certain range, I want to add to NAMHail variable (NAMHail = NAMHail +
> 1) and then display the variable with contour lines.
>
> Stephen, in my code there are already if statements for this. Is there
> something wrong with my syntax and could that be the reason GrADS
> isn’t executing in the if statement?
>
> As an example, is this statement written correctly?
>
> if (NAMcape > 1500 & NAMcape < 2200)
>
> 'NAMHail = NAMHail + 1'
>
> endif
>
> Again, NAMHail is defined by: ‘NAMHail = 0’ before the if the
> statements.
>
> Thanks for the help!
>
> Matt
>
> *From:*gradsusr-bounces at gradsusr.org
> [mailto:gradsusr-bounces at gradsusr.org] *On Behalf Of *Stephen McMillan
> *Sent:* June-22-16 12:39 PM
> *To:* GrADS Users Forum <gradsusr at gradsusr.org>
> *Subject:* Re: [gradsusr] If Statements for Gridded Model Data Open GrADS
>
> Hi Matt,
>
> In addition to Bernd's suggestion, also check out the "if" function,
> which should have come with your opengrads package as part of the
> following extension function set:
>
> http://opengrads.org/doc/udxt/libbjt/
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__opengrads.org_doc_udxt_libbjt_&d=CwMGaQ&c=lqHimbpwJeF7VTDNof4ddl8H-RbXeAdbMI2MFE1TXqA&r=6tSfNfW9eok2dvPp1qvMgNtd3pXLhNg0FMEbTXyDrbI&m=R2wE3ABOgZSkEecrNzXKCrGNBI-1ggl2FOBCoFl-0IU&s=-e8J0y0k4721djnHE87Jw9gSRHvi54JAu7Y5nLvuuxs&e=>
>
> The "if" function syntax:
>
>
> *if*(/EXPR1,OP,EXPR2,TRUE_EXPR,FALSE_EXPR/)
>
> This function compares /EXPR1/ and /EXPR2/, where 5 arguments are
> expected. if their relation is true, /TRUE_EXP/ is returned, otherwise
> expression /FALSE_EXPR/ is returned.
>
> /*OP*/
>
> One of the following: ==, =, >, <, >=, <=, !=
>
> /*EXPR2, TRUE_EXPR, FALSE_EXPR*/
>
> These can be a expression, constant or -u.
>
> I have found this function to be very useful and much easier to handle
> than using maskout and const, although there are probably cases where
> the latter is more appropriate or advisable.
>
> Stephen McMillan
>
> On Wed, Jun 22, 2016 at 9:24 AM, Baker, Matt (Quebec - Atlantic)
> <matt.baker at amecfw.com <mailto:matt.baker at amecfw.com>> wrote:
>
> Hi all,
>
> I have a question regarding Open GrADS.
>
> I’m trying to use /if statements/ for scalar model data (eg. GFS
> and NAM) over a grid and I’m wondering if it’s possible to do
> this. As an example, I’m using if statements for these parameters:
> surface based CAPE, LI, and 500 mb relative humidity to create an
> index to plot on a map. So far GrADS isn’t showing that this is
> working, however, I can plot the model data individually so I
> don’t think it’s a case of missing data.
>
> Here’s some of the code for the NAM model. Note that I define the
> variable NAMHail to equal 0 at the start of the function.
>
> if (modelNumberNAM>0)
>
> set_maps(_map,_hasNegativeNAM)
>
> 'set grads off'
>
> 'set grid off'
>
> 'set gxout contour'
>
> 'set ccolor 0'
>
> 'set clopts -1 1 0.15'
>
> 'set cint 1'
>
> 'set cthick 6'
>
> 'set clab on'
>
> 'set csmooth on'
>
> 'NAMcape = CAPEsfc.'modelNumberNAM
>
> if (NAMcape > 1500 & NAMcape < 2200)
>
> 'NAMHail = NAMHail + 1'
>
> endif
>
> if (NAMcape > 2199 & NAMcape < 3100)
>
> 'NAMHail = NAMHail + 2'
>
> endif
>
> if (NAMcape > 3099)
>
> 'NAMHail = NAMHail + 3'
>
> endif
>
> 'set lev 500'
>
> 'NAMrh500=RHprs.'modelNumberNAM
>
> if (NAMrh500 < 35)
>
> 'NAMHail = NAMHail + 3'
>
> endif
>
> if (NAMrh500 > 35 & NAMrh500 < 44)
>
> 'NAMHail = NAMHail + 1'
>
> endif
>
> endif
>
> 'set gxout contour'
>
> 'set ccolor 0'
>
> 'set clopts -1 1 0.15'
>
> 'set cint 200'
>
> 'set cthick 6'
>
> 'set clab on'
>
> 'set csmooth on'
>
> 'd NAMcape'
>
> Thanks!
>
> *Matt Baker*
>
> Meteorologist, Met-Ocean Services, Amec Foster Wheeler Environment
> & Infrastructure
>
> 133 Crosbie Road, PO Box 13216, St. John’s, NL A1B 4A5, Canada
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