[ncl-talk] cross_corr_query
Adam Phillips
asphilli at ucar.edu
Fri Sep 9 10:14:35 MDT 2016
Hi Kunal,
Your use of esccr is correct as far as I can tell. It matches up with
example #2 on the esccr documentation site:
http://www.ncl.ucar.edu/Document/Functions/Built-in/esccr.shtml
Adam
On Fri, Sep 9, 2016 at 1:28 AM, Kunal Bali <kunal.bali9 at gmail.com> wrote:
>
> I have the data over the central arabian sea with the time steps = 31.
>
> With the given script, could you please let me know am I doing the
> corss-correlation in a wright way
>
> ;*************************************************
> ; corel_3.ncl
> ;
> ; Concepts illustrated:
> ; - Calculating a two-dimensional correlation in time
> ; - Reordering an array
> ; - Copying attributes from one variable to another
> ; - Copying coordinate arrays from one variable to another
> ;
> ;************************************************
> ;
> ; These files are loaded by default in NCL V6.2.0 and newer
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
> begin
> ;************************************************
> ; open file and read in variable
> ;***********************************************
> in1 = addfile("/media/Local Disk/NPL2/cross_corr_spatial/var1.nc","r")
> in2 = addfile("/media/Local Disk/NPL2/cross_corr_spatial/var2.nc","r")
>
>
> tmp1 = in1->DUD
> tmp2 = in2->SRT
> ;************************************************
> ; reorder to get time as right most dimension
> ;***********************************************
> ts1 = tmp1(latitude|:,longitude|:,time|:)
> ts2 = tmp2(latitude|:,longitude|:,time|:)
> ;************************************************
> ; calculate cross correlations
> ;************************************************
> maxlag = 3 ; set lag
> ; note, the max lag should not be more than N/4
>
> ccr = esccr(ts1,ts2,maxlag) ; calc cross correlations
>
> ; copy meta data and coordinate variables using contributed functions
> copy_VarAtts(ts1, ccr)
> copy_VarCoords_1(ts2,ccr)
> ;************************************************
> ; plot the correlations
> ;************************************************
> ;************************************************
> ;---Open workstation and change color map
> wks_type = "png"
> wks = gsn_open_wks(wks_type, "CCR_2_lag3")
> ;************************************************
>
>
> res = True ; make plot mods
> res at gsnLeftString = ""
> res at gsnRightString = ""
> res at gsnAddCyclic = False
> res at cnFillOn = True ; turn on color
> res at cnFillPalette = "BlWhRe" ; set color map
>
> res at cnLinesOn = False ; turn off contour lines
> res at cnLevelSelectionMode = "ManualLevels" ; manually set cn levels
> res at cnMinLevelValF = -1. ; min level
> res at cnMaxLevelValF = 1. ; max level
> res at cnLevelSpacingF = .1 ; contour level spacing
>
> lag = 3
> res at tiMainString = "Correlations at lag "+lag
>
> res at mpMinLonF = 59.8
> res at mpMaxLonF = 69.8
> res at mpMinLatF = 16.5
> res at mpMaxLatF = 25.0
>
> plot = gsn_csm_contour_map(wks,ccr(:,:,lag),res)
> ;************************************************
> end
>
>
>
> Kunal Bali
> Research Scholar
> Radio & Atmospheric Science Division
> CSIR - National Physical Laboratory
> New Delhi - 110012
> India
>
>
>
>
>
> On Fri, Sep 9, 2016 at 12:28 PM, Will Hobbs <will.hobbs at utas.edu.au>
> wrote:
>
>> Kunal
>>
>>
>>
>> At least one of the data points in the arrays that you are correlating
>> has every single value as ‘missing’ or the same value throughout. This
>> usually occurs if your data includes some masked regions, e.g. ocean data
>> with a spatial domain that includes land.
>>
>>
>>
>> Another possible valid condition would be precipitation data where one or
>> more data points has been in drought for the entire time period, i.e. P = 0
>> throughout
>>
>>
>>
>> If you’re expecting you input data to include masked areas or similar
>> physical conditions then it’s probably nothing to worry about (although
>> that doesn’t mean you shouldn’t check). If you’re not expecting any missing
>> values in your data then you may have a problem with your input arrays –
>> but that’s not really an NCL problem.
>>
>>
>>
>> Will
>>
>>
>>
>>
>>
>>
>>
>> *From: *<ncl-talk-bounces at ucar.edu> on behalf of Kunal Bali <
>> kunal.bali9 at gmail.com>
>> *Date: *Friday, 9 September 2016 at 4:46 PM
>> *To: *"ncl-talk at ucar.edu" <ncl-talk at ucar.edu>
>> *Subject: *[ncl-talk] cross_corr_query
>>
>>
>>
>> Dear NCL users,
>>
>> I am trying to plot the cross-correlation map. While doing this, I have
>> baeen facing one error
>>
>> warning:esccr: Non-fatal conditions encountered: all missing or constant
>> values
>>
>> Could anyone please let me know, how to fix it.
>>
>> Regards
>>
>> Kunal Bali
>>
>>
>>
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>
>
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--
Adam Phillips
Associate Scientist, Climate and Global Dynamics Laboratory, NCAR
www.cgd.ucar.edu/staff/asphilli/ 303-497-1726
<http://www.cgd.ucar.edu/staff/asphilli>
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