[ncl-talk] (I)PV units?
Dennis Shea
shea at ucar.edu
Thu Sep 8 09:12:51 MDT 2016
Hi Kacie,
I see the issue.
As noted in the documentation:
http://www.ncl.ucar.edu/Document/Functions/Contributed/pot_vort_isobaric.shtml
"Compute potential vorticity on isobaric levels and a global rectilinear
grid."
----
After you regrid, you have a rectilinear grid. However, it is not "global."
EG:
Variable: tkReGr
Number of Dimensions: 3
Dimensions and sizes: [lv_ISBL3 | 29] x [lat | 337] x [lon | 831]
Coordinates:
lv_ISBL3: [100..1000]
lat: [ 1.. 85] <==== Regional grid
lon: [ 150..358.5] <====
The 'pot_vort_isobaric' function uses spherical harmonic functions to
calculate the required meridional and zonal gradients. The spherical
harmonic functions are "highly accurate" however they require global grids.
===
As I recall, in the summer NCL Workshop, we discussed this issue. :-)
As an exercise, I suggested that you copy and modify 'pot_vort_isobaric' to
use the 6.4.0 'grad_latlon_cfd' function to replace the spherical harmonic
gradient functions.
http://www.ncl.ucar.edu/Document/Functions/Contributed/grad_latlon_cfd.shtml
Some gradient examples are at:
http://www.ncl.ucar.edu/Applications/gradients.shtml
Actually, in your script, you have a commented line:
;load "/grid-scratch/kshourd/code/potVortCFD.ncl"
So .... it looks like you have a created a function but you did not use
it???
===
I decided to create a function 'pot_vort_isobaric_cfd'. It has slightly
different arguments.
See attached.
Likely, I will include 'pot_vort_isobaric_cfd' in the 6.4.0 release as part
of contributed.ncl
D
On Wed, Sep 7, 2016 at 12:31 PM, Kacie Shourd <Kacie.Shourd at dri.edu> wrote:
> Hi all,
>
>
>
> I am encountering some problems with my potential vorticity (PV) and
> subsequent isentropic potential vorticity calculations (IPV). The patterns
> I am getting look right, but the magnitude of the values does not make
> sense. I assume pot_vort_isobaric() function outputs in raw units rather
> than PVUs?
>
>
>
> I have checked my units/script over and over and over again, and cannot
> figure out why the values are a few orders of magnitude off. It seems as
> though maybe my pressure values are being input into the equations wrong
> (or some other variable is). The patterns of PV make sense for the event,
> but the magnitude is most certainly wrong.
>
>
>
> Any insight into what I am doing wrong or any other reasons the calculated
> PV values are coming out really large. Scripts, output, and necessary
> files to run script can be found here: ftp://pubfiles.dri.edu/pub/
> kshourd/nclTalkIPVHelp/ , and variable summaries are as follows:
>
>
>
> ---
>
> Variable: tkReGr
>
> Type: float
>
> Total Size: 32485452 bytes
>
> 8121363 values
>
> Number of Dimensions: 3
>
> Dimensions and sizes: [lv_ISBL3 | 29] x [lat | 337] x [lon | 831]
>
> Coordinates:
>
> lv_ISBL3: [100..1000]
>
> lat: [ 1.. 85]
>
> lon: [ 150..358.5]
>
> Number Of Attributes: 15
>
> sub_center : The North American Regional Reanalysis (NARR) Project
>
> center : US National Weather Service - NCEP (WMC)
>
> long_name : Temperature
>
> units : K
>
> _FillValue : 1e+20
>
> level_indicator : 100
>
> grid_number : 221
>
> parameter_table_version : 131
>
> parameter_number : 11
>
> model : North American Regional Reanalysis (NARR)
>
> forecast_time : 0
>
> forecast_time_units : hours
>
> initial_time : 09/26/2010 (18:00)
>
> remap : remapped via ESMF_regrid_with_weights: Bilinear
>
> missing_value : 1e+20
>
>
>
> ---
>
> Variable: uN
>
> Type: float
>
> Total Size: 32485452 bytes
>
> 8121363 values
>
> Number of Dimensions: 3
>
> Dimensions and sizes: [lv_ISBL3 | 29] x [lat | 337] x [lon | 831]
>
> Coordinates:
>
> lv_ISBL3: [100..1000]
>
> lat: [ 1.. 85]
>
> lon: [ 150..358.5]
>
> Number Of Attributes: 15
>
> sub_center : The North American Regional Reanalysis (NARR) Project
>
> center : US National Weather Service - NCEP (WMC)
>
> long_name : u-component of wind
>
> units : m/s
>
> _FillValue : 1e+20
>
> level_indicator : 100
>
> grid_number : 221
>
> parameter_table_version : 131
>
> parameter_number : 33
>
> model : North American Regional Reanalysis (NARR)
>
> forecast_time : 0
>
> forecast_time_units : hours
>
> initial_time : 09/26/2010 (18:00)
>
> remap : remapped via ESMF_regrid_with_weights: Bilinear
>
> missing_value : 1e+20
>
>
>
> ---
>
> Variable: vN
>
> Type: float
>
> Total Size: 32485452 bytes
>
> 8121363 values
>
> Number of Dimensions: 3
>
> Dimensions and sizes: [lv_ISBL3 | 29] x [lat | 337] x [lon | 831]
>
> Coordinates:
>
> lv_ISBL3: [100..1000]
>
> lat: [ 1.. 85]
>
> lon: [ 150..358.5]
>
> Number Of Attributes: 15
>
> sub_center : The North American Regional Reanalysis (NARR) Project
>
> center : US National Weather Service - NCEP (WMC)
>
> long_name : v-component of wind
>
> units : m/s
>
> _FillValue : 1e+20
>
> level_indicator : 100
>
> grid_number : 221
>
> parameter_table_version : 131
>
> parameter_number : 34
>
> model : North American Regional Reanalysis (NARR)
>
> forecast_time : 0
>
> forecast_time_units : hours
>
> initial_time : 09/26/2010 (18:00)
>
> remap : remapped via ESMF_regrid_with_weights: Bilinear
>
> missing_value : 1e+20
>
>
>
> ---
>
> Variable: p
>
> Type: integer
>
> Total Size: 116 bytes
>
> 29 values
>
> Number of Dimensions: 1
>
> Dimensions and sizes: [lv_ISBL3 | 29]
>
> Coordinates:
>
> lv_ISBL3: [100..1000]
>
> Number Of Attributes: 2
>
> long_name : isobaric level
>
> units : Pa
>
>
>
> ---
>
> Variable: thetaN
>
> Type: float
>
> Total Size: 32485452 bytes
>
> 8121363 values
>
> Number of Dimensions: 3
>
> Dimensions and sizes: [lv_ISBL3 | 29] x [lat | 337] x [lon | 831]
>
> Coordinates:
>
> lv_ISBL3: [100..1000]
>
> lat: [ 1.. 85]
>
> lon: [ 150..358.5]
>
> Number Of Attributes: 5
>
> _FillValue : 1e+20
>
> long_name : potential temperature
>
> units : K
>
> remap : remapped via ESMF_regrid_with_weights: Bilinear
>
> missing_value : 1e+20
>
>
>
> --- (FROM tkReGr&lv_ISBL3)
>
> Variable: p
>
> Type: integer
>
> Total Size: 116 bytes
>
> 29 values
>
> Number of Dimensions: 1
>
> Dimensions and sizes: [lv_ISBL3 | 29]
>
> Coordinates:
>
> Number Of Attributes: 2
>
> long_name : isobaric level
>
> units : Pa
>
>
>
> ---
>
> Variable: ipv
>
> Type: float
>
> Total Size: 4480752 bytes
>
> 1120188 values
>
> Number of Dimensions: 3
>
> Dimensions and sizes: [thlev | 4] x [lat | 337] x [lon | 831]
>
> Coordinates:
>
> thlev: [325..370]
>
> lat: [ 1.. 85]
>
> lon: [ 150..358.5]
>
> Number Of Attributes: 4
>
> _FillValue : 1e+20
>
> long_name : Isentropic Potential Vorticity at 325K
>
> short_name : IPV
>
> units : K m2/kg/s
>
>
>
>
>
> Thanks!!
>
> Best,
>
> Kacie
>
> ---
>
> Kacie N. Shourd
>
> 드림
>
>
>
> Graduate Research Assistant
>
> Desert Research Institute
>
> Kacie.Shourd at dri.edu
>
> Work: (775) 674-7049
>
>
>
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