[ncl-talk] EP-flux

[Dennis Shea]

What to say?

NCL's epflux function matches that at :
    http://www.esrl.noaa.gov/psd/data/epflux/

That attached plot for 7 Dec 2016 also includes contours of EP-divergence
(dashed are negative).

---

The epflux_1.ncl code contains ....

show_accel = 1    ; <=== plot acceleration (not EP divergence)

[SNIP]
  if (show_accel .eq. 1) then
      dudt at _FillValue = -999.0
      dudt(0,:) = dudt at _FillValue                  ; Hide the 1000 mb level
      res_con at cnLevelSpacingF        = 5.          ; Contour level Spacing
      plotvec2 = gsn_contour(wks,dudt,res_con)     ; Creates plot for
du/dt = div(F)/(a*cos(phi))
      overlay(plotvec,plotvec2)
  else
      EPdiv at _FillValue = -999.0
      EPdiv(0,:) = EPdiv at _FillValue                ; Hide the 1000 mb level
      res_con at cnLevelSpacingF        = 200.        ; Contour level Spacing
      plotvec3 = gsn_contour(wks,EPdiv,res_con)    ; Creates plot for div(F)
       overlay(plotvec,plotvec3)
  end if

is plotting 'acceleration' (dudt) not EP-divergence.

====

Attached is the script used. Also, for your perusal,
is the epflux function currently scheduled to be part
of the 6.4.0. Please offer suggestions for code improvements
or corrections.

The data used may readily be downloaded from

http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis.pressure.html

air.2016.nc, uwnd.2016.nc, vwnd.2016.nc

Regards

D


On Fri, Dec 9, 2016 at 9:37 AM, <hshp at mail.iap.ac.cn> wrote:

> Dear NCL group,
>
>      Based on many previous studies, the basic divergence of EP-flux
> (especially in the troposphere at mid-latitudes) should be negative.
> However, the results calculated by your program [https://www.ncl.ucar.edu/
> Applications/EPflux.shtml] are inconsistent the previous ones.
>
>     Also, the divergence displayed at the website [
> http://www.esrl.noaa.gov/psd/data/epflux/] is mainly positive in the
> troposphere.
>
>     Have you ever checked or thought about this issue?
> Looking forward to hearing from you.
> Best regards.
>
>
> Dr. Shengping He, Research Assistant
> Climate Change Research Center, Chinese Academy of Sciences
> Tel: +861082995191
> E-mail：hshp at mail.iap.ac.cn
>
>
>
>
>
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