Does anyone have any suggestions on either a function
for divergence to apply directly to lat2d x lon2d data
or how to refine my approach below (1st fit to a regular
grid and then compute divergence)?
Dear Michael
I would compute the divergence on the 2d model grid (using the model's own
discretization) from the vertically interpolated winds, then average in time
and at the very end interpolate to the new 2d grid.
Regards,
Andrea
--
Andrea N. Hahmann
Senior Scientist
Wind Energy Division
Risų DTU
Technical University of Denmark
Risų National Laboratory for Sustainable Energy
Frederikborgvej 399, P.O. Box 49
4000 Roskilde, Denmark
Direct +45 4677 5471
Mobil: +45 2133 0550
ahah@risoe.dtu.dk
www.risoe.dtu.dk
> From: Michael Notaro <mnotaro@wisc.edu>
> Date: Fri, 25 Mar 2011 09:40:36 -0500
> To: ncl-talk NCL <ncl-talk@ucar.edu>
> Subject: divergence calculations
>
> My calculated monthly mean 250-hPa divergence map
> looks extremely noisy (see attached plots of divergence
> and interpolated u wind).
>
> I started with 6-hourly U and V on a regional model lat2d x lon2d
> grid. I used int2p to interpolate U and V from sigma to 250 hPa.
> Then I used rcm2rgrid to interpolate to a fixed grid. Then I used
> uv2dv_cfd to compute 250 hPa divergence of these interpolated
> wind components. Finally I averaged the divergences across
> all time steps to get the monthly mean.
>
> Any suggestions? I assume the interpolated wind components
> are not the best, and so the derivates for divergence look messy.
>
> Michael
>
>
>
>
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/shea_util.ncl"
> begin
>
> nlat=148
> nlon=158
>
> ctl=new((/8,148,158,10/),float)
>
> months=(/"MAR","APR","MAY","JUN","JUL","AUG","SEP","OCT"/)
>
> yrs=(/"1991","1992","1993","1994","1995","1996","1997","1998","1999","2000"/)
> yr=(/"91","92","93","94","95","96","97","98","99","00"/)
> mns=(/"03","04","05","06","07","08","09","10"/)
> hr=(/"06","00","00","00","00","00","00","00"/)
> days=(/31,30,31,30,31,31,30,31/)
>
> do iy=0,9
> do im=0,7
> print(iy+" "+im)
> if ( (yrs(iy)+""+mns(im).eq."199103").or.(yrs(iy)+""+mns(im).eq."199406")
> ) then
> a=addfile("../con9096/Southwest_ATM."+yrs(iy)+""+mns(im)+"0106.nc","r")
> else
> a=addfile("../con9096/Southwest_ATM."+yrs(iy)+""+mns(im)+"0100.nc","r")
> end if
> if ( (yrs(iy)+""+mns(im).eq."199103").or.(yrs(iy)+""+mns(im).eq."199406")
> ) then
> u=a->u(3::,:,:,:)
> v=a->v(3::,:,:,:)
> ps=a->ps(3::,:,:)
> time=a->time(3::)
> else
> if (mns(im).eq."03") then
> u=a->u(4::,:,:,:)
> v=a->v(4::,:,:,:)
> ps=a->ps(4::,:,:)
> time=a->time(4::)
> else
> u=a->u(:,:,:,:)
> v=a->v(:,:,:,:)
> ps=a->ps(:,:,:)
> time=a->time
> end if
> end if
> lat2d=a->xlat
> lon2d=a->xlon
> sigma=a->sigma
> ptop=a->ptop ; hPa
> nt=dimsizes(time)
>
> lat=fspan(min(lat2d),max(lat2d),148)
> lon=fspan(min(lon2d),max(lon2d),158)
> lat!0="lat"
> lat&lat=lat
> lat@units="degrees_north"
> lon!0="lon"
> lon&lon=lon
> lon@units="degrees_east"
>
> p=new((/nt,18,148,158/),float)
> do ilev=0,17
> p(:,ilev,:,:)=ps*sigma(ilev)
> end do
> copy_VarCoords(u,p)
>
> ulev=int2p(p(time|:,iy|:,jx|:,kz|:),u(time|:,iy|:,jx|:,kz|:),250.,1)
> vlev=int2p(p(time|:,iy|:,jx|:,kz|:),v(time|:,iy|:,jx|:,kz|:),250.,1)
>
> ulevel=ulev(:,:,:,0)
> vlevel=vlev(:,:,:,0)
> copy_VarCoords(ps,ulevel)
> copy_VarCoords(ps,vlevel)
>
> ugrid=rcm2rgrid(lat2d,lon2d,ulevel,lat,lon,0)
> vgrid=rcm2rgrid(lat2d,lon2d,vlevel,lat,lon,0)
> ugrid!0="time"
> ugrid!1="lat"
> ugrid!2="lon"
> ugrid&time=time
> ugrid&lat=lat
> ugrid&lon=lon
> copy_VarCoords(ugrid,vgrid)
>
> div=uv2dv_cfd (ugrid,vgrid,lat,lon,2)
> copy_VarCoords(ps,div)
>
> ctl(im,:,:,iy)=dim_avg_Wrap(div(iy|:,jx|:,time|:))
>
> out=addfile("out.nc","c")
> out->ctl=ctl(im,:,:,iy)
> out->ugrid=ugrid
> out->vgrid=vgrid
>
>
> delete(a)
> delete(time)
> delete(u)
> delete(v)
> delete(ps)
> delete(p)
> delete(ulev)
> delete(vlev)
> delete(ugrid)
> delete(vgrid)
> delete(div)
>
> end do
> end do
>
> end
>
>
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Received on Sat Mar 26 12:44:02 2011
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