netCDF to GEMPAK is not a straightforward conversion: from https://www.unidata.ucar.edu/support/help/MailArchives/gempak/msg03507.html "The dcreanal program was written to convert reanalysis data files which used the COARDS convention for storage in NetCDF. If the files you have are not using the COARDS convention, then the converter would have to be modified to the CDL of the data you have. It is difficult to create a general NetCDF converter since the storage convention is user defined. The best direction is to create converters for common storage conventions like CF or COARDs." additional info at https://www.unidata.ucar.edu/support/help/MailArchives/netcdf/msg02684.html I attached the source code from the second link but I can't speak for it myself. Michael James Unidata Program Center Boulder, CO On Thu, Jan 18, 2018 at 9:23 AM, ashwin .D <address@hidden> wrote: > New Client Reply: Question regarding relative vorticity calculation in > GEMPAK > > Hello, > Thanks for your response. I have data in a netCDF form. Will > that work ? > > Regards, > Ashwin. > > address@hidden> wrote: > > > > > > I am just starting to learn about GEMPAK's enormous capabilities and I > > > had a question regarding the calculation of relative vorticity. In the > > > documentation here - > > > > > > https://www.unidata.ucar.edu/software/gempak/man/parm/apxB.html > > > > > > you have vorticity defined as - > > > > > > VOR ( V ) = DDX ( v ) - DDY ( u ) > > > > > > but in the code comments you have it defined as - > > > > > > * * > > > * VOR ( V ) = DDX(v) - DDY(u) - v*{(mx/my)*[d(my)/dx]} + * > > > * + u*{(my/mx)*[d(mx)/dy]} > > > > It appears that you are comparing the calculation for vorticity from > > apxB.html to a code comment rather than the actual code that calculated > > vorticity. The commented formula includes second-order components which > > are not included in the calculation (guessing here, since I've not dug > > through code to find where this is from - that's where a reference would > > help, source code file name and line number). > > > > I do not have a test script to calculate PV from reanalysis data, I do > now > > know what exactly your reanalysis data are - already in GEMPAK grid form > or > > is it in grib2 (or something else?) If the data exists as a GEMPAK file > > then you are good to go and can just use the PVOR grid parameter > > > > from https://www.unidata.ucar.edu/software/gempak/man/parm/apxB.html > > > > PVOR Potential vorticity in a layer > > PVOR ( S, V ) = - GRAVTY * AVOR ( VLAV (V) ) * LDF ( THTA ) / > > ( 100 * LDF ( PRES ) ) > > The 100 converts millibars to Pascals. > > Units are Kelvins / meters / Pascals / seconds**3 > > (note that GRAVTY is included). PVOR works on a layer > > in PRES or THTA coordinates. In isobaric coordinates, > > the scalar operand, S, is THTA, THTE, or THES. In > > isentropic coordinates, the scalar operand, S, is > > PRES. Multiplying by 10**6 gives standard PV units. > > > > Ticket Details > > =================== > > Ticket ID: ROY-668075 > > Department: Support GEMPAK > > Priority: Normal > > Status: Open > > =================== > > NOTE: All email exchanges with Unidata User Support are recorded in the > > Unidata inquiry tracking system and then made publicly available through > > the web. If you do not want to have your interactions made available in > > this way, you must let us know in each email you send to us. > > > > > > > > > > Ticket Details > =================== > Ticket ID: ROY-668075 > Department: Support GEMPAK > Priority: Normal > Status: Open > Link: https://andy.unidata.ucar.edu/esupport/staff/index.php?_m= > tickets&_a=viewticket&ticketid=28997 > > Ticket Details =================== Ticket ID: ROY-668075 Department: Support GEMPAK Priority: Normal Status: Open =================== NOTE: All email exchanges with Unidata User Support are recorded in the Unidata inquiry tracking system and then made publicly available through the web. If you do not want to have your interactions made available in this way, you must let us know in each email you send to us.
Attachment:
dcreanal.tar
Description: Unix tar archive