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Re: [ferret_users] shifted Hovmoller plot



Hi Fan,
Thank you for the report. I can replicate the behavior with Ferret statements.
yes? define axis/t="1-jan-2006:12":"5-jan-2006:12":86400/units=seconds/t0=1-jan-1970/calendar=julian  time5
yes? define axis/x=100w:100e:5/units=degrees_east xax
yes? let tvar = L[gt=time5]
yes? let xtvar = tvar + sin(x[gx=xax]/40)
yes? shade xtvar
The time axis I define here is a bit different from the one in your file. The one in my example has the time coordinates in the middle of the timestep and yours is at one edge. Both are legal definitions and both show this same behavior. The fact that we have a Julian calendar does not affect things. We'll look into this.

Ansley

On 2/19/2014 9:44 AM, Fan Fang wrote:
I am trying to use Ferret to do a Hovmoller plot with a simple netCDF file.

Wonder why the Hovmoller plot came out slightly shifted upward (by ~6 hours; attached).  The header of the CDL is below.  I can send the netcdf file also if needed but thought the problem could be just some mistake using Ferret.

Thanks.

-Fan

> ferret/bin/ferret
     NOAA/PMEL TMAP
     FERRET v6.85 
     Linux 2.6.32-358.23.2.el6.x86_64 64-bit - 11/12/13
     19-Feb-14 12:28    

yes? use test.nc
yes? show data
     currently SET data sets:
    1> ./test.nc  (default)
 name     title                             I         J         K         L         M         N
 OMAERUVD_003_FINALAEROSOLEXTOPTICALDEPTH388
          Aerosol Optical Depth 388 nm (n  1:360     ...       ...       1:5       ...       ...
 
yes? shade OMAERUVD_003_FINALAEROSOLEXTOPTICALDEPTH388


The values of the time and 'time_bnds' variables are:

time = 1136073600, 1136160000, 1136246400, 1136332800, 1136419200 ;
time_bnds =
  1136073600, 1136160000,
  1136160000, 1136246400,
  1136246400, 1136332800,
  1136332800, 1136419200,
  1136419200, 1136505600 ;

netcdf test {
dimensions:
    bnds = 2 ;
    time = UNLIMITED ; // (5 currently)
    lon = 360 ;
variables:
    int time_bnds(time, bnds) ;
    float OMAERUVd_003_FinalAerosolExtOpticalDepth388(time, lon) ;
        OMAERUVd_003_FinalAerosolExtOpticalDepth388:_FillValue = -1.267651e+30f ;
        OMAERUVd_003_FinalAerosolExtOpticalDepth388:units = "1" ;
        OMAERUVd_003_FinalAerosolExtOpticalDepth388:title = "Final Aerosol Extinction Optical Depth at 388 nm" ;
        OMAERUVd_003_FinalAerosolExtOpticalDepth388:UniqueFieldDefinition = "OMI-Specific" ;
        OMAERUVd_003_FinalAerosolExtOpticalDepth388:missing_value = -1.267651e+30f ;
        OMAERUVd_003_FinalAerosolExtOpticalDepth388:origname = "FinalAerosolExtOpticalDepth388" ;
        OMAERUVd_003_FinalAerosolExtOpticalDepth388:fullnamepath = "/HDFEOS/GRIDS/Aerosol NearUV Grid/Data Fields/FinalAerosolExtOpticalDepth388" ;
        OMAERUVd_003_FinalAerosolExtOpticalDepth388:orig_dimname_list = "XDim " ;
        OMAERUVd_003_FinalAerosolExtOpticalDepth388:standard_name = "finalaerosolextopticaldepth388" ;
        OMAERUVd_003_FinalAerosolExtOpticalDepth388:quantity_type = "Total Aerosol Optical Depth" ;
        OMAERUVd_003_FinalAerosolExtOpticalDepth388:product_short_name = "OMAERUVd" ;
        OMAERUVd_003_FinalAerosolExtOpticalDepth388:product_version = "003" ;
        OMAERUVd_003_FinalAerosolExtOpticalDepth388:long_name = "Aerosol Optical Depth 388 nm (near-UV), OMI, 1 x 1 deg." ;
    float lon(lon) ;
        lon:standard_name = "longitude" ;
        lon:units = "degrees_east" ;
        lon:long_name = "Longitude" ;
    int time(time) ;
        time:standard_name = "time" ;
        time:units = "seconds since 1970-01-01 00:00:00" ;
        time:bounds = "time_bnds" ;
        time:calendar = "JULIAN" ;

// global attributes:
        :Conventions = "CF-1.4" ;
        :start_time = "2006-01-01T00:00:00Z" ;
        :end_time = "2006-01-05T23:59:59Z" ;
        :temporal_resolution = "daily" ;
        :nco_openmp_thread_number = 1 ;
        :NCO = "4.3.1" ;
        :plot_hint_title = "Latitude-Averaged Hovmoller ( 90S - 90N )" ;
        :plot_hint_subtitle = "daily 1 x 1 deg. Aerosol Optical Depth 388 nm (near-UV), OMI, 1 x 1 deg. [OMAERUVd v3]" ;
        :plot_hint_x_axis_label = "Longitude" ;
        :plot_hint_y_axis_label = "Time" ;
        :plot_hint_caption = "Selected latitude range was 90S - 90N. The variable Aerosol Optical Depth 388 nm (near-UV), OMI, 1 x 1 deg. [OMAERUVd v3] has a limited data extent of 90S - 90N.  The longitude range in the title reflects the data extent of the subsetted granules that went into making this result." ;
}


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