OI SST Frequently Asked Questions

 

Table of Contents

  How do I change my old codes to read OIv2 data?
Where can I find climatology fields?
Why doesn't the sample code to read the data work on my system?
When are the near real time fields generated?
Where can I get the data in ascii?
Where can I get the data in NetCDF?
 

How do I change my old codes to read OIv2 data?

A sample code to read the OIv2 data is available in the README file in the ftp data directory.

For users that already have their own codes written to read the original OI data, the most obvious changes:
   - the data fields are 4-byte real rather than 2-byte integer.
   - you no longer need to divide by 100.
   - the fields are in individual  and yearly files

The key change that could slip by unnoticed is that the grid is shifted 180 degrees:
   OI.v1 started at 179.5W
   OI.v2 starts at 0.5E

A few points on the land mask changed.
The mask file is now direct access, ieee binary, rather than ascii.
The new sample source code reads the new mask.

Data set additions:
  - The relative error variance is included in a separate field with the weekly data.
  - The estimated ice concentration is included in a separate field in both
     weekly and monthly data.

If you convert the total fields to anomalies using our climatology, we
strongly suggest you switch to the new climatology (see below) derived from OIv2.
If you use the old climatology with the OI.v2 you will see large anomalies near the ice
edge, particularly in summer months.

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Where can I find climatology fields?

A climatology derived from these fields with a base period of 1971-2000 is described at:
     http://www.cpc.noaa.gov/products/predictions/30day/SSTs/sst_clim.html
and available at:
      ftp://ftp.cpc.ncep.noaa.gov/wd52yx/sstclim
This is a product of the Climate Prediction Center.  Contact Yan Xue (Yan.Xue@noaa.gov) for further information.

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Why doesn't the sample code to read the data work on my system?

You may have to swap the bytes in order to read the data on a  pc or other "little-endian" system.
There may be an option to do that easily with your fortan compiler.
Also, there is a fortran control word at the beginning and end of each record.
This indicates the number of actual bytes of data in that record.
If your pc's compiler does not expect these, you may have to skip them.
The data file structure (for weekly data) is as follows:

   (for each time step)
Header record:  1 4-byte fortran control word
                8 4-byte integer words (Dates and index)
                1 4-byte fortran control word
SST record:     1 4-byte fortran control word
                360*180 4-byte real words (SST values)
                1 4-byte fortran control word
Error record:   1 4-byte fortran control word
                360*180 4-byte real words (relative error variance)
                1 4-byte fortran control word
Ice record:     1 4-byte fortran control word
                360*180 1-byte character words (Ice)
                1 4-byte fortran control word

The code can be modified to skip a dummy four byte integer word at the beginning and end of each read statement.
The monthly data is similar, but does not include the Error record.

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When are near real time fields generated?

The real-time weekly fields run Sunday through Saturday and are generated early Monday morning.
We have to wait until we can interpolate weekly fields to the last day of the month to generate a complete
monthly field.  Thus, the full monthly fields are updated according to the following schedule:

           Last Day of           Analysis
           Month Falls on      Completed on
           --------------------------------
           Sunday                 8th
           Monday                 7th
           Tuesday                6th
           Wednesday              5th
           Thursday              11th
           Friday                10th
           Saturday               9th

It is best to wait until late morning (US Eastern Time) to pick up new fields to give us time to ensure the analysis ran properly.

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Where can I get the data in ascii?

The Data Support Section (DSS) of NCAR makes both weekly and monthly OIv2 data available in ASCII at:
      http://rda.ucar.edu/datasets/ds277.0/

If the DSS archive is not up-to-date, look for the most recent data at:
      ftp://ftp.emc.ncep.noaa.gov/cmb/sst/oisst_v2/ASCII_UPDATE  for weekly data
and:
      ftp://ftp.emc.ncep.noaa.gov/cmb/sst/oimonth_v2/ASCII_UPDATE  for monthly data

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Where can I get the data in NetCDF?

The NOAA Earth System Research Laboratory (ESRL) makes these data availabe in NetCDF at: http://www.cdc.noaa.gov/cdc/data.noaa.oisst.v2.html

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Page last updated: 31 May 2012