Daily Sea Suaface Temperature Data analysis by Japan Meteorological Agency (JMA)

This file contains analysis data of SST provided by the Japan Meteorological Agency. Each file consists of 121 lines of characters. The first line indicates the date of the analysis, as below.
1997    4  1          1997  4  1   1997  4  1

The second line is the data for the band between 49.75 to 50 degrees North. A 0.25 by 0.25 box data are presented with three digit integers in tenth of degrees Centigrade from 110 to 110.25 degrees East to 159.75 to 160 degrees East. The third line and onward are similar but the latitude goes southward to between 20N and 20.25N in the 121st line. The following is an example of FORTRAN statements to read the data. 999 and 888 mean land and sea ice, respectively. 777 means that the data is unknown for other reasons.

      dimension isst(200,120)
c       isst(1,1) = sst in 49.75N to 50N, 110E to 110.25E
c       iy, im, and id are year, month, and day
      read(10,510) iy,im,id
 510  format(i4,i5,i3)
      do 100 j=1,120 
      read(10,500) (isst(i,j),i=1,200)
 500  format(200I3)

Note on the SST analysis
JMA started, in March 1996, daily high resolution sea surface temperature (SST) analysis for the region between 20N and 50N and between 120E and 160E. The resolution is a quarter degree.
An optimal interpolation method is employed and the first guess field is given by linearly interpolating the climatological SST data of every one degree that JMA produced. The parameters used in the optimal interpolation are determined by examining the statistical characteristics of observations.
The analysis uses sea surface observation by NOAA and the in situ observation by ships and buoys. The data from the ships which make reports with bias or standard error larger than that of typical observation vessels are excluded from the process. The all the in-situ data within the spacial and temporal box of 1 day * 0.25 degree * 0.25 degree are averaged to give a representative value for that box, and these representative values are fed to the optimal interpolation as the 'observations'.
To get the interpolated value at each of the grind points, the 'observations' for the past 5 days within a half of the the typical spacial scale of the variation for the points are used. The typical spacial scale of the variation is estimated by examining the NOAA sst and varies from 40 km to 400km. In practice, in order to ensure that the interpolation is made with a sufficient number of input data, the minimum scale is set to be 200 km.


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