Files are simple binary with no header.  The domain size is 103 x 121.  The resolution is 24-km.  

A sample fortran routine to read the data is available in the ZIP with the data.
The file is called readbin.f.
This can be used as-is or modified to c or another language. 
The same fortran routine is also provided below:
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C     read.f
C     pgf77 -byteswapio read.f -o read
 
      parameter(ix=103,iy=121)
      dimension a(ix,iy)
      open(1,file='199012RAIN.2',status='old',form='unformatted')
      read(1)((a(i,j) ,i=1,ix),j=1,iy)
      close(1)
      Stop
      end

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Please direct any questions to David Bromwich (bromwich.1@osu.edu)