1960   Entire grid contents are set to missing data 
1961   Entire grid contents are set to missing data 
1962   Entire grid contents are set to missing data 
1963   Entire grid contents are set to missing data 
1964   Entire grid contents are set to missing data 
1965   Entire grid contents are set to missing data 
1966   Entire grid contents are set to missing data 
1967   Entire grid contents are set to missing data 
1968   Entire grid contents are set to missing data 
1969   Entire grid contents are set to missing data 
1970   Entire grid contents are set to missing data 
1971   Entire grid contents are set to missing data 
1972   Entire grid contents are set to missing data 
1973   Entire grid contents are set to missing data 
1974   Entire grid contents are set to missing data 
1975   Entire grid contents are set to missing data 
1976   Entire grid contents are set to missing data 
1977   Entire grid contents are set to missing data 
1978   Entire grid contents are set to missing data 
1979   Entire grid contents are set to missing data 
1980   Entire grid contents are set to missing data 
1981   Entire grid contents are set to missing data 
1982   Entire grid contents are set to missing data 
1983   Entire grid contents are set to missing data 
1984   Entire grid contents are set to missing data 
1985   Entire grid contents are set to missing data 
1986   Entire grid contents are set to missing data 
1987   Entire grid contents are set to missing data 
1988   Entire grid contents are set to missing data 
1989   Entire grid contents are set to missing data 
1990   Entire grid contents are set to missing data 
1991   Entire grid contents are set to missing data 
1992   Entire grid contents are set to missing data 
1993   Entire grid contents are set to missing data 
1994   Entire grid contents are set to missing data 
1995   Entire grid contents are set to missing data 
1996   Entire grid contents are set to missing data 
1997   Entire grid contents are set to missing data 
1998   Entire grid contents are set to missing data 
1999   Entire grid contents are set to missing data 
2000   Entire grid contents are set to missing data 
2001   Entire grid contents are set to missing data 
2002   Entire grid contents are set to missing data 
2003   Entire grid contents are set to missing data 
2004   Entire grid contents are set to missing data