1this summary of surface airways hrly data prints the number of months in each
 year for which hours/day .ge.2. and days/month .ge.10 for the given parameter
 and period, i.e. blank = none, 1-9=1-9, a = 10, b = 11, * = 12

 global radiation         (GRAD)      4    4    5    5    6    6    7    7    8    8    9    9
                (1936-1995) >>>   ----0----5----0----5----0----5----0----5----0----5----0----5
 no data for this parameter