However, Novlan and Gray (1974) utilized rawinsonde and pibal datasets from 1948 to 1972 for the United States and 1950-71 for Japan, the largest scope at that time.
Observation data includes NCEP Global surface and upper air observational weather data, including airport ground stations, radiosondes, pibals and both aircraft reports and satellite data with measurements of pressure, geopotential height, air temperature, dew point temperature, wind direction and wind speed.