Mean seasonal density charts for the Northern hemisphere for 5-km increments of altitude between 30 and 60 km are presented in this report, along with estimates of the day-to-day variations around the mean seasonal values. This meets the need for a climatology of atmospheric density at constant altitudes above radiosonde levels. These charts are based on compilations of data by workers at the National Meteorological Center, NOAA, who combined data from TIROS operational vertical sounders with meteorological rocketsonde observations to produce once-weekly analyses of height and temperature fields for the Northern hemisphere at the 5, 2, 1, and .4 mb levels for the period July 1976 through April 1980.