These climatologies show the Fractional occurrence or probability of encountering waves with peak vertical displacements greater than 1000 meters. They are based on runs of our mountain wave forecast model using daily global wind and temperature analyes from the National Center for Environmental Prediction (NCEP). The climatologies are compiled by running our mountain wave model for each day of the period in question, marking instances of inferred amplitudes over 1000 meters with a one, and summing over the entire period and dividing by the number of days. Thus, if a given ridge has waves of inferred amplitude larger than 1000 m at some altitude on 10 days of 31 day month it will be assigned a fractional occurrence of about 0.33 and its ridge symbol (an outline of its approximate size, orientation etc., see Ridge Database) in the following maps will be color-coded accordingly. Fractional occurrence of waves > 1000 m at 70 mbars (approximately 20 km altitude) is shown in the following plots.