A procedure for removing the synoptic climate signal from environmental data

Using weather‐type frequencies from a synoptic climatology, a technique is presented that discriminates between within‐type and between‐type variations in a time series of climate‐related environmental data. The removal of the synoptic climate signal, or declimatizing, is based on normalizing the data by the mean annual weather‐type frequencies for the study period. Declimatizing is illustrated symbolically and with a worked hypothetical example. An application of the procedure to visibility data from Pittsburgh, Pennsylvania demonstrates its utility in decomposing complex climate‐related environmental data into its component synoptic and non‐synoptic influences. The methodology can also distinguish the relative importance of between‐type and within‐type changes in a synoptic climatology.