graupel vs snowpack

graupel

noun
  • A precipitation that forms when supercooled droplets of water condense on a snowflake. 

  • The result of this process, a small ball of rime. 

snowpack

noun
  • An accumulation of packed snow, usually the seasonal amount. 

How often have the words graupel and snowpack occurred in a corpus of books? (source: Google Ngram Viewer )