Sep 23, 2011

Evolution and Distribution of Record-Breaking High and Low Monthly Mean Temperatures

by
Amalia Anderson and Alexander Kotinski
,
American Meteorological Society
  • Examines the ratio of record highs to record lows for monthly mean temperatures within the continental United States for 1900–2006
  • Examines the spatial and seasonal aspects of theses trends
  • Uses the U.S. Historical Climatology Network (USHCN) monthly temperatures dataset
  • States that monthly means are less noisy than daily values, and are therefore more sensitive to changes in mean temperature and the evolving relationship between record highs and lows
  • Uses time series within the period 1900–2006 with durations of 90–106 years
  • Finds that time series length and time period can significantly affect the ratio of the ensemble sum of record highs to the ensemble sum of record lows occurring in a particular year
  • Considers and compares the ratio of record highs to lows throughout two time periods: 1950–2006 and 1900–2006
  • Finds that the ratio of record highs to record lows is about 13:1 in 2006, with 1950 as the first year and 25:1 with 1900 as the first year
  • Finds that global ratios increase throughout 1920–2006 whereas continental U.S. ratios decrease from about 1940 to 1970
  • Finds that the greatest excess of record highs occurs in February (≈2:1) and the greatest excess of record lows occurs in October (≈2:3)
  • Finds that ratios are pronounced in certain regions: in February in the Midwest the ratio ≈ 5:2, and in October in the Southeast the ratio ≈ 1:2