Science Source

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

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