U.S. Forts Daily Data and the Frequency of Extreme Events in the 19th Century

NOAA's Climate Database Modernization Program (CDMP) has keypunched substantial numbers of daily and at-hour climate observations for the period from the 1810s to the 1890s. Sufficient numbers of these records now exist for the second half of the 19th Century in the conterminous United States to characterize in a preliminary manner the secular variations in climate extremes measurable with daily data, such as heat waves, cold waves, and heavy precipitation events. Manual examinations of manuscript forms were utilized to supplement automated quality control procedures due to the nature of the observational records. Preliminary time series of indices representing the frequency of conterminous U.S. heat waves, cold waves, and heavy precipitation events display interesting behaviors in the 19th Century. There appears to be a relatively high frequency of heat waves in the mid-19th Century, and a relatively low frequency of heavy precipitation events in the 1880s and early 1890s, comparing both to the start of the modern cooperative observer record in the mid-1890s. Keypunching is continuing in the CDMP project, and newly updated results will be discussed.