A Revised U.S. Climate Extremes Index

Abstract

A revised framework is presented that quantifies observed changes in the climate of the contiguous United States through analysis of a revised version of the U.S. Climate Extremes Index (CEI). The CEI is based on a set of climate extremes indicators that measure the fraction of the area of the United States experiencing extremes in monthly mean surface temperature, daily precipitation, and drought (or moisture surplus). In the revised CEI, auxiliary station data, including recently digitized pre-1948 data, are incorporated to extend it further back in time and to improve spatial coverage. The revised CEI is updated for the period from 1910 to the present in near-real time and is calculated for eight separate seasons, or periods.Results for the annual revised CEI are similar to those from the original CEI. Observations over the past decade continue to support the finding that the area experiencing much above-normal maximum and minimum temperatures in recent years has been on the rise, with infrequent occurrence of much belownormal mean maximum and minimum temperatures. Conversely, extremes in much below-normal mean maximum and minimum temperatures indicate a decline from about 1910 to 1930. An increasing trend in the area experiencing much above-normal proportion of heavy daily precipitation is observed from about 1950 to the present. A period with a much greater-than-normal number of days without precipitation is also noted from about 1910 to the mid-1930s. Warm extremes in mean maximum and minimum temperature observed during the summer and warm seasons show a more pronounced increasing trend since the mid-1970s. Results from the winter season show large variability in extremes and little evidence of a trend. The cold season CEI indicates an increase in extremes since the early 1970s yet has large multidecadal variability.

Evidence linking Arctic amplification to extreme weather in mid‐latitudes

“…Corresponding trends in wave amplitude (third row) are also positive at most longitudes, with the largest increases in the central U.S. and central N. Atlantic. These tendencies favor warmer, more persistent conditions along the N. American east coast and in the N. Atlantic, and may have contributed to the dramatic increase in maximum temperature extremes in those areas during fall, as shown in the Climate Extreme Index (available from NOAA's National Climate Data Center, http://www.ncdc.noaa.gov/extremes/ cei/ [Gleason et al, 2008]). …”

Climate change impacts on extreme events in the United States: an uncertainty analysis

“…In addition, there have been increases in the number of heavy precipitation events over the last half of the 20th century in more regions than there have been decreases (IPCC 2013). The overall most consistent trends toward increases in heavier precipitation events are found in North America (Peterson et al 2008;DeGaetano 2009;Pryor et al 2009;Gleason et al 2008). Models project substantial increases in temperature extremes by the end of the 21st century with the length, frequency, and/or intensity of warm spells and heat waves increasing over most land areas (Kharin et al 2007;Sterl et al 2008;Orlowsky and Seneviratne 2012).…”

North American extreme temperature events and related large scale meteorological patterns: a review of statistical methods, dynamics, modeling, and trends

“…Traditional methods in climate research for detecting trends in temperature extremes tend to focus on the relative frequency of exceeding a high threshold or of falling below a low threshold, as well as indices derived from such rates (Karl et al 1996;Gleason et al 2008). Such approaches generally fail to give a complete picture of trends in temperature extremes as they neglect the intensity of the event.…”