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Description of Changes in Climatic Indices in USA over 25 Years (1989 – 2013)
Citation:
Nash, M. AND J. Christensen. Description of Changes in Climatic Indices in USA over 25 Years (1989 – 2013). U.S. Environmental Protection Agency, Washington, DC, EPA/600/S-17/434, 2018.
Impact/Purpose:
It is our desire to make the methodology, data and analyses available for research efforts such as these and better understand the trends of precipitation, temperature, and their interactions in hydrological, societal, biological and ecological systems.
Description:
The spatial distribution of long-term changes in climatic factors and its relation with vegetation cover, human health, hydrology and many other ecosystem processes help to identify the consequences of climatic factors changes. In recent studies, the significant changes of selected climatic factors over 25 years has been associated with changes in greenness (Nash et al. 2016), with shifts in health outcomes (Perry et al. 2011), and with fog formation (Hiatt et al., 2012) as examples of the impacts of climate factors on ecosystems and societal benefits. This report concentrates on the methodology and potential future uses for long-term climate factor trends, and trends of derived climatic factors and indices. Analyses of all factors over the 25 years (1989-2013) show the magnitude and direction of significant changes on different time scales (monthly, annual average, and seasonal). Additionally, annual averages, coefficient of variation (CV), first and 99th percentile were also presented to show the differences in patterns of variability and extreme values. The climate factors considered are: Minimum, maximum and dew temperatures, and precipitation. Derived climatic factors considered are: potential evapotranspiration (PET); and two climatic indices are a moisture index and apparent temperatures (AT) index, which is also known as the Heat Index (Smoyer-Timon and Rainham 2001).