TY - JOUR
T1 - A comparison of daily temperature-averaging methods
T2 - Spatial variability and recent change for the CONUS
AU - Bernhardt, Jase
AU - Carleton, Andrew M.
AU - LaMagna, Chris
N1 - Funding Information:
Acknowledgments. This paper represents a portion of the first author’s Ph.D. dissertation at Penn State University. We are grateful for the guidance and insight provided by dissertation committee members Drs. Brent Yarnal, Jon Nese, and Martin Tingley. Partial funding for this research was provided by the Pennsylvania Space Grant Consortium as part of its Graduate Research Fellowship Program at Penn State.
Publisher Copyright:
© 2018 American Meteorological Society.
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2018/2/1
Y1 - 2018/2/1
N2 - Traditionally, the daily average air temperature at a weather station is computed by taking the mean of two values, the maximum temperature (Tmax) and the minimum temperature (Tmin), over a 24-h period. These values form the basis for numerous studies of long-term climatologies (e.g., 30-yr normals) and recent temperature trends and changes. However, many first-order weather stations-such as those at airports-also record hourly temperature data. Using an average of the 24 hourly temperature readings to compute daily average temperature has been shown to provide a more precise and representative estimate of a given day's temperature. This study assesses the spatial variability of the differences in these two methods of daily temperature averaging [i.e., (Tmax + Tmin)/2; average of 24 hourly temperature values] for 215 first-order weather stations across the conterminous United States (CONUS) over the 30-yr period 1981-2010. A statistically significant difference is shown between the two methods, as well as consistent overestimation of temperature by the traditional method [(Tmax + Tmin)/2], particularly in southern and coastal portions of the CONUS. The explanation for the long-term difference between the two methods is the underlying assumption for the twice-daily method that the diurnal curve of temperature is symmetrical. Moreover, this paper demonstrates a spatially coherent pattern in the difference compared to the most recent part of the temperature record (2001-15). The spatial and temporal differences shown have implications for assessments of the physical factors influencing the diurnal temperature curve, as well as the exact magnitude of contemporary climate change.
AB - Traditionally, the daily average air temperature at a weather station is computed by taking the mean of two values, the maximum temperature (Tmax) and the minimum temperature (Tmin), over a 24-h period. These values form the basis for numerous studies of long-term climatologies (e.g., 30-yr normals) and recent temperature trends and changes. However, many first-order weather stations-such as those at airports-also record hourly temperature data. Using an average of the 24 hourly temperature readings to compute daily average temperature has been shown to provide a more precise and representative estimate of a given day's temperature. This study assesses the spatial variability of the differences in these two methods of daily temperature averaging [i.e., (Tmax + Tmin)/2; average of 24 hourly temperature values] for 215 first-order weather stations across the conterminous United States (CONUS) over the 30-yr period 1981-2010. A statistically significant difference is shown between the two methods, as well as consistent overestimation of temperature by the traditional method [(Tmax + Tmin)/2], particularly in southern and coastal portions of the CONUS. The explanation for the long-term difference between the two methods is the underlying assumption for the twice-daily method that the diurnal curve of temperature is symmetrical. Moreover, this paper demonstrates a spatially coherent pattern in the difference compared to the most recent part of the temperature record (2001-15). The spatial and temporal differences shown have implications for assessments of the physical factors influencing the diurnal temperature curve, as well as the exact magnitude of contemporary climate change.
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U2 - 10.1175/JCLI-D-17-0089.1
DO - 10.1175/JCLI-D-17-0089.1
M3 - Article
AN - SCOPUS:85040908290
SN - 0894-8755
VL - 31
SP - 979
EP - 996
JO - Journal of Climate
JF - Journal of Climate
IS - 3
ER -