U.S. Daily Temperatures: The Meaning of Extremes in the Context of Nonnormality

Huybers, Peter; McKinnon, Karen A.; Rhines, A. N.; Tingley, Martin

doi:10.1175/jcli-d-14-00216.1

Cited by 53 publications

(55 citation statements)

References 45 publications

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“…Such connections are consistent with previous studies (14,16,17), particularly in the central part of the United States (20), and help us understand the model tendencies of producing greater numbers of daily record high maximum temperatures compared with observations (Fig. 2).…”

Section: Significancesupporting

confidence: 90%

US daily temperature records past, present, and future

Meehl

Tebaldi

Adams‐Smith

2016

Proc. Natl. Acad. Sci. U.S.A.

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Observed temperature extremes over the continental United States can be represented by the ratio of daily record high temperatures to daily record low minimum temperatures, and this ratio has increased to a value of about 2 to 1, averaged over the first decade of the 21st century, albeit with large interannual variability. Two different versions of a global coupled climate model (CCSM4), as well as 23 other coupled model intercomparison project phase 5 (CMIP5) models, show larger values of this ratio than observations, mainly as a result of greater numbers of record highs since the 1980s compared with observations. This is partly because of the "warm 1930s" in the observations, which made it more difficult to set record highs later in the century, and partly because of a trend toward less rainfall and reduced evapotranspiration in the model versions compared with observations. We compute future projections of this ratio on the basis of its estimated dependence on mean temperature increase, which we find robustly at play in both observations and simulations. The use of this relation also has the advantage of removing dependence of a projection on a specific scenario. An empirical projection of the ratio of record highs to record lows is obtained from the nonlinear relationship in observations from 1930 to 2015, thus correcting downward the likely biased future projections of the model. For example, for a 3°C warming in US temperatures, the ratio of record highs to lows is projected to be ∼15 ± 8 compared to the present average ratio of just over 2. A n analysis of observed continental US record high maximum and record low minimum daily temperatures in a quality-controlled dataset of daily station data from 1950 to 2006 showed that the value of the ratio of record highs to record lows has been increasing over the United States since the late 1970s (1). Although there is considerable interannual variability in the ratio, which is to be expected when it is based on temperature time series with large interannual variability (2), averages of this ratio over the first decade of the 21st century had a value of about 2-1. This was a reflection of the increase of mean temperature and a shift of its distribution, affecting the tail behavior, such that, on average, for every one daily record low minimum, there were roughly two record high maxima. This result was subsequently reproduced (3) and was also shown for Europe (4). A similar ratio of about 2-1 for monthly temperature records over Australia was shown for roughly this same period (5). As noted in other studies (6), there are geographic and seasonal characteristics to these records that depend on the variance of the temperature time series (7). Possible future increases to this ratio over the United States were shown for one future emission scenario (1).Several questions were raised in these studies that we address here. First, the previous analysis (1) started in 1950 because of the desire to use the more abundant and higher-quality postwar daily temperature data. Ho...

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Section: Significancesupporting

confidence: 90%

US daily temperature records past, present, and future

Meehl

Tebaldi

Adams‐Smith

2016

Proc. Natl. Acad. Sci. U.S.A.

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“…PDFs of surface air temperature bandpass filtered to such longer time scales exhibit similar features. They are also seen in PDFs of unfiltered daily variations, to which the low-frequency variations contribute, both in the observations and simulations (Fischer and Schär 2009;Ruff and Neelin 2012;Huybers et al 2014;Loikith et al 2015).…”

Section: A Bandpass Filteringmentioning

confidence: 74%

“…This implies that for understanding how the frequency of even rare and large synoptic potential temperature variations changes with climate, at least for now it suffices to understand changes in the mean and variance of the PDFs. 5) On longer time scales (*25 days), PDFs of nearsurface potential temperature variations exhibit nonGaussian tails, as seen in recent studies of surface temperature variations (e.g., Ruff and Neelin 2012;Huybers et al 2014;Loikith et al 2015). PDFs with sub-Gaussian tails are especially prevalent and imply that nonlinear processes must be operating that damp large deviations relative to normal statistics.…”

Section: Summary and Discussionmentioning

confidence: 96%

“…An earlier examination of near-surface potential temperature variations in reanalysis data gave no indication that such strong mixing and non-Gaussian PDFs occur (Swanson and Pierrehumbert 1997), presumably because potential temperature in the mean varies on scales much larger than the mixing length, and near-surface air temperatures are strongly forced by the lower boundary. However, recent examinations of surface temperature variations that were not restricted to synoptic time scales but included longer time scales found significant departures from Gaussian statistics (e.g., Ruff and Neelin 2012;Huybers et al 2014;Loikith et al 2015).…”

Section: Observed Distribution Of Temperature Variationsmentioning

confidence: 99%

“…For example, land-atmosphere feedbacks may become important on longer time scales (e.g., Schär et al 2004;Seneviratne et al 2006Seneviratne et al , 2010Berg et al 2014). They and other feedback processes may account for the non-Gaussian tails of PDFs commonly seen when temperature variations with longer time scales are included (e.g., Ruff and Neelin 2012;Huybers et al 2014;Loikith et al 2015). Indeed, when potential temperature variations are not filtered, so that lower-frequency variations remain included, or if they are filtered to time scales longer than approximately 25 days, departures from Gaussianity become significant: PDFs of such lower-frequency variations often have sub-Gaussian tails (see appendix A for an example).…”

Section: Observed Distribution Of Temperature Variationsmentioning

confidence: 99%

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Physics of Changes in Synoptic Midlatitude Temperature Variability

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This paper examines the physical processes controlling how synoptic midlatitude temperature variability near the surface changes with climate. Because synoptic temperature variability is primarily generated by advection, it can be related to mean potential temperature gradients and mixing lengths near the surface. Scaling arguments show that the reduction of meridional potential temperature gradients that accompanies polar amplification of global warming leads to a reduction of the synoptic temperature variance near the surface. This is confirmed in simulations of a wide range of climates with an idealized GCM. In comprehensive climate simulations (CMIP5), Arctic amplification of global warming similarly entails a large-scale reduction of the near-surface temperature variance in Northern Hemisphere midlatitudes, especially in winter. The probability density functions of synoptic near-surface temperature variations in midlatitudes are statistically indistinguishable from Gaussian, both in reanalysis data and in a range of climates simulated with idealized and comprehensive GCMs. This indicates that changes in mean values and variances suffice to account for changes even in extreme synoptic temperature variations. Taken together, the results indicate that Arctic amplification of global warming leads to even less frequent cold outbreaks in Northern Hemisphere winter than a shift toward a warmer mean climate implies by itself.

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Heterogeneous warming of Northern Hemisphere surface temperatures over the last 1200 years

Tingley

Huybers

2015

JGR Atmospheres

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The relationship between the mean and spatial variability of Northern Hemisphere surface temperature anomalies over the last 1200 years is examined using instrumental and proxy records. Nonparametric statistical tests applied to 14 well-studied, annually resolved proxy records identify two centuries roughly spanning the Medieval Climate Anomaly as characterized by increased spatial variability relative to the preinstrumental baseline climate, whereas two centuries spanning the Little Ice Age are characterized by decreased spatial variability. Analysis of the instrumental record similarly indicates that the late and middle twentieth century warm intervals are generally associated with increased spatial variability. In both proxy and instrumental records an overall relationship between the first two moments is identified as a weak but significant positive correlation between time series of the spatial mean and spatial standard deviation of temperature anomalies, indicating that warm and cold anomalies are respectively associated with increased and reduced spatial variability. Insomuch as these historical patterns of relatively heterogeneous warming as compared with cooling hold, they suggest that future warming will feature increased regional variability.

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U.S. Daily Temperatures: The Meaning of Extremes in the Context of Nonnormality

Cited by 53 publications

References 45 publications

US daily temperature records past, present, and future

US daily temperature records past, present, and future

Physics of Changes in Synoptic Midlatitude Temperature Variability

Heterogeneous warming of Northern Hemisphere surface temperatures over the last 1200 years

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