Research ArticleCLIMATOLOGY

A century of observations reveals increasing likelihood of continental-scale compound dry-hot extremes

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Science Advances  23 Sep 2020:
Vol. 6, no. 39, eaaz4571
DOI: 10.1126/sciadv.aaz4571
  • Fig. 1 Nonparametric Mann-Kendall trend analysis.

    Red shaded areas show a statistically significant increase (at the 5% level) in the return period level of (A) dry extremes, (B) hot extremes, and (C) concurrent dry AND hot extremes across CONUS over the past 122 years (1896–2017) at the annual scale. Fraction of area in each region and the entire CONUS with significant trends are also shown in the figure.

  • Fig. 2 Frequency of compound dry-hot extremes has increased.

    (A to C) Frequency of >25-year, (D to F) frequency of >50-year, and (G to I) frequency of >75-year bivariate dry AND hot extremes across CONUS in the periods of 1943–1967 (A, D, and G), 1968–1992 (B, E, and H), and 1993–2017 (C, F, and I).

  • Fig. 3 Number of climate divisions affected by compound dry-hot extremes is increasing across many regions.

    (A to G) Different regions of CONUS affected by >25-year univariate dry, univariate hot, and bivariate dry AND hot extremes. (H to J) Entire CONUS affected by >25-year, >50-year, and >75-year extremes, between 1896 and 2017.

  • Fig. 4 Impacted areas by >25-year compound dry-hot extremes are enlarging.

    Slope of linear regression to the spatial extent of >25-year univariate dry, univariate hot, and bivariate dry AND hot extremes based on the affected area size (km2). Filled circles are associated with statistically significant trends at the 10% level, and empty circles are associated with trends that are not statistically significant at the 10% level. None of the increases are significant at the 5% level. Boxes represent the range between the 25th and 75th percentiles of the linear regression slopes, and the horizontal line in each box corresponds to the slopes’ median.

  • Fig. 5 Spatial homogeneity for compound dry-hot extremes is increasing.

    Slope of linear regression to time series of Moran’s I of >25-year univariate dry, univariate hot, and bivariate dry AND hot extremes for different climate regions (A to G) as well as the entire CONUS (H) over the past 122 years (1896–2017).

Supplementary Materials

  • Supplementary Materials

    A century of observations reveals increasing likelihood of continental-scale compound dry-hot extremes

    Mohammad Reza Alizadeh, Jan Adamowski, Mohammad Reza Nikoo, Amir AghaKouchak, Philip Dennison, Mojtaba Sadegh

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    • Tables S1 to S5
    • Figs. S1 to S17

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