Mega-heatwave temperatures due to combined soil desiccation and atmospheric heat accumulation

Journal name:
Nature Geoscience
Volume:
7,
Pages:
345–349
Year published:
DOI:
doi:10.1038/ngeo2141
Received
Accepted
Published online

The recent European mega-heatwaves of 2003 and 2010 broke temperature records across Europe1, 2, 3, 4, 5. Although events of this magnitude were unprecedented from a historical perspective, they are expected to become common by the end of the century6, 7. However, our understanding of extreme heatwave events is limited and their representation in climate models remains imperfect8. Here we investigate the physical processes underlying recent mega-heatwaves using satellite and balloon measurements of land and atmospheric conditions from the summers of 2003 in France and 2010 in Russia, in combination with a soil–water–atmosphere model. We find that, in both events, persistent atmospheric pressure patterns induced land–atmosphere feedbacks that led to extreme temperatures. During daytime, heat was supplied by large-scale horizontal advection, warming of an increasingly desiccated land surface and enhanced entrainment of warm air into the atmospheric boundary layer. Overnight, the heat generated during the day was preserved in an anomalous kilometres-deep atmospheric layer located several hundred metres above the surface, available to re-enter the atmospheric boundary layer during the next diurnal cycle. This resulted in a progressive accumulation of heat over several days, which enhanced soil desiccation and led to further escalation in air temperatures. Our findings suggest that the extreme temperatures in mega-heatwaves can be explained by the combined multi-day memory of the land surface and the atmospheric boundary layer.

At a glance

Figures

  1. Summer soil moisture-temperature coupling during 1980-2011 in Europe.
    Figure 1: Summer soil moisture–temperature coupling during 1980–2011 in Europe.

    Maximum value of the π daily coupling metric10 per 0.25° latitude for the months from June to August. The 2003 and 2010 mega-heatwaves are indicated by red arrows.

  2. Air temperature and soil moisture in Europe during recent mega-heatwave summers.
    Figure 2: Air temperature and soil moisture in Europe during recent mega-heatwave summers.

    ad, Data for 10-day pre-heatwave (23 July–1 August) and mega-heatwave (4–13 August) periods in 2003: average afternoon near-surface air temperature19 (T, K) and mean sea-level pressure19 (hPa) (a); anomalies in surface soil moisture30 (ω′), expressed in the number of standard deviations (σ) (b); co-variability of the T anomalies (T′,σ) and the anomalies in the contribution of soil moisture deficit to the surface sensible heat flux20 (e′,σ) (c); and evolution of T′ and e′ for an area of 200 km radius around Trappes (marked in ac) (d). Rn is surface net radiation, λE is latent heat flux and λEp is latent heat flux based on potential evaporation. eh, Same as ad but for a 10-day pre-heatwave (1–10 July) and mega-heatwave (1–10 August) period in 2010; the focus region in h is the 200 km radius around Voronezh (marked in eg). The horizontal black lines in d and h indicate the mean Bowen ratio ±1σ for each 10-day period.

  3. ABL conditions during recent mega-heatwaves.
    Figure 3: ABL conditions during recent mega-heatwaves.

    a, Representative night-time (00Z) soundings of potential temperature (θ) from Trappes in 2003 (triangles) and Voronezh in 2010 (circles), during pre-heatwave (blue) and mega-heatwave (orange) periods. Solid lines indicate model initial conditions. b, Same but for the afternoon (12Z). c, Multi-day evolution of the afternoon θ profiles from Voronezh (2010). Black contours at 1.2 K km−1 indicate θ gradients; the white dashed line illustrates the multi-day increase in ABL height. de, Sensitivity of the ABL to soil moisture content and heat advection using the mega-heatwave (d) and pre-heatwave (e) initial conditions. Lines represent Bowen ratios (white), heat entrainment (blue, W m−2) and ABL heights (black dashed, m); shading indicates afternoon ABL θ.

  4. Land-atmosphere interactions during mega-heatwaves revisited.
    Figure 4: Land–atmosphere interactions during mega-heatwaves revisited.

    Representation of the main soil moisture–air temperature interactions in the development of a mega-heatwave. Red and blue arrows represent positive and negative correlations, respectively.

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Author information

Affiliations

  1. School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, United Kingdom

    • Diego G. Miralles
  2. Laboratory of Hydrology and Water Management, Ghent University, B-9000 Ghent, Belgium

    • Diego G. Miralles
  3. Hydrology and Quantitative Water Management Group, Wageningen University, 6709PA Wageningen, The Netherlands

    • Adriaan J. Teuling
  4. Max Planck Institute for Meteorology, 20146 Hamburg, Germany

    • Chiel C. van Heerwaarden
  5. Meteorology and Air Quality Section, Wageningen University, 6709PA Wageningen, The Netherlands

    • Jordi Vilà-Guerau de Arellano

Contributions

D.G.M., A.J.T. and J.V-G.d.A. jointly designed the study. D.G.M. led the large-scale analyses, A.J.T. the study of the sounding profiles, and J.V-G.d.A. the model experiments. C.C.v.H. contributed to the development of the atmospheric model. All co-authors contributed to the writing of the manuscript and the discussion and interpretation of results.

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The authors declare no competing financial interests.

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