Fig. 1: Climatological context of the April 2023 HW record-shattering in the western Mediterranean region.
From: Record-shattering 2023 Spring heatwave in western Mediterranean amplified by long-term drought
a 850-hPa temperature (°C, shading) and 500 hPa geopotential height (dm, contours) at 12UTC on 27 April 2023. b Percentile of daily soil moisture at 0–7 cm depth (originally, volumetric fraction) for the 27th of April 2023. White stippling shows areas with volumetric soil moisture lower than the 1st percentile. Percentiles were computed using the 1950–2022 reference period for March, April and May. The yellow box shows the area used to compute the regional time series of both the coupling metric and the soil moisture (see Data and Methods section), while the magenta point inside the box refers to the location of Córdoba (Spain), and the one outside, that of Marrakech (Morocco), both hotspots of the event. The most affected countries are identified with the ISO 3166-1 alpha-2 country codes. c Córdoba in-situ time series for daily 2 m maximum temperatures (Tx) from 1 March to 5 May (black line) along with the 1950–2022 Tx 5-day centred running mean (grey) and Tx 15-day centred running mean of the 99th percentile (dark red). Magenta stars denote the 4 consecutive records (25–28 April) and yellow segments show the difference between these new records and the previous ones for April. d Regional (averaged over the yellow box in Fig. 1b) Standard Precipitation and Evaporation Index (SPEI) for 1960–2023 time series for the 4th week of April based on 1-, 3-, 12- and 24-month time scales (dark red and yellow lines, respectively). Data source: ERA5 (a), ERA5-Land (b), AEMET (c), CSIC (d).
