08 Jun 2023
 | 08 Jun 2023

Identification of compound drought and heatwave events on a daily scale and across four seasons

Baoying Shan, Niko E. C. Verhoest, and Bernard De Baets

Abstract. Compound drought and heatwave (CDHW) events can incur intensified damage to ecosystems, economies, and societies, especially on a warming planet. Although it has been reported that CDHW events in the winter season can also affect insects, birds, and wildfires, the literature generally focuses on the summer season exclusively. Moreover, the coarse resolution of droughts as determined on a monthly scale may hamper a precise identification of the start and/or end dates of CDHW events. Therefore, we propose a method to identify CDHW events on a daily scale that is applicable across the four seasons. More specifically, we use standardized indices calculated on a daily scale to identify four types of compound events in a systematic way. Based on the hypothesis that droughts or heatwaves should be statistically extreme and independent, we remove minor dry or warm spells and merge mutually dependent ones. To demonstrate our method, we make use of 120 years of daily precipitation and temperature observed at Uccle, Brussels-Capital Region, Belgium. Our method yields more precise start and end dates for droughts and heatwaves than what can be obtained with a classical approach acting on a monthly scale, thus also allowing for a better identification of CDHW events. Consistent with existing literature, we find an increase in the occurrence of the number of days in CDHW events at Uccle, mainly due to the increasing frequency of heatwaves. Our results also reveal a seasonality of CDHW events as droughts and heatwaves are negatively dependent in the winter season at Uccle, while they are positively dependent in the other seasons. Overall, the method proposed in this study is shown to be robust and shows potential for exploring how year-round CDHW events influence ecosystems.

Baoying Shan et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-147', Anonymous Referee #1, 10 Jul 2023
    • AC1: 'Reply on RC1', Baoying Shan, 17 Sep 2023
  • RC2: 'Comment on egusphere-2023-147', Anonymous Referee #2, 12 Jul 2023
    • AC2: 'Reply on RC2', Baoying Shan, 17 Sep 2023

Baoying Shan et al.


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Short summary
This study developed a convenient and new method to identify the occurrence of droughts, heatwaves, and co-occurring droughts and heatwaves across four seasons. From that, we could know the drought (or heatwave) starts on which day and ends on which day. We found an increase in the frequency of heatwaves and the co-occurring droughts and heatwaves in Belgium caused by climate change. We also found that different months have different chances of co-occurring droughts and heatwaves.