EGU2020-7719
https://doi.org/10.5194/egusphere-egu2020-7719
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Identification of droughts and heatwaves in the Western Mediterranean, variability and impacts on vegetation and wildfires using the coupled ORCHIDEE-WRF regional model

Antoine Guion1, Solène Turquety2, Jan Polcher3, Romain Pennel4, and Lluis Fita5
Antoine Guion et al.
  • 1Sorbonne Université, Faculté des sciences, Laboratoire de Météorologie Dynamique (LMD), IPSL, France
  • 2Sorbonne Université, Faculté des sciences, Laboratoire de Météorologie Dynamique (LMD), IPSL , France
  • 3CNRS, Ecole Polytechnique, Laboratoire de Météorologie Dynamique (LMD), IPSL , France
  • 4Université Paris-Saclay, Ecole Polytechnique, Laboratoire de Météorologie Dynamique (LMD), IPSL , France
  • 5Universidad de Buenos Aires, CONICET, Centro de Investigaciones del Mar y la Atmosfera (CIMA), UMI, Argentina

In line with what is expected in a context of global warming, droughts and heatwaves have increased both in frequency and intensity over the last century. Severe wildfires and vegetation depletion can result from those extreme weather events with considerable economic, social and environmental damages.

For the development of mitigation and adaptation strategies, there is a need for exhaustive vulnerability assessments, including the impacts of droughts and heatwaves on the Mediterranean environment.

If heatwave characteristics are well documented, similar studies about droughts are partial. Most of them are focused on meteorological droughts while agronomical ones are more complex to identify.

 

Using a coupled land surface–atmosphere regional model (ORCHIDEE-WRF) with the integration of plant phenology, we present an analysis of droughts and heatwaves occurring in the Western Mediterranean over the last 40 years. These extreme events are identified using two complementary methods: the Percentile Limit Anomalies (PLA) and the Standardized Precipitation Evapotranspiration Index (SPEI).

Impact assessment analysis show significant and dominant effect of droughts on plant phenology during summer. Evaluated using the Leaf Area Index (LAI), plant depletion can reach more than 50%. Response to drought depends on the vegetation type (long vs short root system) and biome (temperate vs semi-arid).

The impact of these extreme events on fire risk will be presented based on calculations of the wildfire meteorological risk (Fire Weather Index) and an analysis of the fire activity observed by the MODIS satellite instrument. We show that, even if extreme high temperature is the dominant cause, drought contributes to an increase of risk. Simultaneous heatwaves and droughts are the worst environmental conditions. The observed burned area can be ±4 times greater than during non-extreme conditions and the fire duration ±0.25 times longer.

How to cite: Guion, A., Turquety, S., Polcher, J., Pennel, R., and Fita, L.: Identification of droughts and heatwaves in the Western Mediterranean, variability and impacts on vegetation and wildfires using the coupled ORCHIDEE-WRF regional model, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7719, https://doi.org/10.5194/egusphere-egu2020-7719, 2020

Comments on the presentation

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Presentation version 1 – uploaded on 07 Apr 2020
  • CC1: Comment on EGU2020-7719, Francisco Pastor, 29 Apr 2020

    Dear Antoine, congratulations for your work. I think it is interesting to evaluate the impact of heatwaves and droughts on vegetation and wildfires. We assume there is an impact but it is good to put some figures explaining such impact.

    I just have a question, in slide 7 you say "Droughts last longer (39 days on average) than heatwaves (18 days)". There is still a debate on the definition of a heatwave (the number of consecutive days, temperature percentiles exceeded, impacts on public health), how do you define a heatwave? 75 percentile from the first day? This 18 days duration is a global Med average or local/regional event?

    Thanks and best regards

    • AC1: Reply to CC1, Antoine Guion, 30 Apr 2020

      Dear Francisco,

      Thank you for your consideration.

      Indeed, the definition of heatwave and drought is often discussed, especially the latter one as it depends on its type (meteorological, hydrological and agricultural).

      I did not precise all the required conditions on the slide 5 explaining the indicators. Inspired from Lhotka and Kysely (2015), the 3-day minimum duration is applied in our analysis. It means that we define a heatwave/drought event as at least three consecutive hot/dry days (positive anomalies from the 75 percentile).

      Applying those criteria to both extreme events, soil dryness conditions last longer than extreme high temperature conditions. The 18 days duration is averaged at the Mediterranean scale. We noticed that it can be higher at the sub-regional scale.

      I hope it answers your question. I remain at your disposal for any other questions.

      Best regards,

      Antoine

      • CC2: Reply to AC1, Francisco Pastor, 04 May 2020

        Thank you very much for your answer Antoine