Evaluation of precipitation and temperature numerical simulations for predicting erosion under climate change

Context

This internship is part of the project CLIMBAD (“CLIMate impact on BADland erosion”) which aims to predict future badland erosion under climate change. Badlands are places of intense erosion and key producers of sediment and carbon fluxes to the Mediterranean Sea. Badland erosion is driven by rainfall amount and intensity but is strongly reduced by vegetation cover. On the other hand, vegetation dynamics are sensitive to erosion and topographic features, and to rainfall and temperature changes. Badland erosion is also modulated by weathering that transforms bedrock into soil/regolith supplying erosion. Weathering, and particularly frost-weathering, is sensitive to climate and possibly vegetation. Predicting badland erosion under climate change therefore requires accounting for the coupling between vegetation and erosion on the one hand and the role of climate-dependent weathering on erosion on the other hand. The final objective of CLIMBAD is to provide new knowledge and tools concerning the future co-evolution of badland erosion and vegetation under climate change, which will help managers design appropriate mitigation strategies.

Objectives

The overall objective of the internship is to evaluate and guide the selection of appropriate precipitation and temperature scenarios to be used as forcings in the modeling framework developed in the project, later called CLIMBAD model. CLIMBAD model comprises a general landscape evolution model coupling vegetation dynamics, climate-dependent weathering, and erosion processes. It has been calibrated on catchments from the Draix-Bleone Critical Zone observatory (https://draixbleone.osug.fr/) based on long-term records (35 yrs) of rainfall, temperature, and sediment yield and vegetation trends extracted from aerial and satellite images.
The first objective will be to evaluate different simulations from the CNRM-AROME climate model over the past period (last 35 years) for Draix site, by comparing observed and simulated rainfall, temperature and sediment fluxes. The second objective will be to predict future sediment fluxes using the climate simulations as an input for the CLIMBAD model, and assess how they could differ, or not, from existing observed sediment fluxes.

Methods

The study will take advantage of existing simulations from the CNRM-AROME convection-permitting regional climate model (Caillaud et al., 2021). Convection Permitting Regional Climatic Models (CP-RCM) have been developed in recent years (Lucas-Pisher et al, 2021) to explicitly represent convective events, the intense and localized precipitation events being responsible for most flood and erosive events in the Mediterranean region.
The first step will be based on a long evaluation run of the CNRM-AROME over the period 1985-2020. This evaluation run is forced by a meteorological reanalysis and reproduces the chronology of the past meteorological events. Evaluation will rely on two criteria:

• Rainfall and temperature simulated by CP-RCM AROME will be compared with long-term observations from Draix-Bleone observatory (KIotz et al, 2023) and we will check that intense precipitation events are adequately reproduced (maximum intensity, accumulated rainfall, duration).
• AROME simulations will be used as input for CLIMBAD model, and the simulated sediment fluxes will be compared with long-term observed sediment fluxes from Draix-Bleone observatory. We will check that CLIMBAD model forced by AROME simulations can reproduce the chronology and magnitudes of sediment yields in the Laval catchment.

The second step will use a so-called “historical” run from the CP-RCM AROME where the CP RCM is forced by a global climate model following historical scenarios of greenhouse gases. Evaluation will rely on two criteria:

• Rainfall and temperature simulated by CP-RCM AROME will be compared with long-term observations from Draix-Bleone observatory. Because historical runs are not expected to reproduce the chronology of past events, we will compare the statistical properties of rainfall and temperature over the period.
• The climate simulations will be used to force CLIMBAD model, and the resulting simulated sediment fluxes will be compared with long-term observations. As for the rain and temperature, the comparison will be based on the statistical properties of sediment fluxes and not on the chronology.
  The third step, based on the evaluation from the two first steps, will consist in predicting future sediment fluxes by forcing the CLIMBAD model over future periods (2040-2049 and 2090-2099), under one or several climate scenarios. The predicted sediment fluxes will then be compared with actual sediment fluxes.

Required skills

Master in geosciences or applied mathematics. Strong programming abilities (e.g. with Python and/or R). Experience with the manipulation of large datasets.

Period of the internship

Ideally February-July (6 months).

Gratification

Around 570 euros per month.

Address

INRAE - Grenoble
2, rue de la papeterie, 38402 Saint-Martin-d’Hères.

Supervision:

Guillaume Evin (guillaume.evin inrae.fr) and Caroline Le Bouteiller (caroline.le-bouteiller inrae.fr)

References

• C. Caillaud et al., « Modelling Mediterranean heavy precipitation events at climate scale: an object-oriented evaluation of the CNRM-AROME convection-permitting regional climate model », Clim Dyn, vol. 56, no 5, p. 1717 1752, mars 2021, doi: 10.1007/s00382-020-05558-y.
• Carriere, A., Le Bouteiller, C. Tucker, G. E., Klotz, Klotz, Klotz, S. , Naaim, M. (2020) Impact of vegetation on erosion: Insights from the calibration and test of a landscape evolution model in alpine badland catchments. Earth Surf. Process. Landforms, 45: 1085– 1099. https://doi.org/10.1002/esp.4741
• Coppola, E., S. Sobolowski, E. Pichelli, F. Raffaele, B. Ahrens, I. Anders, N. Ban, et al. (2020). A First-of-Its-Kind Multi-Model Convection Permitting Ensemble for Investigating Convective Phenomena over Europe and the Mediterranean. Climate Dynamics 55 (1): 3–34. https://doi.org/10.1007/s00382-018-4521-8
• S. Klotz et al., « A high-frequency, long-term data set of hydrology and sediment yield: the alpine badland catchments of Draix-Bléone Observatory », Earth System Science Data, vol. 15, no 10, p. 4371 4388, oct. 2023, doi: 10.5194/essd-15-4371-2023.
• Lucas-Picher, P., Argüeso, D., Brisson, E., Tramblay, Y., Berg, P., Lemonsu, A., Kotlarski, S., and Caillaud, C. (2021). Convection-permitting modeling with regional climate models: Latest developments and next steps. Wiley Interdis. Reviews: Climate Change, 12(6), e731. https://doi.org/10.1002/wcc.731