Chaqdid et al. (2026) Toward Reducing Uncertainty in Simulating Temporal Clustering of Extreme Precipitation in Morocco: Insights from High-Resolution GCMs

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Identification

Journal: Journal of Climate
Year: 2026
Date: 2026-01-29
Authors: Abdelaziz Chaqdid, Alexandre Tuel, abdelouahad El Fatimy, Nabil El Moçayd
DOI: 10.1175/jcli-d-25-0138.1

Research Groups

Not explicitly mentioned in the abstract.

Short Summary

This study develops a process-based framework to characterize the climatology and drivers of temporal clustering of extreme precipitation (TCEP) in Morocco and evaluates its representation in CMIP6 HighResMIP models, finding TCEP is significant in Morocco driven by atmospheric circulation anomalies, but models underestimate total episode rainfall.

Objective

To develop a process-based framework for detecting and diagnosing temporal clustering of extreme precipitation (TCEP) in Morocco.
To characterize the climatology and atmospheric drivers of TCEP in Morocco.
To evaluate the representation of TCEP in six CMIP6 High-Resolution Model Intercomparison Project (HighResMIP) models.

Study Configuration

Spatial Scale: Morocco, specifically northwestern and southeastern regions, at a resolution of 0.1°.
Temporal Scale: 1979–2025 for data analysis; TCEP episodes defined within a 21-day moving window; peak season from November to April.

Methodology and Data

Models used: Multisource Weighted-Ensemble Precipitation (MSWEP), ERA5 reanalysis, six CMIP6 High-Resolution Model Intercomparison Project (HighResMIP) models (e.g., FGOALS-f3-H, MPI-ESM1-2-XR, HiRAM-SIT-HR, BCC-CSM2-HR).
Data sources: MSWEP (0.1°), ERA5 reanalysis, CMIP6 HighResMIP model simulations. TCEP detection used a nonparametric, count-based approach identifying daily exceedances of the 99th-percentile threshold for extreme precipitation events (EPEs). Drivers diagnosed from composites of atmospheric anomalies filtered with the false discovery rate (FDR). Statistical significance assessed via bootstrap resampling.

Main Results

TCEP is statistically significant in northwestern and southeastern Morocco.
TCEP episodes peak from November to April.
Individual extreme precipitation events (EPEs) within TCEP episodes can reach up to 283 mm, representing approximately 47%–99% of the mean annual total.
TCEP episodes can include up to four EPEs.
In northwestern Morocco, TCEP is associated with enhanced westerly integrated vapor transport (IVT), frequent atmospheric river (AR) landfalls, a quasi-stationary trough over the eastern North Atlantic–Iberia, and an equatorward-displaced jet, often during negative North Atlantic Oscillation (NAO) phases.
In southeastern Morocco, atmospheric anomalies are weaker, and orographic forcing plays a larger role.
HighResMIP models reproduce EPE counts per episode but underestimate total episode rainfall by up to 52%.
A clustering simulation skill index (CSSI) ranked FGOALS-f3-H, MPI-ESM1-2-XR, and HiRAM-SIT-HR highest, and BCC-CSM2-HR lowest across all regions.
Comparisons between coupled ocean–atmosphere and AMIP-style simulations indicate that ocean coupling is an important source of TCEP bias in models.

Contributions

Development of a novel process-based framework for detecting and diagnosing temporal clustering of extreme precipitation (TCEP).
Comprehensive characterization of TCEP climatology and its atmospheric drivers in Morocco, an area where this phenomenon was previously poorly characterized.
First evaluation of CMIP6 HighResMIP models' ability to represent TCEP in Morocco, identifying specific biases related to rainfall magnitude and the role of ocean coupling.

Funding

Not explicitly mentioned in the abstract.

Citation

@article{Chaqdid2026Toward,
  author = {Chaqdid, Abdelaziz and Tuel, Alexandre and Fatimy, abdelouahad El and Moçayd, Nabil El},
  title = {Toward Reducing Uncertainty in Simulating Temporal Clustering of Extreme Precipitation in Morocco: Insights from High-Resolution GCMs},
  journal = {Journal of Climate},
  year = {2026},
  doi = {10.1175/jcli-d-25-0138.1},
  url = {https://doi.org/10.1175/jcli-d-25-0138.1}
}

Original Source: https://doi.org/10.1175/jcli-d-25-0138.1