Fazli et al. (2025) Quantifying single, compound and cascading climate extremes: Implications for agricultural resilience in California

Identification

• Journal: Agricultural and Forest Meteorology
• Year: 2025
• Date: 2025-10-18
• Authors: Shahryar Fazli, Wenzhao Li, Rejoice Thomas, Surendra Maharjan, Mohammad Sina Jahangir, André Daccache, Hesham Morgan, Mohamed Allali, Hesham El‐Askary
• DOI: 10.1016/j.agrformet.2025.110890

Research Groups

• Earth Systems Science and Data Solutions Lab, Chapman University, Orange, CA, USA
• Schmid College of Science and Technology, Chapman University, Orange, CA, USA
• Department of Biological and Environmental Engineering, Cornell University, Ithaca, USA
• Department of Biological and Agricultural Engineering, University of California Davis, Davis, CA, USA
• Department of Geology, Faculty of Science, Cairo University, Giza, Egypt
• Fowler School of Engineering, Chapman University, Orange, CA, USA
• Department of Environmental Sciences, Faculty of Science, Alexandria University, Alexandria, Egypt

Short Summary

This study quantifies the spatiotemporal dynamics of single, compound, and cascading climate extremes in California's Central Valley from 1951 to 2025, revealing increasing heatwaves and droughts, northward shifting hotspots, and differential vulnerability for almonds and grapes, which informs agricultural resilience strategies.

Objective

• To identify the relation between extreme events and vegetation dynamics for key crops.
• To evaluate spatial and temporal trends of those events using robust statistical techniques.
• To assess the impact of those extreme events on the agricultural sector and across phenological stages.

Study Configuration

• Spatial Scale: California's Central Valley (approximately 47,000 square kilometers), gridded data at 1/24° (approximately 4 km) resolution.
• Temporal Scale: Long-term (1951–2025), mid-term (1981–2025), and vegetation dynamics (2000–2020). Daily, 16-day, monthly, and yearly analyses.

Methodology and Data

• Models used: Mann-Kendall test, Theil-Sen median slope, Wavelet analysis, Standardized Precipitation Index (SPI), Standardized Temperature Index (STI), kernel Normalized Difference Vegetation Index (kNDVI), Heatwave Magnitude Index (HWMI), Coldwave Magnitude Index (CWMI), Drought Magnitude Index (DRMI), Excessive Rainfall Magnitude Index (ERMI), Compound Extreme Magnitude Index (CEMI), Cascading Event Magnitude Index (CAEMI).
• Data sources: NOAA nClimGrid-Daily (daily maximum temperature (TMAX), minimum temperature (TMIN), precipitation (Pre)), MODIS MOD13A2 V6.1 (Normalized Difference Vegetation Index (NDVI)), USDA Cropland Data Layer (CDL), USDA National Agricultural Statistics Service (NASS) (crop production, area harvested, yield), PRISM (monthly vapor pressure deficit (VPD)), MODIS MOD16A2.061 (monthly evapotranspiration (ET)), GRACE and GRACE-FO (monthly water equivalent thickness), NOAA National Centers for Environmental Information (NCEI) (Pacific Decadal Oscillation (PDO) and El Niño 3.4 indices).

Main Results

• Heatwave (HW) and drought (DR) events are increasing, particularly in the southern Central Valley (CV), with 35% and 60% of the region showing strong upward trends in HW frequency and intensity (mid-term), respectively, linked to a warming trend of +0.234 °C per decade.
• The northern CV (Tehama to Sacramento Counties) exhibits greater vulnerability to excessive rainfall (ER), coldwave-drought (CWDR), and coldwave-excessive rainfall (CWER) events, reflecting heightened climate variability.
• Hotspots of climate extremes are shifting northward, with HWDR migrating at a rate of 20.94 km per decade.
• June–July HW and DR peaks coincide with critical crop stages for almonds and grapes, while February–March rainfall supports early vegetation growth.
• Almonds showed the highest vulnerability to drought, experiencing severe kNDVI anomaly drops in 2014, whereas grapes responded moderately to heat and benefited from early rain, reaching a kNDVI anomaly peak of 0.03 in 2005.
• Intra-annual analysis for 2014 revealed that extreme HW and DR, combined with low rainfall and groundwater decline, intensified stress during critical almond hull split and fruit set stages.
• Compound and cascading events impose considerably greater stress on agroecosystems than single extremes, with HWDR events peaking from late spring to mid-summer.

Contributions

• Provides the first integrated assessment of single, compound, and cascading climate extremes in California's Central Valley over approximately a 75-year period at fine spatial scales (4 km resolution).
• Explicitly links hotspot migration and land-use contrasts to crop phenology (almonds and grapes), offering agricultural diagnostics directly relevant to management.
• Advances the understanding of climate–agriculture linkages and supports resilient planning in one of the world’s most productive farming regions.

Funding

• US Department of Education award number P116Z220190, “Earth Systems Science and Data Solutions Lab (EssDs): Applying Data Science Techniques to Achieve the UN Sustainable Development Goals”.

Citation

@article{Fazli2025Quantifying,
  author = {Fazli, Shahryar and Li, Wenzhao and Thomas, Rejoice and Maharjan, Surendra and Jahangir, Mohammad Sina and Daccache, André and Morgan, Hesham and Allali, Mohamed and El‐Askary, Hesham},
  title = {Quantifying single, compound and cascading climate extremes: Implications for agricultural resilience in California},
  journal = {Agricultural and Forest Meteorology},
  year = {2025},
  doi = {10.1016/j.agrformet.2025.110890},
  url = {https://doi.org/10.1016/j.agrformet.2025.110890}
}