• Drought classifications are increasingly frequent in the American West.
• Climate variables used by the USDM also show significant trends.
• The USDM reflects climate change but raises monitoring questions.
• Trends challenge current drought management and resource allocation.

June 14, 2024 — Drought management is crucial for various sectors, including agriculture, water management, and energy production. The United States Drought Monitor (USDM) has been a key tool in this effort since 2000, providing weekly updates on drought conditions. A peer-reviewed research paper postulates that emerging trends complicate the interpretation of these updates, particularly in a changing climate.

In its summary of the paper, Psys.org writes, “[T]his critical diagnostic tool is also struggling to keep pace with climate change as longer and more persistent dry spells plague the American West and take an increasing toll on groundwater reserves and the Colorado River:”

Some key areas in the research, titled “Emergent Trends Complicate the Interpretation of the United States Drought Monitor (USDM),” include:

Key Climate Variables.

The USDM uses several climate variables to classify droughts, including precipitation, runoff, soil moisture, terrestrial water storage, vapor pressure deficit, and near-surface air temperature. Over the past 23 years, trends in these variables have shown that drought classifications are occurring more frequently than expected, especially in the American West.

Regional Variations.

The frequency of drought classifications varies significantly across the United States. The American West, in particular, has experienced a prolonged dry period. For example, some areas in California have spent up to 18% of the past 23 years in “exceptional drought” (D4) conditions, far exceeding the expected 2% frequency.

Implications for Drought Monitoring.

These trends indicate that the USDM is accurately capturing changes in the climate. However, they also raise important questions about how drought monitoring and management should adapt to these long-term trends. If current methods are not updated, drought classifications might not reflect the true severity and frequency of drought conditions.

Challenges in Drought Assessment.

The USDM relies on a mix of objective measures and expert judgment, making it challenging to interpret trends over time. As climate conditions change, the thresholds for different drought classifications might also need to be adjusted. This is essential to ensure that drought management strategies remain effective and resources are allocated efficiently.

Conclusion.

The increasing frequency of drought classifications in certain regions, particularly the American West, highlights the need for a reassessment of current drought monitoring practices. While the USDM provides valuable insights into drought conditions, its methodology must evolve to account for the changing climate. This will help ensure that drought management remains responsive and effective in mitigating the adverse impacts of droughts on various sectors.

Citation.

Li, Z., Smerdon, J. E., Seager, R., Siegert, N., & Mankin, J. S. (2024). Emergent Trends Complicate the Interpretation of the United States Drought Monitor (USDM). AGU Advances, 5(2), e2023AV001070. https://doi.org/10.1029/2023AV001070