North American Hydroclimate Variability

Last updated: February 20, 2026

The North American Monsoon (NAM) delivers critical summer rainfall to northwestern Mexico and the southwestern United States, supporting regional ecosystems, water resources, and agriculture. Its strength and geographic extent are shaped by interactions between land–sea temperature contrasts, atmospheric circulation, and complex topography. Understanding how the NAM responds to climate change is therefore essential for anticipating future hydroclimate in this vulnerable region. Past warm periods, such as the Last Interglacial, offer valuable opportunities to study how the monsoon behaves under climates warmer than today, but both paleoclimate proxy records and climate models provide an incomplete and sometimes inconsistent picture of its past variability.

My research combines paleoclimate reconstructions and climate model analysis to better understand the dynamics of the North American Monsoon and its sensitivity to climate forcing. Using geochemical proxy records from marine sediments, I investigate how monsoon rainfall and regional hydroclimate responded to glacial–interglacial climate changes, helping to establish observational constraints on its natural variability. These records provide an important benchmark for evaluating climate model simulations and for understanding how the monsoon may respond to future warming.

Complementing this proxy work, I investigate why climate models struggle to accurately simulate the NAM. In particular, I focus on how biases in the representation of topography—and how these biases evolve with increasing model resolution—affect simulated monsoon circulation and rainfall patterns. Through analysis of multi-model simulations and targeted sensitivity experiments, this work identifies topographic representation as a key driver of persistent model errors in monsoon rainfall. Together, this research helps bridge gaps between proxy evidence and model simulations, improving our understanding of monsoon dynamics and strengthening confidence in projections of future hydroclimate in western North America.

RELATED PUBLICATIONS:

• Meegan-Kumar, D., Tierney, J. E., Bhattacharya, T., Lofverstrom, M., Zhu, J., & Murray, J. W. (in prep). Response of the North American Monsoon to glacial--interglacial climate forcings. For submission to Paleoceanography & Paleoclimatology

• Meegan-Kumar, D., Baldwin, J. W. (in prep) Topography Shapes Distinct Patterns of North American Monsoon Rainfall Biases with Increasing Earth System Model Resolution. For submission to AGU Advances