Unlocking Coherent Patterns of Land Hydroclimate Changes and Some New Insights on Heatwave Events

Speaker: Suqin Duan
Institution: UCLA
Location: 7124A
Date: January 18, 2024
Time: 3:30 pm to 4:30 pm


Energetic, thermodynamic and dynamic constraints dictate the first principles of global mean hydroclimate changes. However, the implications for land hydroclimate are complicated by soil moisture limitations and heterogeneous surface properties. In this talk, I will first present a process-oriented phase space structured around daily soil moisture and climatological aridity index. Transforming the geographical space to this novel phase space brings divergent model predictions to similar patterns, and allows for interpretation of local, daily mechanistic relationships between key hydroclimatic variables in the context of time-mean global-mean energetic constraints and the wet-get-wetter/dry-get-drier paradigm. The patterns also accentuate the sensitivity of temperature extremes to soil moisture limitation.

Next, I will present a case study of the 2021 Pacific Northwest Heatwave where we constrain the atmospheric circulation in CESM2 to follow observations and examine across 100 ensemble members that have different initial land surface conditions. I will discuss the impact of atmospheric circulation and soil moisture on this heatwave.

Third, I will talk about moist heatwaves in the tropics. It has been postulated that the onset of deep convection and precipitation arising from hot and humid near-surface air limits the extent of moist heatwaves. We instead find critical yet underappreciated impact from the entrainment of sub-saturated air in the lower free troposphere. I will discuss its regional implications and climate changes.