Differences in the Hydrological Cycle and Sensitivity Between Multiscale Modeling Frameworks with and without a
Kuan-Man Xu1, Zhujun Li2, Anning Cheng3
1Climate Science Branch, NASA Langley Research Center, Hampton, VA.
Journal of Advances in Modeling Earth Systems
|April 19, 2021
Summary
This study compares two multiscale modeling frameworks (MMFs) to understand climate model spread. Differences in turbulence and cloud treatments explain variations in simulated precipitation sensitivity to warming.
Area of Science:
- Climate modeling
- Atmospheric science
- Hydrology
Background:
- Global climate models (GCMs) underestimate precipitation increase relative to moisture increase under warming.
- Understanding model spread in GCMs is crucial for accurate climate projections.
Purpose of the Study:
- To investigate differences in hydrological sensitivity between two multiscale modeling frameworks (MMFs).
- To attribute these differences to distinct treatments of turbulence and low clouds.
- To inform the understanding of model spread in conventional GCMs.
Main Methods:
- Comparison of hydrological sensitivity and energetic constraints between two MMFs: SPCAM (without advanced turbulence closure) and SPCAM-IPHOC (with advanced turbulence closure).
- Analysis of differences in radiative cooling, Bowen ratio, and energy flux divergences.
Main Results:
- SPCAM-IPHOC shows higher slow-response and lower fast-response hydrological sensitivity than SPCAM.
- Differences between MMFs are comparable to the spread observed in conventional GCMs.
- Higher sensitivity in SPCAM-IPHOC linked to increased latent heating to radiative cooling ratio and decreased Bowen ratio; lower sensitivity in SPCAM linked to lack of low clouds and stronger cloud radiative cooling.
Conclusions:
- Turbulence and low cloud parameterizations significantly impact hydrological sensitivity in climate models.
- MMF differences highlight key processes contributing to GCM spread in precipitation response to warming.
- Further research into energy flux divergences is needed to explain land precipitation sensitivity differences.
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