A Moist Potential Vorticity Model for Midlatitude Long-Lived Mesoscale Convective Systems over Land

Journal Article · Mon Oct 09 00:00:00 EDT 2023 · Journal of the Atmospheric Sciences

DOI:https://doi.org/10.1175/jas-d-22-0244.1· OSTI ID:2329271

Yang, Qiu ^[1]; Leung, Lai-Yung Ruby ^[1]; Feng, Zhe ^[1]; Chen, Xingchao ^[2]

---

1. Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
2. Pennsylvania State Univ., University Park, PA (United States)

Mesoscale convective systems (MCSs) bring large amounts of rainfall and strong wind gusts to the midlatitude land regions, with significant impacts on local weather and hydrologic cycle. However, weather and climate models face a huge challenge in accurately modeling the MCS life cycle and the associated precipitation, highlighting an urgent need for a better understanding of the underlying mechanisms of MCS initiation and propagation. From a theoretical perspective, a suitable model to capture the realistic properties of MCSs and isolate the bare-bones mechanisms for their initiation, intensification, and eastward propagation is still lacking. To simulate midlatitude MCSs over land, we develop a simple moist potential vorticity (PV) model that readily describes the interactions among PV perturbations, air moisture, and soil moisture. Multiple experiments with or without various environmental factors and external forcing are used to investigate their impacts on MCS dynamics and mesoscale circulation vertical structures. The result shows that mechanical forcing can induce lower-level updraft and cooling, providing favorable conditions for MCS initiation. A positive feedback among surface winds, evaporation rate, and air moisture similar to the wind-induced surface heat exchange over tropical ocean is found to support MCS intensification. Both background surface westerlies and vertical westerly wind shear are shown to provide favorable conditions for the eastward propagation of MCSs. Last, our result highlights the crucial role of stratiform heating in shaping mesoscale circulation response. In conclusion, the model should serve as a useful tool for understanding the fundamental mechanisms of MCS dynamics.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 2329271
• Report Number(s): PNNL-SA--188085
• Journal Information: Journal of the Atmospheric Sciences, Journal Name: Journal of the Atmospheric Sciences Journal Issue: 10 Vol. 80; ISSN 0022-4928
• Publisher: American Meteorological Society
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
Atmosphere-land interaction
Convection
Idealized models
Mesoscale convective system
Mesoscale systems
Moisture/moisture budget
Potential vorticity