The lodging of crops by tornadoes

Area of Science:

• Atmospheric Science
• Agricultural Science
• Fluid Dynamics

Background:

• Tornadoes cause significant crop damage, with fallen crop tracks extending hundreds of meters.
• Photographic evidence suggests low-speed tornado (EF0/EF1) crop lodging is mainly due to strong radial flow at the canopy surface, not circumferential flow.

Purpose of the Study:

• To develop a tornado model that simulates radial flow near the ground.
• To create a generalized lodging model predicting track widths and crop fall directions.
• To analyze the sensitivity of lodging width to various parameters and perform a risk analysis.

Main Methods:

• Developed a 3D Euler equation-compliant tornado model with ground-level radial flow.
• Integrated the tornado model into a generalized crop lodging model.
• Calculated lodging patterns (forward convergence and backward convergence) in a normalized parameter plane.

Main Results:

• Lodging width and crop fall direction are functions of normalized translational and lodging velocities.
• Two primary lodging patterns, forward convergence (FC) and backward convergence (BC), were identified and mapped.
• Model predictions closely resemble observed field patterns, validating the model's approach.

Conclusions:

• The developed model accurately simulates tornado-induced crop lodging patterns.
• The model provides insights into the relationship between tornado dynamics, crop properties, and lodging outcomes.
• Further analysis can inform risk assessment and agricultural preparedness for tornado events.