Seasonal land-heating vorticity tendency

Heating over land often favours a deeper cyclonic thermal low, while cooling favours a shallower anticyclonic thermal high. Diabatic heating and surface friction violate the assumptions of simple parcel PV conservation; a vertical profile is needed for a quantitative statement.

Table of contents
- Coastal vorticity tendency from variable surface drag Seasonal land-heating vorticity tendency

Coastal vorticity tendency from variable surface drag ( $[\nabla \times (- r u)]_{z} = - r ζ - (\nabla r \times u)_{z}$ )

 0  0

Spatially varying drag has a vorticity tendency beyond simple damping of existing relative vorticity. The cross-gradient term depends on wind direction and the gradient of surface resistance. Increasing roughness on moving from ocean to land does not alone specify a universal cyclonic or anticyclonic sign. Seasonal heating also changes stratification and isentropic mass thickness, so it cannot generally be replaced by adiabatic PV conservation.