[A-CG30] Extratropical oceans and atmosphere

[ACG30-10] Some further thoughts on atmospheric fronts and frontal air-sea interaction

*Rhys Parfitt¹, Evan Jones¹, Allison Wing¹ (1.Florida State University)

Keywords:Frontal air-sea interaction, Atmospheric fronts, Extra-tropical transition

In the mid-latitudes, atmospheric fronts are responsible for much of the day-to-day variability in the atmosphere, and can also explain the time-mean structure of many fields. Atmospheric frontal variability is closely coupled to the ocean via large gradients in air-sea heat flux that exist across them (a spatial scale matching the oceanic mesoscale). A novel example is provided highlighting the importance of this interaction for tropical cyclones undergoing extra-tropical transition in the North Atlantic, where SSTs in the week prior to their arrival are seen to influence their eventual fate. Additionally, the frontal structure of tropical cyclones that do transition appear to reflect the underlying ocean currents.

Additionally, some further results are presented characterizing the typical evolution of air-sea heat fluxes with the passage of mid-latitude atmospheric fronts. Dependent on location, cold (warm) frontal passages typically lead to increases (decreases) in air-sea heat fluxes of up to 50-200% within 0-12 hours. The associated cross-frontal flux gradients would be almost impossible to capture accurately without simultaneous atmospheric and oceanic measurements. The typical perturbation timescale associated with frontal passage also indicates that mid-latitude air-sea heat fluxes can generally always be considered as under atmospheric frontal influence.

The above results provide further evidence of the need to significantly expand our measurement capabilities for mid-latitude air-sea interaction.