How day-night (diurnal) heating changes affect the dynamics of hurricanes using a linear model.

What is it about?

Discusses how day-night (diurnal) heating changes affect tropical cyclones (hurricanes) using a linear model. Specifically it focuses on where in a hurricane the response is balanced, and where the response radiates as a wave. We find that diurnal heating in the eyewall produces a response confined near to the eyewall. Diurnal heating in the cirrus canopy produces a response everywhere in the hurricane. Diurnal responses can only start to radiate as a true wave hundreds of km from the vortex center. Therefore, diurnal responses to heating in hurricanes is primarily balanced, instead of radiating as a wave.

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Photo by NASA on Unsplash

Photo by NASA on Unsplash

Why is it important?

This work follows from previous studies on the diurnal cycle in hurricanes, namely Dunion (2014), Navarro & Hakim (2016), Navarro et al. (2017), and O'Neill et al. (2017). These works illustrated (a) that a diurnal cycle exists in the cirrus canopy, (b) how this heating affects the dynamics of hurricanes. Our study is unique in that it uses a heavily simplified linear model to show that the dynamical response can still be captured in a linear framework. It also suggests that the diurnal cycle in the cirrus canopy affects the dynamics in the outer parts of a hurricane more than the diurnal cycle in the eyewall. It also shows that the pulse Dunion (2014) observed in the cirrus canopy may originate in the cirrus canopy itself, as opposed to the eyewall.