Hai is a Postdoctoral Researcher at the GFI and BCCR.
This study investigates the direct and indirect effects of the absolute SST and SST gradient on the development of extratropical cyclones through sensible and latent heat fluxes using an idealized moist channel model. The model is initialized with a zonal wind field resembling the midlatitude jet and a different SST distribution for each experiment, where both the strength and position of the SST gradient are varied. The surface latent heat flux associated with the absolute SST plays a key
role in enhancing the moist baroclinic development, while the sensible heat fluxes associated with the SST gradient play a minor role which can be detrimental for the development of the cyclone. The additional moisture provided by the latent heat fluxes can originate from about 1000 km ahead of the cyclone a day prior to the time of the most rapid deepening. When the SST in this region is higher than 16 degrees Celcius, the additional latent heat is conducive to explosive cyclone development. For SSTs above 20 degrees Celcius, the cyclones feature characteristics of hybrid cyclones with latent heat release close to their core and maintain their intensity for a longer period due to continuous and extensive moisture supply from the surface. Our study emphasizes the role of the absolute SST compared to the SST gradient on the deepening of cyclones, which can play an important role in the
frequent occurrence of explosive cyclones over the warm ocean surface. For longer time scales, our result suggests that the absolute SST most likely plays a role in the modification of the storm tracks."
Time: March 9, at 14:15. Place: BCCR lecture room 4020, Jahnebakken 5.