A Numerical Case Study of East Asian Coastal Cyclogenesis

Abstract

The relative importance of latent beat release and surface sensible heat flux in a case of East Asian coastal cyclogenesis were investigated by performing numerical experiments with the ECMWF limited-area model. In the control experiment that included all physical processes, the cyclone developed rapidly in a way similar to that observed. In the experiment without latent beat feedback, only a shallow low appeared when the upper short-wave trough approached the inverted surface trough situated on the coast, but no further development took place. This suggests that the baroclinic forcing was enhanced by the feedback of physical process. An increasingly unbalanced subtropical jet streak, an ageostrophic low-level jet and the associated vertical indirect circulation prior to the major development were well simulated in the Control but they were not simulated in the ?dry? experiment (without latent heating). The latent heating had a profound impact on the amplifying jet streak circulation and the vertical coupling within the system which appeared to prime the rapid cyclogenesis along the coast. The sensible beating contributed newly 18% to the surface development. It helped to build a potential temperature contrast along the coast below 900 mb. Without sensible heating, the model latent heat release was reduced. The results from the experiment without sensible and latent beating indicated that, the impact of sensible heating was partly through the moist process rather than direct beating.