Favorable environments for explosive cyclogenesis in a modified two-layer Eady model

Abstract

A modified two-layer Eady model is used to find favorable environments for explosive cyclogenesis by examining baroclinic instability of both short and long waves. The model includes Ekman dissipation and low-level sensible heating, and allows both static stabilities and vertical shears to be different bui constant in each layer. It is found that an enhanced lowlevel shear, a reduced low-level static stability, a relatively large upper-level static stability, and an appropriate height of the interface are favorable for the short-wave development, and that an enhanced upper-level shear and a relatively small upper-level static stability are favorable for the long-wave development, while having opposite effects on the short wave. A small Ekman dissipation is favorable for the development of both waves. Newtonian sensible heating does not directly enhance the development of both waves. A favorable environment for explosive cyclogenesis may not be expressed by a single parameter, but rather by a combination of baroclinic instability with several parameters which contribute collectively to the development of both short and long waves. The relative phase of these waves also plays an important part: the development is enhanced when the surface cyclone is ahead of the upper level wave trough by in.

Interpretation of discrete and continuum modes in a two-layer Eady model

“…Prior to Müller (1991), Blumen (1979) and Weng and Barcilon (1987) had already investigated two-layer Eady models which are bounded from above by a second rigid lid. Those models sustain short-wave unstable modes.…”

Συμβολη Στη Μελετη Του Προβληματος Της Κυκλογενεσης Στο Αιγαιο Πελαγος

“…Η διαδικασία αυτή χαρακτηρίζεται από υψηλές τιμές του δυναμικού στροβιλισμού στην ανώτερη τροπόσφαιρα. Οι Uccellini et al (1985) υποστήριξαν ότι η αναδίπλωση πρέπει να είναι ευνοϊκός παράγοντας πριν την κυκλογένεση, συμφωνώντας με τους Bosart and Lin (1984) και Weng and Barcilon (1987). Ωστόσο, το συμπέρασμα αυτό διαφέρει από εκείνο των Boyle and Bosart (1983), που τόνισαν την ταυτόχρονη εισβολή του στρατοσφαιρικού αέρα και της κυκλογένεσης στην επιφάνεια.…”