G. Balasubramanian et Mk. Yau, EXPLOSIVE MARINE CYCLOGENESIS IN A 3-LAYER MODEL WITH A REPRESENTATION OF SLANTWISE CONVECTION - A SENSITIVITY STUDY, Journal of the atmospheric sciences, 52(5), 1995, pp. 533-550
A three-layer primitive equation model with a representation of slantw
ise convection is used to study explosive marine cyclogenesis. A simpl
e representation of boundary layer and shallow and deep cloud types is
considered. Apart from the control simulation, experiments are conduc
ted to test the sensitivity of the bent-back warm front and the explos
ive deepening to various model parameters. The major results are as fo
llows: 1) The control simulation produces a realistic explosive cyclon
e. 2) The cloud mass fraction at the top of the boundary layer, which
is equal to the fractional area of slantwise ascent in a grid box, ess
entially determines the cloud mass flux transported into the large-sca
le atmosphere. The thermal gradient in the bent-back warm frontal regi
on and the final deepening strongly depend on this parameter. 3) Shall
ow clouds are relatively insignificant in affecting the dynamics of ex
plosive cyclones. 4) The surface drag force weakens the development of
strong horizontal wind shear and the bent-back warm front. 5) The the
rmal gradient in the bent-back warm front gradually increases with the
thermodynamic disequilibrium between the sea surface and the atmosphe
ric boundary layer. 6) Enhanced vertical wind shear increases the deep
ening rate. However, the asymmetry in the wave development and strong
pressure falls near the warm front are associated with slantwise conve
ction. 7) Weak low-level stability has significant impact on cyclogene
sis. 8) The effect of stable condensation is to moderately accelerate
the development of the baroclinic wave.