The effect of jet-streak curvature on kinematic fields

Abstract

A simple two-layer primitive equation (PE) model is used to study three types of vertical motion: kinematic (PE) vertical motion, quasigeostrophic (QG) vertical motion, and vertical motion associated with an unbalanced component of the flow, partially due to inertial-gravity waves (IGW). At the initial time, a two-cell pattern of vertical motion was found for the CY and AC jet streaks as opposed to the four-cell pattern associated with the SL jet streak. Also, the vertical-motion centers for the AC and CY jet streaks were aligned more along the jet axis than across it, in contrast with the SL case. Quasigeostrophic vertical motion for the SL and CY jet cases agreed well with the PE vertical motion but were much weaker than the PE vertical motion for the AC case. The greatest mutual adjustment between the mass and momentum fields occurs with cyclonically curved jet streaks. The magnitude of the vertical motion is strongest with cyclonic jet streaks, more modest with anticyclonic jet streaks, and weakest with straight-line jet streaks. This is reflected in the maximum Rossby numbers for these cases that were 1.0, 0.40, and 0.12, respectively. -from Authors