Final technical report of Grant ATM 83-15175 "tropical and monsoonal studies"

Alternate Titles

• NPS-63-88-001.

Description

This project studies a variety pf large-scale motions in the tropics and subtropics particularly those associated with the Asian monsoon circulations. It consists of four parts -- (1) theoretical studies of planetary scale motion forced by tropical heating: The effects of vertical shear, vertical differential damping and planetary boundary layer were found to influence the forcing of midlatitude motions by tropical heat sources. In addition, the vertical interaction of simple modes may be responsible for the maintenance of the eastward propagating 30-50 day oscillations; (2) Observational studies of planetary scale motions: The day-to-day variation of the East Asian Jet was found to correlate positively with that of the tropical divergent flow south of it, suggesting the importance of tropical forcing through the local Hadley cell. The transient forcing of time-mean planetary scale circulation was also studied using a nine-year data set; (3) Theoretical studies of zonal asymmetry: Several differences between parallel flow and non-parallel flow instabilities in terms of spatial and time growth rates were found using the two-scale technique; (4) Studies of the Mei-Yu system of the East Asian summer monsoon: A numerical experiment suggested that the Low-Level Jet Associated with Mei-Yu fronts receives energy through an equatorward, convection-driven secondary circulation which is quite different from the cross-frontal circulation associated with dry fronts.

Subjects