Winter Circulations and Wavenumber Domain Energetics at 200MB1

Abstract

Some of the characteristic features of the winter monsoon circulations are investigated using 200mb wind data operationally determined by the National Meteorological Center, Washington, D.C., during three winters in 1970-71, 1971-72, and 1972-73. Three-year winter mean 200mb divergence was large over the East China Sea, the Philippines, the South China Sea, and Indonesia. A pronounced velocity potential outflow center was located near Indonesia with a prominent N-S overturning, vertical circulation along 125°E, while a distinct 200mb anticyclone lay centered to the east of the Philippines.
Energy equations, similar to that proposed by Saltzman, were applied to three specific latitudinal regions to investigate the atmospheric energetics in the wavenumber domain during the three winters; region 1 (14.8°N-30.8°N), region 2 (0°-14.8°N), and region 3 (14.8°S-0°). In region 1, wave-zonal mean flow interactions are substantially more pronounced than wave-wave nonlinear interactions. Regions 2 and 3 are characterized by the predominance of wave-wave interaction processes.
A computational model to partition kinetic energy exchanges into standing (winter mean) and transient wave motions, has been proposed. Most transient waves, over all regions, receive kinetic energy from standing waves via “standing to transient” wave interactions. All transient waves furnish kinetic energy to zonally averaged winter mean flows with large contributions from wavenumbers 3 to 8.