Evolution dynamics of tropical ocean-atmosphere annual cycle variability

Journal Article · Sun Dec 01 04:00:00 EST 1996 · Journal of Climate

DOI:https://doi.org/10.1175/1520-0442(1996)009<3187:EDOTOA>2.0.CO;2· OSTI ID:447205

Nigam, S ^[1]; Chao, Y ^[2]

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1. Univ. of Maryland, College Park, MD (United States)
2. California Institute of Techology, Pasadena, CA (United States)

The structure of ocean-atmosphere annual cycle variability is extracted from the revised Comprehensive Ocean-Atmosphere Data Set SSTs, surface winds, and the latent heat (LH) and net shortwave (SW) surface fluxes using the covariance-based rotated principal component analysis method. The coupled annual cycle variability is concisely described using two modes that are in temporal quadrature. The first, peaking in June/July (and December/January), represents monsoonal flow onto Indochina, Central America, and western Africa. The second mode peaks in September/October and March/April when it represents the extreme phases of the SST annual cycle in the eastern oceans. Analysis of the surface momentum balance in the Pacific cold tongue core shows the equatorial flow, and in particular the zonal wind, to be dynamically consistent with the SST gradient during both the cold tongue`s nascent (June/July) and mature (September/October) phases; the dynamical consistency improves when the impact of nearsurface static stability variation on horizontal momentum dissipation is also considered. Evolution structure of the extracted annual cycle, moreover, shows the easterly wind tendency to lead SST cooling in the off-coastal zone. Taken together, these findings suggest that the Pacific cold tongue westward expansion results from local interaction of the zonal wind and zonal SST gradient, as encapsulated in the proposed {open_quotes}westward expansion hypothesis{close_quotes} - a simple analytic model of which is also presented. 29 refs., 10 figs.

• OSTI ID: 447205
• Journal Information: Journal of Climate, Journal Name: Journal of Climate Journal Issue: 12 Vol. 9; ISSN 0894-8755; ISSN JLCLEL
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
AIR-WATER INTERACTIONS
ANNUAL VARIATIONS
CLIMATES
COOLING
EQUATOR
PACIFIC OCEAN
WIND