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Airmass transformation over the South China Sea during a winter MONEX cold surge
Author(s) -
Martin David W.,
Reiff J.,
Mower R. N.
Publication year - 1988
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49711447905
Subject(s) - surge , entrainment (biomusicology) , subsidence , climatology , environmental science , submarine pipeline , boundary layer , meteorology , atmospheric sciences , geology , oceanography , geography , mechanics , paleontology , philosophy , physics , structural basin , rhythm , aesthetics
Several studies have linked a wintertime cycle of deep, moist near‐equatorial convection to surges of cold air from Asia. According to an early hypothesis two successive streams of surge air reach north Borneo and offshore waters of the South China Sea. The first, which follows a long over‐water trajectory, is warm by the time it arrives off Borneo. The second, which follows a short over‐water trajectory, still is cool when it arrives off Borneo. More recent hypotheses suggest only the second stage of the surge involves an airstream from Asia and drying rather than cooling is the predominant downstream thermodynamic effect on this airstream. By means of trajectory calculations and an airmass transformation (AMT) model we test these ideas for a moderate cold surge from December 1978. In particular, we contrast the roles, in the transformation process, of surface fluxes of latent and sensible heat and of boundary layer entrainment. At no time through the course of the surge did we find boundary layer trajectories of the second (short path) type. Nevertheless, late in the course of the case study surge dry air did appear at the surface off the south‐east coast of Vietnam. Neither sea surface temperature nor initial airmass structure could account for the local nature of the drying. The explanation most consistent both with observations and AMT model results is entrainment of air that had been dried by local subsidence at and above the top of the marine boundary layer.