Philippines monsoon dynamics

Philippines Big

A northerly monsoon surge on 1 January 2005 generated intense wind jets and wakes whose associated wind stress curl pattern (left) induced a pair of counter-rotating oceanic eddies (right) to propagate away from the islands into the South China Sea.

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Two winter monsoon surge events (northerly and easterly) of January 2005 are captured in a one-way coupled atmosphere (8 km resolution) and ocean (3 km resolution) simulation of the Philippines region.  Intensified wind jets and wakes in the lee of Mindoro and Luzon Islands induce the generation and migration of a pair of counter-rotating oceanic eddies in the model, with propagation direction related to the orientation of the winds during each of the surges.  Features shared by the eddies include size (100-200 km), depth (~300 m) and propagation speed (0.1 - 0.15 m s-1 for cyclones).  Mean wintertime model wind stress positive (negative) curl coincides with the climatological cyclone (anticyclone) distribution from a prior 8-year altimetry-based census of eddies in the southeast quadrant of the South China Sea during the winter monsoon.  Moreover, the simulation results agree with contemporaneous satellite and historical in situ data characterizing regional oceanic eddy and atmospheric surface jet properties.

Subsequent two-way coupled runs at higher resolution for winter 2008 reinforce these results and are verified using in situ shipboard underway data from a PhilEx research cruise.

Pullen, J., J. D. Doyle, P. May, C. Chavanne, P. Flament and R. Arnone, "Monsoon surges trigger oceanic eddy formation and propagation in the lee of the Philippine Islands," Geophysical Research Letters, 35, L07604, doi:10.1029/2007GL033109, 2008 (pdf)

Rypina, I., L. Pratt, J. Pullen, J. Levin and A. Gordon, “Chaotic advection in an archipelago,” Journal of Physical Oceanography, 40(9), 1988-2006, 2010 (pdf).

May, P. W., J. D. Doyle, J. Pullen, and L. David, “Two-way coupled atmosphere-ocean modeling of the PhilEx intensive observational period,” Oceanography, 24(1), 48-57, 2011 (pdf).

Pullen, J., A. L. Gordon, J. Sprintall, C. M. Lee, M. A. Alford, J. D. Doyle, P. W. May, “Atmospheric and oceanic processes in the vicinity of an island strait,”Oceanography, 24(1), 112-121, 2011 (pdf).