| Oceanic subseasonal variability forced by orographic wind jets is investigated in the east Pacific warm pool and the South China Sea. Orographic wind jets and their strong wind stress curls trigger strong upper ocean responses, including upwelling, wind-evaporation cooling, and entrainment. Entrainment and evaporative cooling due to high wind speed result in local sea surface temperature (SST) minima underneath the wind jets. The strong wind stress curls drive ocean currents and excite propagating signals in thermocline depth and sea surface height (SSH).;In the east Pacific warm pool, strong orographic wind jets, gap winds, are mainly associated with southward penetration of midlatitude frontal systems in winter. High-frequency gap winds force pronounced subseasonal variability in SSH that is organized into eddy trains along high variance bands stretching southwestward from the Gaps of Tehuantepec and Papagayo. Initially forced by Ekman pumping near the coast, subseasonal eddies are amplified along the propagation path by dynamical instabilities of the background flow and by subsequent intensifications of the wind jets. The results from an eddy-resolving, ocean general circulation model forced by a QuikSCAT satellite wind product support the wind-forced mechanism.;In the South China Sea (SCS) the orographic wind jet takes place in summer when the southwest monsoon impinges on the Annam Cordillera. Following an intraseasonal intensification of the wind jet (>12 m/s), a cold SST filament advected by the offshore inter-gyre boundary current (within 1 week), and the double ocean gyre circulation strengthens upon the arrival of wind-forced Rossby waves from mid basin (2-3 weeks later). Surface wind speed decreases by 2-3 m/s over the cold filament in response to an increased in surface atmospheric stability. The SCS summer intraseasonal wind jet events are part of the planetary-scale summer intraseasonal oscillation.;The thesis research takes advantage of high spatio-temporal resolution of recent satellite observations, and shows that independent observations of surface winds and SSH are mutually consistent within the context of wind-forced ocean adjustments. Orographic wind jets are an important source of subseasonal variability in SSH, a result of important implications for physical, biochemical, and fisheries oceanography. |
