Characteristics of over-water surface stress during strex

Surface stress values obtained from the NOAA Ship OCEANOGRAPHER during STREX indicate that wind speed and stability dependent bulk derived stress values are two to three times too low in surface pre-frontal, pre-trough and pre-ridge regions of transiting synoptic systems. The measured stress values were based on calculations of turbulent kinetic energy dissipation rates using hot film measured velocity variances. Bulk stress values obtained with wind speed (neutral drag coefficient) and stability dependencies in the Large and Pond derivation agreed very well with the measured values in other regions of the synoptic systems. In situ wave information was not adequate to relate differences to coupled vector wind and wave fields. However, analyses and interpretation of wind and stability effects suggest that wind wave interaction was the reason for the observed sub-synoptic (mesoscale) stress enhancements.