TY - JOUR
T1 - The response of quasigeostrophic oceanic vortices to tropical cyclone forcing
AU - Jaimes, Benjamin
AU - Shay, Lynn K.
AU - Halliwell, George R.
PY - 2011
Y1 - 2011
N2 - The response of quasigeostrophic (QG) oceanic vortices to tropical cyclone (TC) forcing is investigated using an isopycnic ocean model. Idealized oceanic currents and wind fields derived from observational data acquired during Hurricane Katrina are used to initialize this model. It is found that the upwelling response is a function of the curl of wind-driven acceleration of oceanic mixed layer (OML) currents rather than a function of the wind stress curl. Upwelling (downwelling) regimes prevail under the TC's eye as it translates over cyclonic (anticyclonic) QG vortices. OML cooling of ~1°C occurs over anticyclones because of the combined effects of downwelling, instantaneous turbulent entrainment over the deep warm water column (weak stratification), and vertical dispersion of near-inertial energy. By contrast, OML cooling of ~4°C occurs over cyclones due to the combined effects of upwelling, instantaneous turbulent entrainment over regions of tight vertical thermal gradients (strong stratification), and trapping of near-inertial energy that enhances vertical shear and mixing at the OML base. The rotational rate of the QG vortex affects the dispersion of near-inertial waves. As rotation is increased in both cyclones and anticyclones, the near-inertial response is shifted toward more energetic frequencies that enhance vertical shear and mixing. TCinduced temperature anomalies in QG vortices propagate westward with time, deforming the cold wake. Therefore, to accurately simulate the impact of TC-inducedOMLcooling and feedback mechanisms on storm intensity, coupled ocean-atmosphere TC models must resolve geostrophic ocean eddy location as well as thermal, density, and velocity structures.
AB - The response of quasigeostrophic (QG) oceanic vortices to tropical cyclone (TC) forcing is investigated using an isopycnic ocean model. Idealized oceanic currents and wind fields derived from observational data acquired during Hurricane Katrina are used to initialize this model. It is found that the upwelling response is a function of the curl of wind-driven acceleration of oceanic mixed layer (OML) currents rather than a function of the wind stress curl. Upwelling (downwelling) regimes prevail under the TC's eye as it translates over cyclonic (anticyclonic) QG vortices. OML cooling of ~1°C occurs over anticyclones because of the combined effects of downwelling, instantaneous turbulent entrainment over the deep warm water column (weak stratification), and vertical dispersion of near-inertial energy. By contrast, OML cooling of ~4°C occurs over cyclones due to the combined effects of upwelling, instantaneous turbulent entrainment over regions of tight vertical thermal gradients (strong stratification), and trapping of near-inertial energy that enhances vertical shear and mixing at the OML base. The rotational rate of the QG vortex affects the dispersion of near-inertial waves. As rotation is increased in both cyclones and anticyclones, the near-inertial response is shifted toward more energetic frequencies that enhance vertical shear and mixing. TCinduced temperature anomalies in QG vortices propagate westward with time, deforming the cold wake. Therefore, to accurately simulate the impact of TC-inducedOMLcooling and feedback mechanisms on storm intensity, coupled ocean-atmosphere TC models must resolve geostrophic ocean eddy location as well as thermal, density, and velocity structures.
KW - Internal waves
KW - Numerical analysis/modeling
KW - Oceanic mixed layer
KW - Tropical cyclones
KW - Upwelling/downwelling
KW - Vortices
UR - http://www.scopus.com/inward/record.url?scp=82055186326&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=82055186326&partnerID=8YFLogxK
U2 - 10.1175/JPO-D-11-06.1
DO - 10.1175/JPO-D-11-06.1
M3 - Article
AN - SCOPUS:82055186326
VL - 41
SP - 1965
EP - 1985
JO - Journal of Physical Oceanography
JF - Journal of Physical Oceanography
SN - 0022-3670
IS - 10
ER -