WHOI PO
Yun Chang, WHOI - Radiatively driven convection in a freshwater lake
| Date |
Time |
Location |
| December 17th, 2024 |
3:05pm-4:05pm |
Clark 507 |
Title: Radiatively driven convection in a freshwater lake
Abstract: Radiatively driven convection (RDC) in freshwater lakes occurs when water temperature is below that of maximum density (3.98 oC); as solar radiation penetrates a lake, near-surface water becomes warmer, denser, and sinks. This talk presents RDC in both onset and turbulent phases. In contrast to steady or time-period basic states in typical fluid instability problems, the basic state of the onset of RDC is time-dependent. A theory that predicts the growth rate, wavelength, and vertical structure of perturbations is derived, and is verified by direct numerical simulations. Also derived is a theory for turbulent RDC that predicts vertical velocity scale and buoyancy flux profile, which are verified by large eddy simulations. Convection cells in inertial frames grow continuously, whereas the Coriolis effect confines the growth. The duration of radiative forcing is a second factor arresting the growth. The second theory connects RDC and convection driven by surface heat flux, providing a framework to investigate the interplay with other processes such as Langmuir turbulence and submesoscale dynamics in the ocean.