Heat Transport and Local Temperature Measurements of Geostrophic Rotating Thermal Convection

Rotating Rayleigh-Benard convection is an idealized model of geophysical convective motions where buoyancy and rotation compete. The parameters governing such flows are the Rayleigh number $Ra$ proportional to $\Delta T$ across the cell height $h$, the Taylor number $Ta$ proportional to $\Omega^2$ where $\Omega$ is the angular rotation rate, and the Prandtl number $Pr$. In the turbulent state, experiments have demonstrated that normalized heat transport $Nu$ for the rotating state at small $Ro = \sqrt{Ra/(Pr Ta)}$ scales in the same manner as the non-rotating heat transport with a small enhancement of heat transport that depends on $Ra$ and $Pr$. We explore global heat transport and local temperature measured at multiple vertical positions along the cell center line of a square convection cell with aspect ratio $\Gamma=L/h\approx 4$ where $L$ is a lateral side and $h=12.1$ cm is the cell height. We focus on the Ra range $5 \times 10^6 < Ra < 5 \times 10^8$ for $5 \times 10^8 < Ta < 5 \times 10^{10}$ from onset up to the crossover to turbulent scaling where $Nu \sim Ra^{0.29}$. We report on the scaling of $Nu$ with $Ra$ at constant $Ta$ in that range and infer local convective structure from vertical spatial correlation of temperature fluctuations.