2.5 Energy Balance Ratio
The energy balance ratio (Feng et al., 2016) allows us to quantify the energy balance closure and therefore to correct underestimated turbulent heat fluxes (see Sect. 3.3). It is defined as follows:
\(\text{EBR}=\frac{H+\text{LE}}{R_{n}-{H}_{S}}\ \times 100\)(3)
where Rn is the net radiation and ΔHS is the heat storage variation along the water column, defined as
\({H}_{S}=\ \int_{0}^{h}{\rho_{w}\ c_{\text{pw}}\ \frac{\overset{\overline{}}{{T}_{w}}}{t}\ \text{dh}}\)(4)
where ρw is the water density (kg m−3), cpw is the specific heat of water (J kg−1 K−1), ΔTw is the water temperature difference between two time steps (K), Δt is the time period (30 min), and his the water layer thickness (m). To determine the EBR, ΔHS was calculated over the entire depth of the epilimnion, which is the distance between the surface (0 m) and the position of the thermocline (h ). Note that the epilimnion thickness varies over the year. On average, h = 15 m from June to October, h = 30 m from November to December, and h = 0 m from January to May.