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.