Satellite-derived light extinction coefficient and its impact on thermal structure simulations in a 1-D lake model

Abstract

Abstract.A global constant value of the extinction coefficient (K d ) is usually specified in lake models to parameterize water clarity. This study aimed to improve the performance of the 1-D freshwater lake (FLake) model using satellite-derived K d for Lake Erie. The CoastColour algorithm was applied to MERIS satellite imagery to estimate K d . The constant (0.2 m −1 ) and satellite-derived K d values as well as radiation fluxes and meteorological station observations were then used to run FLake for a meteorological station on Lake Erie. Results improved compared to using the constant K d value (0.2 m −1 ). No significant improvement was found in FLake-simulated lake surface water temperature (LSWT) when K d variations in time were considered using a monthly average. Therefore, results suggest that a timeindependent, lake-specific, and constant satellite-derived K d value can reproduce LSWT with sufficient accuracy for the Lake Erie station.A sensitivity analysis was also performed to assess the impact of various K d values on the simulation outputs. Results show that FLake is sensitive to variations in K d to estimate the thermal structure of Lake Erie. Dark waters result in warmer spring and colder fall temperatures compared to clear waters. Dark waters always produce colder mean water column temperature (MWCT) and lake bottom water temperature (LBWT), shallower mixed layer depth (MLD), longer ice cover duration, and thicker ice. The sensitivity of FLake to K d variations was more pronounced in the simulation of MWCT, LBWT, and MLD. The model was particularly sensitive to K d values below 0.5 m −1 . This is the first study to assess the value of integrating K d from the satellite-based CoastColour algorithm into the FLake model. Satellite-derived K d is found to be a useful input parameter for simulations with FLake and possibly other lake models, and it has potential for applicability to other lakes where K d is not commonly measured.

Effects of the Largest Lake of the Tibetan Plateau on the Regional Climate

“…The water in Qinghai Lake is clear because of its oligotrophic state. Hence, the default WRF‐FLake value of the extinction coefficient ( K d ) of 3 m −1 (corresponding to ~0.5‐m Secchi disk depth [SDD] according to Arst et al, 2008; Zolfaghari et al, 2017) was found too large for Qinghai Lake. The study of Huang et al (2019) proved that setting the light extinction coefficient to 0.1 m −1 instead of 3 m −1 can greatly improve the FLake performance at Nam Co Lake.…”

Simulation of the Surface Energy Flux and Thermal Stratification of Lake Taihu with Three 1-D Models

“…The extinction coefficient significantly affects water temperature when the water is clear, though it almost has no effect when the water is turbid [22]. The usage of satellite data to determine the lake extinction coefficient can effectively enhance the simulation accuracy [23]. The evaluation of seven lake models to Africa's great lakes showed that the models that account for the effects of salinity and dissolved gasses on water column stratification can accurately represent the meromictic state of Lake Kivu [18].…”

Validation and Sensitivity Analysis of a 1‐D Lake Model Across Global Lakes

“…Furthermore, the light extinction coefficient has also been found to have distinct effects on the thermocline depth and thus the vertical thermal structure (Heiskanen et al, 2015;Zolfaghari et al, 2017). Shatwell et al (2016) found that lakes with moderate depths and relatively high light extinction can switch between polymictic and dimictic states and thus experience seasonal shifts in water transparency and mixing regime due to fluctuations of phytoplankton biomass.…”