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

摘要

A global constant value of the extinction coefficient (iK/isubd/sub) 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 iK/isubd/sub for Lake Erie. The CoastColour algorithm was applied to MERIS satellite imagery to estimate iK/isubd/sub. The constant (0.2?msup?1/sup) and satellite-derived iK/isubd/sub 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 iK/isubd/sub value (0.2?msup?1/sup). No significant improvement was found in FLake-simulated lake surface water temperature (LSWT) when iK/isubd/sub variations in time were considered using a monthly average. Therefore, results suggest that a time-independent, lake-specific, and constant satellite-derived iK/isubd/sub value can reproduce LSWT with sufficient accuracy for the Lake Erie station. brbrA sensitivity analysis was also performed to assess the impact of various iK/isubd/sub values on the simulation outputs. Results show that FLake is sensitive to variations in iK/isubd/sub 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 iK/isubd/sub variations was more pronounced in the simulation of MWCT, LBWT, and MLD. The model was particularly sensitive to iK/isubd/sub values below 0.5?msup?1/sup. This is the first study to assess the value of integrating iK/isubd/sub from the satellite-based CoastColour algorithm into the FLake model. Satellite-derived iK/isubd/sub 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 iK/isubd/sub is not commonly measured./p