Lei, SH; Xu, J; Li, YM; Lyu, H; Liu, G; Zheng, ZB; Xu, YF; Du, CG; Zeng, S; Wang, HJ; Dong, XZ; Cai, XL; Li, JD (2020). Temporal and spatial distribution of K-d(490) and its response to precipitation and wind in lake Hongze based on MODIS data. ECOLOGICAL INDICATORS, 108, 105684.

The diffuse attenuation coefficient K-d(lambda) is an important optical parameter that can be determined remotely. It plays a meaningful role in inland and coastal biogeochemical processes and aids in determining water quality. Four data-gathering expeditions were conducted in Lake Hongze (HZL), China, between 2015 and 2017. Based on the in situ optical and biological data, we constructed and evaluated a band ratio model for retrieving K-d (490) of HZL from MODIS/Aqua images between 2002 and 2016. Our results are as follows: (1) The developed algorithm, using the visible bands (R-rs (red)/R-rs(green)), performs robustly for K-d (490) estimation, with R-2 of 0.82 and p < 0.0001 for the modeling data. By validating with the in situ observed data, the mean absolute percentage error is determined to be 17.82%, and the root means square error is 1.52 m(-1). (2) The spatial distribution of K-d (490) strong relates with the input river that formed a cone-shaped distribution with the vertex at Huai River Estuary, decreasing from the southeast (RC) to the northern (NE) and western bays in HZL. The largest K d (490) value is in RC, with 7.10 +/- 3.03 m(-1), followed by NE and WL (wetland) with values of 6.10 +/- 2.58 m(-1) and 5.32 +/- 2.09 m(-1), respectively. (3) K-d (490) reaches high values in winter and low values in the summer although the variance is quite different in different lake areas. The seasonal distribution of K-d (490) in HZL is driven by the runoff produced by precipitation. (4) K-d (490) decreased systematically as the East Asian monsoon weakened from 2002 to 2012 that means wind has great influence on K-d (490) variation from year scale. However, human activity like sand-mining disrupted this trend, leading to the rise of K-d (490) during 2012 and 2016.