Abstract
AbstractThe Tibetan Plateau (TP) lakes are sensitive to climate change due to its seasonal ice cover, but few studies have paid attention to the freeze-thaw process of TP lakes and its key control parameters. By combining 216 simulation experiments using the LAKE2.0 model with the observations, we evaluated the effects of ice and snow albedo, ice (Kdi) and water (Kdw) extinction coefficients on the lake ice phenology, water temperature, sensible and latent heat fluxes. The reference experiment performs well in simulating the lake temperature, with a small positive bias increasing with depth, but it underestimates the ice thickness. The increase of ice albedo, snow albedo andKdiinduce a significant decrease in water temperature. Compared with the latent heat, the sensible heat flux is more sensitive to these three parameters. The ice thickness increases almost linearly with the increase of ice albedo but decreases with the increase ofKdi. The ice thickness and frozen days vary little withKdw, but increasingKdwcan decrease the water temperature. Compared with the ice albedo, theKdiand snow albedo have a large effect on the number of frozen days. This study brings to light the necessity to improve the parameterizations of the TP lakes freeze-thaw process.
Highlights
There are numerous lakes in the Tibetan Plateau (TP), with a total area of 5.0 × 104 km2 (Zhang and others, 2019)
There are no observations for the ice extinction coefficient (Kdi) in the TP lakes, but one survey shows that this value varies from 1 to 5 m−1 under snow-free conditions in the northern Europe lakes (Lei and others, 2011), which can be used for reference
From July 2011 to December 2016, the air temperature ranges from −31.9 to 19.9°C (Fig. 4a), the wind speed ranges from 0 to 20.4 m s−1, in which the wind speed exceeding 6 m s−1 accounts for 25%, and most of them occur in winter and spring (Fig. 4b)
Summary
There are numerous lakes in the Tibetan Plateau (TP), with a total area of 5.0 × 104 km (Zhang and others, 2019). The thickness of the top lake body layer is set at 0.1 m in the model This is unbefitting to lakes with transparent ice and leads to large bias under conditions of no or thin snow cover. It is necessary to carefully consider the model extinction coefficient of lake ice for TP lakes because the snow cover does not always exist and the ice is relatively transparent. The 1-D model LAKE2.0, developed by Stepanenko and others (2016) is used to quantitatively evaluate the effect of key parameters (ice albedo, snow albedo, ice extinction coefficient, and water extinction coefficient) on the lake ice phenology, the water temperature and the turbulent flux simulation in the TP lakes.
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