Improvements of the coupled WRF-Lake model over Lake Nam Co, Central Tibetan Plateau
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Improvements of the coupled WRF‑Lake model over Lake Nam Co, Central Tibetan Plateau Yang Wu1,2 · Anning Huang1,2 · Lazhu3 · Xianyu Yang4 · Bo Qiu1 · Lijuan Wen5 · Zhiqi Zhang1 · Zhipeng Fu1 · Xueyan Zhu1 · Xindan Zhang1 · Shuxin Cai1 · Yong Tang1 Received: 7 December 2019 / Accepted: 29 July 2020 © The Author(s) 2020
Abstract A series of model sensitivity simulations are carried out to calibrate and improve the Weather Research and Forecasting Model coupled with a one-dimensional lake model (WRF-Lake) based on observations over Lake Nam Co. Using the default lake model parameters, the solution of WRF-Lake exhibits significant biases in both the lake thermodynamics and regional climatology, i.e., higher lake surface temperature (LST), earlier onset of summer thermal stratification, and overestimated near-surface air temperature and precipitation induced by the lake’s excessive warming and moistening impacts. The performance of WRF-Lake is improved through adjusting the initial lake temperature profile, the temperature of maximum water density (Tdmax), the surface roughness length, and the light extinction coefficient. Results show that initializing the water temperature with spring observation mitigates the LST overestimation and reduces the timing error of the onset of thermal stratification. By further adjusting Tdmax from 4 °C to the observed value of 3.5 °C, the LST increase from June to mid-July is enhanced and the buildup of thermal stratification is more accurately predicted. Through incorporating the parameterized surface roughness length and decreasing the light extinction coefficient, the model better reproduces the observed daily evolution of LST and vertical lake temperature profile. The calibrated WRF-Lake effectively mitigates the overestimation of over-lake air temperature at 2 m height and precipitation over regions downwind the lake. This suggests that an improved lake scheme within the coupled WRF-Lake is essential for realistically simulating the lake–air interactions and the regional climate over the lake-rich Tibetan Plateau.
1 Introduction
* Anning Huang [email protected] 1
CMA‑NJU Joint Laboratory for Climate Prediction Studies, School of Atmospheric Sciences, Nanjing University, No. 163 Xianlin Avenue, Nanjing 210023, Jiangsu, China
2
Key Laboratory of Mesoscale Severe Weather/MOE and School of Atmospheric Sciences, Nanjing University, Nanjing 210023, China
3
National Tibetan Plateau Data Center, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
4
Plateau Atmosphere and Environment Key Laboratory of Sichuan Province, School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu 610225, China
5
Key Laboratory of Land Surface Process and Climate Change in Cold and Arid Regions, Chinese Academy of Sciences, Lanzhou 730000, China
The Tibetan Plateau (hereafter TP), known as the “Asian Water Tower”, harbors more than 1400 lakes with an individual surface area above 1 km2 (Ma et al. 2011; Zhang et al. 20
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