基于能量平衡的分析模型在青海湖湖冰模拟中的应用

Application of the Analytic Model Based on Energy Balance into the Lake Ice Simulation of Qinghai Lake

湖冰对气候变化响应敏感,在全球变暖的背景下,湖冰总体呈现衰退趋势,甚至北半球部分湖泊未来有可能不再冻结。青藏高原湖泊分布广泛,但目前对于湖冰的模拟研究开展较少,对青藏高原湖冰特征及冻结系数的认识还较为有限。本文利用飞航式雷达湖冰测厚数据、青海湖气象观测数据、ERA5-Land再分析数据、MODIS地表温度数据以及Aqua/MODIS卫星遥感图像,通过度日法湖冰生长模型确定了青海湖冻结系数A_(0),研究结果显示A_(0)在青海湖具有空间异质性和时间异质性,且前者比后者更为明显。进一步利用度日法和基于能量平衡的分析模型模拟了青海湖的湖冰演变,结果表明:相较于度日法,基于能量平衡的分析模型模拟的青海湖2018-2019年冰期的开始结冰时间、融化结束时间与湖冰厚度同实际观测更为符合。分析模型是一种优于度日法、适用于青海湖湖冰模拟研究的方法,该方法能够综合考虑辐射、能量交换、气象要素、湖泊深度等因素的影响,其物理过程更为完善,同时也弥补了度日法模拟精度依赖于冻结初日的确定且无法表现融化过程的缺陷。

Lake ice is sensitive to climate change.Under the background of global warming,lake ice is generally declining,and even some lakes in the Northern Hemisphere may not freeze in the future.Lakes are widely distributed in the Qinghai-Xizang Plateau,but there are few studies on lake ice simulation.In addition,the understanding of lake ice characteristics and its freezing coefficients on the Qinghai-Xizang Plateau is still relatively limited.The freezing coefficient A_(0)of Qinghai Lake was calculated by the degree-day approach for ice growth,using the lake ice thickness measurement data from fly-by-wire radar,meteorological observation data of Qinghai Lake,ERA5-Land reanalysis data,MODIS land surface temperature data and Aqua/MODIS satellite remote sensing images.The results show that A_(0)has spatial and temporal heterogeneity in Qinghai Lake,and the former is more obvious than the latter.Both the degree-day approach and the energy balance-based analytical model are applied to simulate the lake ice evolution of Qinghai Lake on the Qinghai-Xizang Plateau.The results show that,compared with the degree-day method,the simulations of the start of ice formation,the end of melting and the thickness of lake ice for the 2018-2019 ice season of Qinghai Lake by the energy balance-based analytic Model are more consistent with the observations.The analytical model is a better method than the degree-day method for simulating the ice of Qinghai Lake.It incorporates the effects of radiation,energy exchange,meteorological elements,lake depth and other factors,thus improving the physical processes and compensating for the fact that the accuracy of the degree-day method of simulation depends on the first date of freezing and cannot simulate the melting process.