积雪和沙尘对冰封期青海湖辐射和温度的影响

Effects of Snow and Dust on Radiation and Temperature in Qinghai Lake during Ice-covered Period

青藏高原广泛而密集地分布着大量湖泊,受高海拔影响,湖泊多季节性冻结且冰封期较长。湖冰可显著改变湖面和水下辐射、能量传输过程,进而影响局地、区域气候及冰下水生生态系统;然而目前对高原湖泊冰封期湖面特征及湖下热力过程的认识尚不明确。因此,本研究于2022年2月6-28日在青藏高原最大湖泊青海湖进行了冰封期多层湖水-湖冰-大气的系统野外观测;利用获取的野外观测数据及视频影像,结合台站降水资料,研究了冰封期青海湖不同冰面覆盖条件对湖水-湖冰-大气辐射和温度的影响。结果表明,降雪、沙尘、大风等不同天气过程可显著改变冰面物质的分布情况,导致青海湖冰面覆盖物和冰层的厚度发生变化。冰面覆盖物的反照率差异及其对太阳辐射的吸收差异使入射到湖表覆盖物上界面、湖冰上界面的短波辐射和湖冰温度日变化存在显著差别。裸冰时反照率较小且上层少有可吸收太阳辐射的覆盖物,冰面温度的日变化较大。积雪的高反射特性和沙尘的强吸收特性均削弱了入射湖冰表面的短波辐射,使得湖冰温度日变化较小。

Many lakes are widely and densely distributed on the Qinghai-Tibet Plateau.Due to the high altitude,the lakes seasonally freeze with a long ice-covered period.Lake ice can significantly affect the local and regional climate and the sub-glacial aquatic ecosystem by changing the transfer process of radiation energy on and in the lakes.However,their characteristics during the ice-covered period still remain unclear.Therefore,from February 6 to 28,2022,we conducted a systematic observation of water ice air in Qinghai Lake,the largest lake on the Qinghai-Tibet Plateau.Using field observation data,video images and the precipitation data of peripheral observation stations,the influence of different ice cover conditions on the radiation and temperature of the waterice-atmosphere on Qinghai Lake during the ice-covered period was analyzed.Results showed that different weather processes such as snowfall,sand and gale could remarkably change the property of cover on the ice,leading to variations of ice thickness on Qinghai Lake.Furthermore,the discrepancies of solar radiation absorption and reflection of different covers result in energy equilibrium that directly dictate ice surface temperature at water-iceatmosphere interface.Bare ice with low albedo and low absorption induced the relatively strong net solar radiation and the correspondingly large diurnal variations of ice temperature.Compared to bare ice,the high reflection of snow cover and the strong absorption of sand and dust make the ability of net short-wave radiation to penetrate ice weaker,and the diurnal variation of lake ice temperature is smaller.