水冰雪反照率参数化通用模型

A parameterized general model of water, ice and snow albedo

对于气候寒冷、降雪频繁的冰封河湖,冰盖和雪盖的反照率对气候和冰厚变化有很大影响。应用Fresnel理论得出纯水和纯水冰可用相同反照率公式计算的结论。基于现有的原型观测资料,提出了水冰反照率参数化通用模型。在此基础上,借鉴CCSM3雪冰日平均反照率参数化模型,提出了水冰雪反照率参数化通用模型。该模型考虑了纬度及地球自转和环绕太阳运行的规律,具有很好的普适性。计算分析表明,纬度和日期对水冰雪日平均反照率有很大影响,反照率大小随日期或月份变化,纬度越高,反照率越大。与冰厚对反照率的影响相比,太阳高度角随纬度和日期变化产生的影响大得多。水冰雪反照率参数化通用模型计算结果与原型观测结果的对比证明,两者吻合较好,而现有常用以冰厚为依据的反照率模型计算结果远远偏离观测结果。

For frozen rivers and lakes with cold climate and frequent snowfall, the albedo of ice cover and snow cover has great influence on climate and ice thickness change. Using Fresnel theory, it is concluded that pure water and pure water ice can be calculated by the same albedo formula. Then, based on the existing prototype observation data, a general parameterization model of water-ice albedo is proposed. On this basis, referring to the parameterization model of CCSM3 snow-ice daily average albedo, a general parameterization model of water-ice-snow albedo is proposed,considering the latitude, the earth’s rotation and the variation laws around the sun, thus making the model very universal. Calculation and analysis show that latitude and date have great influence on the daily average albedo of water, ice and snow, and the albedo varies with the date or month. The higher the latitude, the greater the albedo.Compared with the influence of ice thickness on albedo, the influence of solar altitude angle on latitude and date changes is much greater. The comparison between the calculation results of the general parameterization model of water-ice-snow albedo and the prototype observation results proves that the two are in good agreement, while the calculation results of the existing commonly used albedo model based on ice thickness are far from the observation results.