积雪黑碳及其对雪面反照率影响的观测和模拟研究

Observation and simulation of black carbon in snow and its effect on snow surface albedo

黑碳可以降低积雪表面反照率,进而影响气候和水文.本研究基于在长白山地区逐日积雪黑碳含量和积雪粒径等性质的观测,利用SNICAR模型分析积雪反照率的变化特征和影响因素,评估了当地积雪黑碳对反照率的削减作用.观测结果表明,2022年春季观测点积雪平均黑碳浓度为(655.2±509.3) ng·g^(-1),平均雪粒径大小为(213±70)μm,平均雪深和雪密度分别为(0.20±0.10) m和(213±41) kg·m^(-3),老雪的黑碳浓度、雪粒径和雪密度均明显高于新雪.基于观测数据模拟2022年春季积雪表面反照率,结果表明含黑碳积雪和纯雪的平均反照率分别是0.78±0.05和0.83±0.027,黑碳的存在导致平均反照率下降了0.057,在新雪和老雪分别下降了0.040和0.077.进一步模拟分析表明,随着黑碳浓度升高,积雪反照率下降速度放缓,但综合各因素后模拟的反照率下降值与黑碳浓度呈线性关系.雪粒径增大会放大黑碳的作用且这一效应随黑碳浓度上升而加强,观测期内太阳天顶角的日变化对积雪反照率的影响比季节性变化更为显著,雪密度与雪深增加也会放大黑碳的作用,但这一效应随黑碳浓度上升而减弱.本研究结果为深入探讨积雪黑碳等吸光物质的气候和水文效应提供了基础.

Black carbon can reduce the albedo of snow surface,which in turn affects climate and hydrology.In this study,based on the observations of black carbon concentration in snow,snow grain size and other snow properties at Changbai Mountain,the reduction of snow albedo from black carbon was evaluated and the characteristics and influencing factors of snow albedo was clarified by using the SNICAR model.The observation results showed that average black carbon concentration of snow was(655.2±509.3)ng·g^(-1) at the site in spring 2022,with an average snow grain size of(213±70)μm,the average snow depth and snow density(0.20±0.10)m and(213±41)kg·m^(-3),respectively.The black carbon concentration,snow grain size and snow density of aged snow were significantly higher than those of fresh snow.According to observational data,the simulation results showed that the average albedo of snow containing black carbon and pure snow were 0.78±0.05 and 0.83±0.027 in spring of 2022,and an average reduction of 0.057 with the presence of black carbon in snow was quantified,with reductions of 0.040 and 0.077 in fresh and aged snow,respectively.Further simulations showed that the rate of snow albedo decrease slowed as the increasing of black carbon concentration,and yet the reduction of albedo showed a linear relationship with black carbon concentration when combining all factors.Increasing snow grain size amplified the effect of black carbon on albedo,which strengthened with raising of black carbon concentration.The diurnal variation of solar zenith angle during the observation period had much more significant effect on snow albedo than seasonal variation.Enhancement snow density and snow depth also amplified the effects of black carbon on snow albedo,which weakened with increasing black carbon concentration.