Observations and model simulations of snow albedo reduction in seasonal snow due to insoluble light-absorbing particles during 2014 Chinese survey

Abstract

Abstract. A snow survey was carried out to collect 13 surface snow samples (10 for fresh snow, and 3 for aged snow) and 79 subsurface snow samples in seasonal snow at 13 sites across northeastern China in January 2014. A spectrophotometer combined with chemical analysis was used to quantify snow particulate absorption by insoluble light-absorbing particles (ILAPs, e.g., black carbon, BC; mineral dust, MD; and organic carbon, OC) in snow. Snow albedo was measured using a field spectroradiometer. A new radiative transfer model (Spectral Albedo Model for Dirty Snow, or SAMDS) was then developed to simulate the spectral albedo of snow based on the asymptotic radiative transfer theory. A comparison between SAMDS and an existing model -the Snow, Ice, and Aerosol Radiation (SNICAR) -indicates good agreements in the model-simulated spectral albedos of pure snow. However, the SNICAR model values tended to be slightly lower than those of SAMDS when BC and MD were considered. Given the measured BC, MD, and OC mixing ratios of 100-5000, 2000-6000, and 1000-30 000 ng g −1 , respectively, in surface snow across northeastern China, the SAMDS model produced a snow albedo in the range of 0.95-0.75 for fresh snow at 550 nm, with a snow grain optical effective radius (R eff ) of 100 µm. The snow albedo reduction due to spherical snow grains assumed to be aged snow is larger than fresh snow such as fractal snow grains and hexagonal plate or column snow grains associated with the increased BC in snow. For typical BC mixing ratios of 100 ng g −1 in remote areas and 3000 ng g −1 in heavy industrial areas across northern China, the snow albedo for internal mixing of BC and snow is lower by 0.005 and 0.036 than that of external mixing for hexagonal plate or column snow grains with R eff of 100 µm. These results also show that the simulated snow albedos by both SAMDS and SNICAR agree well with the observed values at low ILAP mixing ratios but tend to be higher than surface observations at high ILAP mixing ratios.

Concentrations and source regions of light-absorbing particles in snow/ice in northern Pakistan and their impact on snow albedo

“…A wide range of values has been reported by different authors for BC concentrations in snow and ice samples from different regions (Table S2). The concentrations of BC in our samples were higher than those reported by many authors (Table S2) but were comparable with the results reported by Xu et al (2012) in the Tien Shan, by Li et al (2016) in the northeast of the Tibetan Plateau, by Wang et al (2017) in northern China, and by Zhang et al (2017) in western Tien Shan, central Asia. High concentrations indicate high deposition rates on the snow and ice surface, but there are several possible reasons for a wide variation in values apart from differences in deposition rates, including differences in sampling protocols, geographical/sampling location and elevation of sampling site (Qu et al, 2014), and year/season of sampling.…”

Impact of Grain Shape and Multiple Black Carbon Internal Mixing on Snow Albedo: Parameterization and Radiative Effect Analysis

“…The grain nonsphericity effect can be even larger if considering the same snow volume/mass (equivalently R v ) rather than effective size (R e ) (see section 3.4). Wang et al (2017) found that the spectrally (0.4-1.4 μm) averaged albedos of spherical snow grains are lower than those of hexagonal plates and fractal grains by 0.008 and 0.017, respectively, based on the AART theory (Kokhanovsky & Zege, 2004). Dang et al (2016) (5) and (6) Observations (e.g., Dominé et al, 2003, Erbe et al, 2003 suggest that Koch snowflakes and spheroids could be used to mimic fresh and aged snow, respectively.…”

Distributions and light absorption property of water soluble organic carbon in a typical temperate glacier, southeastern Tibetan Plateau

“…While the mean OC concentration in surface aged snow and granular ice was 2090 ± 568 ng g À1 and 4304 ± 358 ng g À1 , respectively. BC and OC deposited on the snow and glaciers were widely considered as insoluble light-absorbing impurities (ILAIs) (Wang et al, 2017;Niu et al, 2018). ILAIs combined with WSOC in snow and glacier can be defined as lightabsorbing matter (LAM), which considerably reduces snow spectral albedo, absorbs large amount of solar energy, and accelerates the retreat of glaciers.…”