Black carbon mass loadings in snow quantified with a Single Particle Soot Photometer (SP2) and a Integrating Sandwich Spectrophotometer (ISSW)

Correctly attributing light absorption in snow to its proper source is important for assessing the relative impact of absorbing constituents on snow and ice melt and its associated positive climate feedback. Here we evaluate the ability of a Single Particle Soot Photometer (SP2) to quantify black carbon (BC) concentrations in melted snow. We compare SP2 measurements to those of an Integrating Sandwich Spectrophotometer (ISSW), an instrument with a rich history of such measurements. Laboratory standards of particulate number and mass concentration in liquid were used to assess the performance of each instrument independently. Laser transmission spectroscopy (LTS) was used to confirm particulate number concentration in some samples. Additionally, snow samples from Russia, Greenland, and China were tested with the ISSW and SP2. The direct results of this work lie in the procedural development for using the SP2 to determine BC-in-snow with quantifiable uncertainty, and in the assessment of the ISSW accuracy. The instrument comparison suggests that the ISSW BC concentration estimates are biased high. The larger impacts of this work will derive from the stronger constraints on BC concentration-in-snow that it promises.