Abstract Zhao et al. (2025, https://doi.org/10.1029/2024GL112332) present a novel method to derive the optical fractal dimension (Df ${D}{f}$) of ambient black carbon (BC) aggregates using mobility diameters and mass concentrations. Sorensen et al. (2025, https://doi.org/10.1029/2025GL116124?af=R) argues that the BC Df ${D}{f}$ can also be derived from its optical scattering signals. We agree with Sorensen et al. (2025, https://doi.org/10.1029/2025GL116124?af=R) that the BC Df ${D}_{f}$ with a diameter >1.4 μm ${\upmu }\mathrm{m}$ can be derived from optical scattering signals. However, challenges remain for accurate online measurement of ambient BC, particularly for aggregates with diameters below 1,000 nm, as the applicability of power law relationships between wave vector and scattered intensity is unclear. Future research should focus on refining these measurements to address uncertainties and improve applicability.
Observations from the Little Bunker
Last updated: October 16, 2025 02:57 AM
Atmospheric CO₂
424.4 ppm
+18.2
ppm/year
Atmospheric CH₄
1933.54 ppb
+12.29
ppb/year
Global Temperature
+1.48 °C
Peak: +1.73°C
World Population
8.1 billion
+67
million/year