Reply to Comment by Sorensen Et Al. On “Could We Achieve the On‐Line Measurements of the Optical Fractal Dimensions of Black Carbon?”

Zhao et al. (2025, https://doi.org/10.1029/2024GL112332 ) present a novel method to derive the optical fractal dimension () 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 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 with a diameter >1.4 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.