Comment on essd-2026-147

<strong class="journal-contentHeaderColor">Abstract.</strong> Photolysis of HONO and O₃ in the troposphere is a primary source of OH radical and a fundamental control on atmospheric oxidative capacity. Their vertical distributions and diurnal evolution are therefore essential for elucidating photochemical processes in the planetary boundary layer and the lower free troposphere. Yet long-term, continuous observations of the vertical profiles of HONO, O₃, their photolysis frequencies, and the resulting OH production rates remain extremely limited, particularly at multi-regional and interannual scales. Here we present vertical profile measurements of HONO and O₃ acquired by the Chinese Hyperspectral Vertical Remote Sensing Network during 2021&ndash;2024. The dataset comprises 22 representative sites spanning urban, suburban, plateau, and basin environments, covering diverse surface and climatic regimes. Profiles extend from the surface to 4 km with ~100 m vertical resolution and ~15 min temporal resolution. Using the TUV model with co-retrieved aerosol and trace-gas profiles, we derive photolysis frequencies of HONO and O₃ and the corresponding OH production rates, P(OH)_HONO and P(OH)_O3. The observations reveal robust regional patterns in the diurnal and vertical structure of tropospheric photochemical activity. Photolysis frequencies peak near local noon and generally increase with altitude from the surface layer to the upper mixed layer and the lower free troposphere, whereas OH production rates reach their maxima within the boundary layer and decrease with height. Processed using a unified retrieval framework and rigorous quality control, this dataset provides quantitative constraints on the contribution of HONO and O₃ photolysis to tropospheric OH, supports improved radical parameterizations in chemical transport models, and enables synergistic multi-platform remote sensing analyses. By delivering the first systematic, long-term vertical profiles of HONO, O₃, and their OH production in China, this public dataset fills a critical observational gap and offers a robust basis for investigating the spatiotemporal evolution of tropospheric oxidative capacity across regions and altitude ranges, with substantial scientific significance and long-term applicability. The dataset is available for free at Zenodo (<a href="https://doi.org/10.5281/zenodo.18489836" target="_blank" rel="noopener">https://doi.org/10.5281/zenodo.18489836</a>, Zou et al., 2026).