Measurement report: Validation of multi-satellite remote sensing products and potential source apportionment of BrO and IO in the Arctic using ship-based DOAS

Arctic reactive halogen species are pivotal in mediating polar air-sea interactions and global biogeochemical cycling. Based on ship-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations from the 12th Chinese National Arctic Research Expedition (July to September 2021), this study provides a systematic performance assessment of Tropospheric Monitoring Instrument (TROPOMI), Geostationary Environmental Monitoring Spectrometer (GEMS), and Global Ozone Monitoring Experiment-2 (GOME-2) satellite products in the Arctic (R>0.6). Our findings indicate that tropospheric BrO variability is predominantly governed by sea-ice contact (SIC) duration, accounting for 48.63 % of the variance in a generalized additive model (GAM). Potential BrO source regions are identified in western Greenland, the high-latitude Canadian Arctic, and the marginal ice zone (MIZ). Implementing a dynamic boundary layer height (BLH) constraint enhanced the correlation from 0.73 to 0.77. Meteorological conditions exert significant modulation on activation efficiency. For instance, correlations reached 0.84 under southwesterly flow, whereas snowfall reduced the correlation from 0.87 during snow-free periods to 0.61 during snowfall events. Conversely, IO spatial variability is primarily driven by marine biogenic emissions, exhibiting a positive correlation with chlorophyll a concentrations (R = 0.64) and clustering in phytoplankton-rich regions such as the Bering Strait. In the MIZ, the moderate correlation between BrO and IO (R = 0.5) suggests their co-evolution at the shared ice-ocean-atmosphere interface. These high-resolution datasets provide critical a priori constraints for chemistry models. They optimize polar emission parameterizations and halogen budgets, improving Weather Research and Forecasting with Chemistry (WRF-Chem) predictions for polar processes and global climate assessment robustness.