First high-resolution BrO column retrievals from TROPOMI

For more than 2 decades, satellite observations from instruments such as GOME, SCIAMACHY, GOME-2, and OMI have been used for the monitoring of bromine monoxide (BrO) distributions on global and regional scales. In October 2017, the TROPOspheric Monitoring Instrument (TROPOMI) was launched on board the Copernicus Sentinel-5 Precursor platform with the goal of continuous daily global trace gas observations with unprecedented spatial resolution. In this study, sensitivity tests were performed to find an optimal wavelength range for TROPOMI BrO retrievals under various measurement conditions. From these sensitivity tests, a wavelength range for TROPOMI BrO retrievals was determined and global data for April 2018 as well as for several case studies were retrieved. Comparison with GOME-2 and OMI BrO retrievals shows good consistency and low scatter of the columns. The examples of individual TROPOMI overpasses show that due to the better signal-to-noise ratio and finer spatial resolution of 3.5×7&thinsp;km2, TROPOMI BrO retrievals provide good data quality with low fitting errors and unique information on small-scale variabilities in various BrO source regions such as Arctic sea ice, salt marshes, and volcanoes.</p

Investigation of meteorological conditions and BrO during ozone depletion events in Ny-Ålesund between 2010 and 2021

During polar spring, ozone depletion events (ODEs) are often observed in combination with bromine explosion events (BEEs) in Ny-Ålesund. In this study, two long-term ozone data sets (2010–2021) from ozonesonde launches and in situ ozone measurements have been evaluated between March and May of each year to study ODEs in Ny-Ålesund. Ozone concentrations below 15 ppb were marked as ODEs. We applied a composite analysis to evaluate tropospheric BrO retrieved from satellite data and the prevailing meteorological conditions during these events. During ODEs, both data sets show a blocking situation with a low-pressure anomaly over the Barents Sea and anomalously high pressure in the Icelandic Low area, leading to transport of cold polar air from the north to Ny-Ålesund with negative temperature and positive BrO anomalies found around Svalbard. In addition, a higher wind speed and a higher, less stable boundary layer are noticed, supporting the assumption that ODEs often occur in combination with polar cyclones. Applying a 20 ppb ozone threshold value to tag ODEs resulted in only a slight attenuation of the BrO and meteorological anomalies compared to the 15 ppb threshold. Monthly analysis showed that BrO and meteorological anomalies are weakening from March to May. Therefore, ODEs associated with low-pressure systems, high wind speeds, and blowing snow more likely occur in early spring, while ODEs associated with low wind speed and stable boundary layer meteorological conditions seem to occur more often in late spring. Annual evaluations showed similar weather patterns for several years, matching the overall result of the composite analysis. However, some years show different meteorological patterns deviating from the results of the mean analysis. Finally, an ODE case study from the beginning of April 2020 in Ny-Ålesund is presented, where ozone was depleted for 2 consecutive days in combination with increased BrO values. The meteorological conditions are representative of the results of the composite analysis. A low-pressure system arrived from the northeast to Svalbard, resulting in high wind speeds with blowing snow and transport of cold polar air from the north.</p

Atmospheric and Surface Processes, and Feedback Mechanisms Determining Arctic Amplification: A Review of First Results and Prospects of the (AC)3 Project

Mechanisms behind the phenomenon of Arctic amplification are widely discussed. To contribute to this debate, the (AC)3 project has been established in 2016. It comprises modeling and data analysis efforts as well as observational elements. The project has assembled a wealth of ground-based, airborne, ship-borne, and satellite data of physical, chemical, and meteorological properties of the Arctic atmosphere, cryosphere, and upper ocean that are available for the Arctic climate research community. Short-term changes and indications of long-term trends in Arctic climate parameters have been detected using existing and new data