During the first operational year of the Balloon Baseline Stratospheric Aerosol Profiles (B2SAP) project in 2020, 24 instrumented balloons were launched from Boulder, at the NCAR Marshall Field Site, to measure vertical profiles of water vapor (WV), ozone (O3), and aerosol number and size distribution (140 nm – 2.5 µm) from the surface to the middle stratosphere (~28 km). These soundings complement the NOAA Global Montoring Laboratory (GML) multi-decadal program of routine balloon launches from Boulder to monitor stratospheric ozone and water vapor, as well as the more recently developed program of coordinated launches by CSL and GML for SAGE III/ISS satellite retrieval validation from Boulder and Lauder, New Zealand. The intention is to continue at least this frequency of launches for 4 years, and add new stations when possible.
The in situ measurements collectively provided by these balloon soundings at Boulder and other locations provide a unique dataset that documents the background state of Earth's stratosphere and provides insight into variability in the stratospheric aerosol size distribution that is difficult to constrain from satellite observations. In these profile measurements, we have observed the effects of multiple stratospheric injection events, from intense Siberian and Australian wildfires and by moderate volcanic eruptions, that perturbed the stratospheric aerosol loading. The ongoing measurements will help us to better understand how these natural events alter stratospheric composition, especially the number and size distribution of aerosols, and how these perturbations evolve with time.