Giant sea salt aerosol (GSSA) particles are important for understanding how sunlight and clouds interact with Earth’s atmosphere. Scientists have measured these particles directly using specialized instruments on planes and ships, but these measurements are limited to certain times and places. To fill in the gaps, scientists often use global datasets called “reanalysis products,” which estimate the presence of particles like GSSA over time and space using source functions derived from the limited observations. Two widely used reanalysis datasets are NASA’s MERRA-2 and ECMWF’s EAC4, both of which estimate sea salt particle amounts at different heights in the atmosphere.

In this study, we compared those model-based estimates to actual measurements of GSSA from three field campaigns: VOCALS, SOCRATES, and ICE-T. We found that both MERRA-2 and EAC4 greatly overestimate the amount of GSSA, especially higher up in the atmosphere. This means that some climate studies using these datasets may be overestimating how much GSSA is in the air, which could affect conclusions about their role in climate and cloud formation. More accurate source functions for these particles are needed to better represent them in models and understand their impacts on the atmosphere.