Exploring discrepancies in observed vs. simulated mid-latitude precipitation trends

As we continue to pump CO2 and other greenhouse gases (GHGs) into the atmosphere, global average temperatures continue to rise and hydroclimate patterns, including precipitation, are shifting. Systematically quantifying precipitation changes, however, is challenging because the physical constraints of precipitation are not as well understood as those of temperature. Additionally, there is a large amount of internal variability associated with precipitation that adds to the challenge of quantifying precipitation trends. Finally, constraining precipitation projections are further complicated by the need to parameterize processes related to precipitation, like cloud formation and atmospheric convection, in state-of-the-art climate models. This study aims to understand why observed precipitation trends sometimes lie outside or at the edge of simulated precipitation trend distributions (i.e. the southwest and southeast United States and southeastern South America). To do this, we will employ the CESM2 Large Ensemble and quantify the thermodynamic vs. dynamic contributions to precipitation change across the Northern Hemisphere midlatitudes (20°N-60°N) based on a large-scale moisture budget. We hypothesize that the thermodynamic component of precipitation change will be relatively consistent across the Large Ensemble while variability in the dynamic component across ensemble members may elucidate potential biases within the Large Ensemble that might explain simulated vs. observed precipitation trend discrepancies.