Clusters of Regional Precipitation Seasonality Change in the Community Earth System Model version 2

Abstract

The likely changes to precipitation seasonality with warming are both impactful and not well understood. This work aims to describe areas that experience similar changes to seasonal precipitation irrespective of the original underlying precipitation seasonality. We train a Self-Organizing Map on the difference between the seasonal cycle of precipitation in the past and in a high warming future climate as represented by the Community Earth System Model version 2 to create regions with similar changes in precipitation seasonality. This method is applied separately over land and ocean surfaces because of the differing processes leading to precipitation over each. This method indicates that future changes in seasonal precipitation are most varied in the tropics because of a southward shift in the Inter-Tropical Convergence Zone. The seasonal shifts found over midlatitude oceans indicate a poleward shift in atmospheric river activity. We find a correspondence between certain land-based precipitation changes and Köppen climate classification. The seasonality of large-scale and convective precipitation is examined for each region. The relationship between the seasonal changes to precipitation and associated atmospheric processes are discussed. These processes include: atmospheric rivers, the inter-tropical convergence zone, tropical cyclones, and monsoons.