The tropical Indian Ocean matters for U. S. winter precipitation variability and predictability

Abstract

Abstract The El Niño-Southern Oscillation (ENSO) is the key predictor for operational seasonal climate prediction in the United States (U. S.). Compared with the impact of the tropical Pacific associated with ENSO, the role of the Indian Ocean on U. S. climate variability and predictability is less documented. In this work, we noted that the impact of the tropical Indian Ocean is stronger than the tropical Pacific on winter precipitation variability in a part of the southeastern contiguous U. S. (CONUS), mainly including Kentucky, Tennessee, Mississippi, and Alabama. Different from the north-south contrastive impact of ENSO, the influence of the Indian Ocean is confined to the southeastern CONUS. Basin-wide warming (cooling) in the tropical Indian Ocean is tied to above (below) normal winter precipitation in the southeastern CONUS. The observed relationship is reproduced in model forecasts and simulations. Physically, Indian Ocean heating anomaly communicates its influence by inducing a teleconnection from the Indian Ocean to the North Atlantic Ocean via the North Pacific. The connection provides an additional source of predictability of the winter precipitation in CONUS, and monitoring the heat condition in the Indian Ocean may benefit winter precipitation prediction in the southeastern CONUS.