African Low-Level Jets and Their Importance for Water Vapor Transport and Rainfall
Abstract
Uncertainty in the future evolution of tropical rainfall is linked to circulation changes under warming. In Africa, a key barrier to interpreting rainfall changes is our limited understanding of water vapor transport across the continent. Here, we show that a series of nocturnal easterly Low-Level Jets (LLJs), which form in the valleys punctuating the East African rift system, transport the majority of water vapor to central Africa from the Indian Ocean. There is a robust connection between strengthened LLJs and drought in eastern and southern Africa at interannual timescales, mediated by an increase in low-level divergence and water vapor export. Analysis of climate model simulations at a wide range of resolutions (250-4.5 km) suggests that grid lengths <60 km are needed to simulate the salient structures of LLJs. The failure of coarse resolution models to capture LLJs is linked with biases in rainfall climatology and variability across the continent.
- Publication:
-
Geophysical Research Letters
- Pub Date:
- January 2021
- DOI:
- 10.1029/2020GL090999
- Bibcode:
- 2021GeoRL..4890999M
- Keywords:
-
- climate model;
- low-level jet;
- precipitation;
- topography;
- Turkana Jet;
- Zambezi Jet