Process-oriented evaluation of the West African Monsoon system in CORDEX-CORE regional climate models

Improving the simulation of the West African Monsoon (WAM) system is paramount to increasing confidence in the projections of the region’s monsoon rainfall change. This work aims to thoroughly analyze the representation of the WAM system in two state-of-the-art, high-resolution (~25 km) regional climate models (RCMs) in order to highlight the causes of models’ biases through a process-oriented evaluation approach. Model results generally feature a north (Sahel) - south (Guinea Coast) dipole-like rainfall bias, although, sometimes, positive or negative rainfall biases are evident almost over the whole of West Africa. Our analysis shows that biases in the sea- and land-surface temperature on the one hand, and biases in the sea-level and land-surface pressure, on the other hand, lead to biases in the simulated temperature and pressure contrasts between the west African landmass and the eastern Atlantic ocean. The modeled equatorward or northward shifting of the AEJ is likewise found to contribute to the models' wet or dry biases over the Sahel. Finally, there is no consistency between models and reanalyses on the one hand, and between RCM experiments on the other hand, in the way, the simulated atmospheric instability/stability modulates the convection, especially over the Sahel.

TAMOFFO TCHIO Alain;  DOSIO Alessandro;  AMEKUDZI Leonard;  WEBER Torsten; 

2023-10-18

SPRINGER

JRC128333

0930-7575 (online),   

https://link.springer.com/article/10.1007/s00382-022-06502-y,    https://publications.jrc.ec.europa.eu/repository/handle/JRC128333,   

10.1007/s00382-022-06502-y (online),