Objectives: To investigate the influence of SST anomalies on the variability of monsoon climates, in particular the role of ENSO with the aim of raising awareness of the processes which must be well simulated by models before climate change predictions for the tropics can be judged useful.

Work description:

UREADMY with ICTP: Various aspects of the influence of regional SST anomalies on the development of rain-bearing circulation systems in the tropical regions will be studied by means of sensitivity experiments with atmospheric and regional coupled models. Specifically, these experiments will investigate the influence of springtime SST anomalies in the West Pacific and Indian Ocean on the development of the Asian summer monsoon.

MPG.IMET: The ENSO/monsoon relationship will be further investigated on annual and interdecadal time scales using results from uncoupled and coupled climate integrations. Observational data will be used to validate findings from model simulations.

The Met. Office: Carry out sensitivity experiments with idealised El Niño/La Niña SST anomalies to investigate the mechanisms of the monsoon response and how this is dependent on improvements to the parametrization of tropical convection.

The Met. Office: An important link between SSTs in the Mediterranean and summer Sahel rainfall has recently been discovered, but is not yet included in long-range prediction techniques. Sensitivity experiments will be designed to further test the strength of this influence, and will be used to understand its mechanisms. The causes and mechanisms of climate variability in the Caribbean will also be investigated, where possible focusing on the primary growing seasons.

Deliverables:

D1201: Assessment of the sensitivity of the tropical circulation and the associated hydrological cycle to regional SST anomalies, including idealized El Niño/La Niña forcing.

D1202: Report on the causes of interannual variability of monsoon rainfall over tropical North Africa and the Caribbean.

Milestones:

Year 1: Experimentation on the impact of regional SST anomalies on tropical North Africa and the Asian summer monsoon, including idealized El Niño/La Niña integrations.

Year 2: Diagnostic analysis of experiments performed in Year 1. Begin analysis of climate anomalies over the Caribbean, and design appropriate sensitivity experiments.

Year 3: Complete SST sensitivity experiments. Complete analysis of the causes and mechanisms of climate variability over the Caribbean. Complete report on investigation of changes in interannual variability and response to idealised SST anomalies.