The influence of vegetation on the ITCZ and South Asian monsoon in HadCM3 1Met Office, Hadley Centre, Fitzroy Road, Exeter, EX12NY, UK
22 Jun 2012
2Indian Institute of Tropical Meteorology, Pashan, Pune, 411008, India
Received: 20 Dec 2011 – Published in Earth Syst. Dynam. Discuss.: 06 Feb 2012 Abstract. The role of global vegetation on the large-scale tropical circulation is
examined in the version 3 Hadley Centre climate model (HadCM3).
Alternative representations of global vegetation cover from observations and
a dynamic global vegetation model (DGVM) were used as the land-cover
component for a number of HadCM3 experiments under a nominal present day
climate state, and compared to the simulations using the standard land cover
map of HadCM3. The alternative vegetation covers result in a large scale
cooling of the Northern Hemisphere extra-tropics relative to the HadCM3
standard, resulting in a southward shift in the location of the
inter-tropical convergence zone (ITCZ). A significant reduction in Indian monsoon
precipitation is also found, which is related to a weakening of the South
Asian monsoon circulation, broadly consistent with documented mechanisms
relating to temperature and snow perturbations in the Northern Hemisphere
extra-tropics in winter and spring, delaying the onset of the monsoon.
Revised: 09 May 2012 – Accepted: 22 May 2012 – Published: 22 Jun 2012
The role of the Northern Hemisphere extra-tropics on tropical climate is
demonstrated, with an additional representation of vegetation cover based on
DGVM simulated changes in Northern Hemisphere vegetation from the end of the
21st Century. This experiment shows that through similar processes the
simulated extra-tropical vegetation changes in the future contribute to a
strengthening of the South Asian monsoon in this model. These findings
provide renewed motivation to give careful consideration to the role of
global scale vegetation feedbacks when looking at climate change, and its
impact on the tropical circulation and South Asian monsoon in the latest
generation of Earth System models.
Citation: McCarthy, M. P., Sanjay, J., Booth, B. B. B., Krishna Kumar, K., and Betts, R. A.: The influence of vegetation on the ITCZ and South Asian monsoon in HadCM3, Earth Syst. Dynam., 3, 87-96, doi:10.5194/esd-3-87-2012, 2012.