EGU2020-1098
https://doi.org/10.5194/egusphere-egu2020-1098
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

South Asian summer monsoon in warm epochs of Mid-Holocene and end of 21st century; new insights from high resolution simulations

Lekshmi Mudra B1,2, Thazhe Purayil Sabin1,2, and Raghavan Krishnan1,2
Lekshmi Mudra B et al.
  • 1Indian Institute of Tropical Meteorology, Centre for Climate Change Research, Pune - 411008, Maharashtra, India
  • 2Department of Atmospheric and Space Sciences, Savitribai Phule Pune University, Pune - 411007, Maharashtra, India

The mid-Holocene (MH) was a warmer period, similar to the end of the 21st century climate under high emission realizations. The Indus valley civilization believed to be flourished under the expense of enhanced south Asian summer monsoon precipitation associated with the northward migration of the Inter Tropical Convergence Zone (ITCZ) during the mid-Holocene (MH). However, such an enhanced precipitation is not visible over the northwest India and Pakistan belt in future projection. The role of dynamical and various teleconnection factors behind the enhanced MH precipitation over the Indus valley region is still elusive due to the limitation of course resolution modelling efforts available so far as part of the various phases of Paleoclimate Modelling Intercomparison Projects (PMIP).  To overcome this limitation, we have designed high resolution Paleo-climate simulations using a state-of-the-art variable resolution global climate model (LMDZ: Laboratoire Meteorologie Dynamique and Z stand for zoom) which configured with a 35 km spatial resolution over the South Asian region. We conducted various sensitivity experiments to understand the role of dynamics and teleconnection in enhancing monsoon precipitation over the Indus valley in addition to the MH orbital conditions. Boundary conditions from the PMIP-3, CMIP5 and HadISST datasets utilized for various sensitive experiments. High resolution, clearly demonstrates value addition in simulating the enhanced MH precipitation over Northwest India and adjoining Indus basin associated with the northward migration of the ITCZ and shift in the ascending branch of Hadley cell. We explored the role of various oceanic and atmospheric factors responsible for this enhanced Indus valley precipitation through linearized moisture budget analysis and comparing the relative strength and position of Hadley cell. By further decomposing the thermodynamic and dynamic term into their advection and divergence component, we could demonstrate the role of moisture convergence due to the strengthened atmospheric circulation through the oceanic teleconnection, which additionally  plays a crucial role in enhanced MH precipitation comparing to the dynamical factors. Idealized simulation with the end of 21st century warm condition with the MH orbital forcing and various teleconnection patterns affirms that the thermodynamically induced future precipitation and circulation changes, may not be adequate to make a profound shift in the northern limit of the ITCZ towards its MH locale rather producing enhanced precipitation over the north Indian ocean and localized extreme precipitation over Indian landmass.

Keywords: Indus Valley civilization, Mid-Holocene, Monsoons, Teleconnection, ITCZ and Hadley circulation

How to cite: Mudra B, L., Sabin, T. P., and Krishnan, R.: South Asian summer monsoon in warm epochs of Mid-Holocene and end of 21st century; new insights from high resolution simulations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1098, https://doi.org/10.5194/egusphere-egu2020-1098, 2019