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Dynamical downscaling of climate projections in the tropics
  • Shuchang Liu,
  • Christian Zeman,
  • Christoph Schär
Shuchang Liu

Corresponding Author:shuchang.liu@env.ethz.ch

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Christian Zeman
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Christoph Schär
ETH Zurich
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The long-existing double-ITCZ problem in Global Climate Models (GCMs) hampers accurate climate simulation. Using a regional climate model (RCM) over the tropical and sub-tropical Atlantic with a horizontal resolution of 12 km and explicit convection, we develop a bias-correction downscaling methodology to remove GCM biases. The methodology is adapted from the pseudo-global warming (PGW) approach, typically used to exert the climate-change signal to a reanalysis-driven RCM simulation. We show that the double ITCZ problem persists with conventional dynamical downscaling, but with our bias-corrected downscaling, the double ITCZ problem is removed. Detailed analysis attributes the main cause of the double ITCZ problem of the selected GCM to the sea surface temperature (SST) bias. Compared to the GCM’s AMIP simulations, RCMs with higher resolution allow explicit deep convection and enable a better simulation of tropical convection and clouds. The developed methodology is promising for constraining climate sensitivity by removing double-ITCZ biases.
10 Aug 2023Submitted to ESS Open Archive
12 Aug 2023Published in ESS Open Archive