Variability of Extreme Events in East Asia and their Dynamical Control: A Comparison Between Observation and Two High-Resolution Global Climate Models.

Abstract:

East Asia is submitted to a strong seasonal monsoon system, with dry winters and wet summers. Each season can be submitted to extreme weather events such as long drought spells or extreme daily rainfall. Because this region is densely populated, the understanding and predictability of such events is a major subject of concern in the framework of global warming scenario.

In this study we investigate the occurrence of the two (above mentioned) extreme events. We focus on their variability and the large-scale atmospheric (+ STT) patterns associated with these events. We use APHRODITE and PERSIANN observation, along with outputs from 2 high resolution (0.5 degree) global climate model (GCM): HadGEM3-GC2 (MetOffice, UK; fully coupled with ORCA025) and HiRAM-C192 (GFDL, USA; forced by prescribed SST). We use different approaches (composites and correlation fields) to highlight the main patterns and mechanisms that control the variability of extremes.

We focus on the 1975-2005 historical period. Despite some biases, models can reproduce the signal of extreme events and their dynamical control. Results show a strong control of the land-sea heat contrast along with a significant impact of the monsoon winds system. The SST (which translate the moisture source) does not have a significant impact when considering short terms (monthly) variability but has stronger impact in terms of internannual variability.

This work is then extend to end of century projection with the two GCM to investigate the major changes in the large scale dynamics and how it can impact extreme weather events.