Dynamic pathway linking Pakistan flooding to East Asian heatwaves

Area of Science:

• Atmospheric Science
• Climate Dynamics
• Extreme Weather Events

Background:

• Historic flooding in Pakistan and record heatwaves in China occurred in July-August 2022.
• Similar extreme weather events have coincided between these regions over the past 44 years.
• The underlying mechanisms connecting these events were previously unclear.

Purpose of the Study:

• To investigate the dynamic mechanisms linking Pakistan's extreme weather events to East Asian heatwaves.
• To determine if this connection is intrinsic to the climate system or influenced by sea surface temperatures.
• To assess the potential for subseasonal prediction of these extreme events.

Main Methods:

• Analysis of observational data.
• Conducting a suite of atmospheric model experiments.
• Utilizing atmospheric model ensemble simulations.

Main Results:

• Upper-tropospheric divergent winds from Pakistan's convective heating create an anticyclone over China, causing heatwaves.
• This dynamic pathway is largely independent of global sea surface temperature forcing.
• The connection is most active in July-August due to high convective variability over Pakistan.

Conclusions:

• A clear dynamic link exists between Pakistan flooding and East Asian heatwaves via upper-tropospheric wave propagation.
• This connection is an intrinsic feature of the climate system.
• The identified mechanism and time delay offer potential for improved subseasonal extreme event prediction in East Asia.