Tropical cyclones (TCs) are an imminent danger to populations in their path, bringing strong wind, heavy rain, and storm surge. Past TCs have caused great damage in China, especially along the southeastern coastline. Meteorologists are concerned that the effects of global warming may change how these storms impact human populations.
Scientists use global climate models (GCMs) in climate change studies to simulate future changes in temperature, precipitation, etc. However, they are difficult to develop, they are resource intensive, and many models cannot properly simulate small-scale weather and climate systems like TCs, due to their coarse resolutions. This means that they cannot capture all the dynamic processes within a TC.
Prof. GAO Xuejie, from the Climate Change Research Center at the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences (CAS), is a corresponding author of a new TC modeling study published in Advances in Atmospheric Sciences
, along with a team of collaborators. Their research highlights ways to use regional climate models (RCMs) rather than GCMs to better simulate TC activity through the rest of the century.
"Recently, we conducted an unprecedented new set of RCM (RegCM4) simulations at 25-km grid spacing driven by five global models over East Asia." said GAO. "This provides a good opportunity to conduct the studies on the topic of TCs in the western North Pacific (WNP), which is the most active basin of TC activity."
The team began by evaluating the performance of RegCM4 model, which reproduced recent and present-day TC activity throughout the WNP. They found that the model successfully reproduces the major features of observed TC activity throughout the region.
"…although with underestimation of their intensity as most climate models did," stated GAO. Recent studies have stated that future TC intensity is the most difficult variable for models to simulate.
Data also suggests that by the end of the 21st century, the annual mean frequency of TC genesis and occurrence frequency is projected to increase, by 16% and 10%, respectively. Even with models undercalculating future TC intensity, simulated TCs tend to be stronger. Additionally, RCM projections indicate more TC landfalls within most coastal provinces of China, with an increase of ~18% over the whole Chinese territory.
"There are still large uncertainties in projecting future changes in TC activity, due to the limitation of the current climate models, and complexity of the TC systems, particularly concerning their genesis and occurrence." said GAO. "But most climate models agree with the increased intensity of future TCs, indicating higher risks associated with TCs in the future."
Reference: Wu, J., X. J. Gao, Y. M. Zhu, Y. Shi, and F. Giorgi, 2021. Projection of the future changes in tropical cyclone activity affecting East Asia over the western North Pacific based on multi-RegCM4 simulations. Advances in Atmospheric Sciences. http://doi.org/10.1007/s00376-021-0286-9.
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