image: Figure JJA circulation anomalies during 1922–1932. Shaded colors represent the geopotential height anomaly at 500 hPa. Gray lines represent the geopotential height anomaly at 200 hPa. Arrows represent the wind vector anomaly at 850 hPa. view more
Credit: ©Science China Press
This study is led by Prof. Jinming Feng (Institute of Atmospheric Physics, Chinese Academy of Sciences) and Dr. Meng Luo (Yunnan Climate Center). Various data and numerical simulations were combined to reveal the specificality and potential cause of a persistent dry period with significant social impact in history during the 1920s in Eastern China. The researchers found that during the 1920s, most regions in Eastern China suffered from less summer precipitation and high temperature. Given its spatial coverage, duration, and strength, the 1920s drought was unique for the 20th century.
Unlike previous studies which usually use the climate proxy records, this study employed the numerical simulations for the attribution analysis. Another innovation point in this study was the usage of the Regional Climate Model (RCM) other that the global-scale General Circulation Models (GCMs). “Our results proofed that the RCM had better performance than GCMs in simulating this drought event,” Luo says.
The numerical simulation consist of three regional downscaling experiments, and neither the antropogenic forcing experiment nor the natural forcing experiment could reproduce the spatial coverage and strength of this drought. However, after removing the forcing signals from the all-forcing control experiment, the internal climate variability modes showed similar patterns with the all forcing experiment. “It means the internal climate variabilities were the main drivers of this persistent drought,” Feng says.
Further study showed that this drought was most likely caused by the composite impact of the Atlantic Multidecadal Oscillation, the Pacific Decadal Oscillation, and the Indian Ocean Basin Mode. Such internal climate modes could led to strong land-sea thermal contrast and deeply high pressure anomaly circulation system in East Asia, thus suppressing the ascending movement and water vapor transport in this region.
“This study reveals that rather than human influence and natural forcing such as volcano eruption or solar radiation, the climate system itself can also triggers a persistent dry period which lasts for more than ten years,” Feng says.
See the article:
Luo M, Feng J, Xu Z, Wang J, Dan L. 2022. Numerical simulation and cause analysis of persistent summer drought during the 1920s in eastern China. Science China Earth Sciences, 65(5): 966–982, https://doi.org/10.1007/s11430-021-9891-9
Journal
Science China Earth Sciences