The Yangtze Valley has experienced several disastrous rainfall events throughout the record rainy season of 2020. However, the mechanism of extreme precipitation upstream of the Yangtze River remains unclear.
Research by researchers at the Institute of Atmospheric Physics at the Chinese Academy of Sciences reveals that the activity of high potential vorticity (PV) systems in the eastern Tibetan Plateau should be responsible for more than normal rainfall, not just in western China. I made it. Even in eastern China.
The study was published in Quarterly magazine of the Royal Meteorological Society of England..
“The activity of high PV systems is characterized by significant diurnal cycles,” said Dr. Ma Tingting, lead author of the study. “And their formation is closely related to the thermal contrast between the atmosphere near the surface and the lower atmosphere.”
In the morning, after sunrise, surface sensible heat increases sharply, and non-adiabatic heating decreases with height. Therefore, PV weakens in the lower atmosphere and the formation of high PV systems is minimized. Increased turbulence increases evaporation near the surface, which in turn reduces adiabatic heating of the surface. At the same time, cloud formation increases adiabatic heating at about 400 hPa. As a result, a thermal contrast of less than 400 hPa leads to an increase in non-adiabatic heating with height, which favors the production of high PV systems.
Compared to climatology, excess water supply from the anomalous anticyclone in the northern Bay of Bengal was forced by the warming of the Indian Ocean in 2020, with stronger thermal contrast and enhanced activity in the high PV system of the Tibetan Plateau. Contributed to.
Researchers have also investigated the conditions under which high PV systems can move from the Tibetan Plateau. They found that it was the arrival timing of the high PV system on the eastern flank of the Tibetan Plateau that played an important role in the subsequent development of these systems. Early afternoon or evening arrivals generally involve the convergence of air and the supply of sufficient water vapor downstream of the Tibetan Plateau. This helps the system move from the Tibetan Plateau and affect downstream precipitation.
“Our results not only reveal multiscale interactions, but also record rainfall in the region through the high PV system of the Tibetan Plateau, despite the Indian Ocean being far from the Yangtze River. Explains how they are involved in. ” The corresponding author of the study, Professor Liu Yoshimin.
Tingting Ma et al, unusually warm sea surface temperature in the Indian Ocean, vigorous potential vorticity of the Tibetan Plateau, violent potential vorticity along the Yangtze River in the summer of 2020, Quarterly magazine of the Royal Meteorological Society of England (2022). DOI: 10.1002 / qj.4243
Chinese Academy of Sciences
Quote: The high potential vorticity system of the Tibetan Plateau was acquired from https: //phys.org/news/2022-02-high-potential-vorticity-tibetan on February 8, 2022, on the Janze River (February 8, 2022). Sun) Contributes to record rainfall in the surrounding area-plateau-contribute.html
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The high potential vorticity system of the Tibetan Plateau contributes to record rainfall around the Yangtze River.
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