The Mei-Yu front, or a relatively stable meteorological zone stretching from the east coasts of China and Taiwan to southern Japan, serves as a barrier between Arctic and tropical circulation and plays a large role in determining tropical and subtropical weather and climate, including East Asian summer monsoons. During the summer in this region, the weather conditions are controlled by large-scale atmospheric patterns (more than 1,000 km long) that transport moisture and precipitation. The variability of these summer patterns with rising global temperatures is largely unknown. A new study, funded in part by the Climate Program Office’s Climate Variability & Predictability (CVP) Program, provides a theoretical framework to describe the moisture and precipitation processes along the Mei-Yu front and characterize perturbations to the patterns. The results, published in the Journal of Climate, provide specific atmospheric conditions that lead to variability in climate and weather, including vertical and horizontal movement and orientation of air and moisture, moisture circulation feedback loops, and energy sources. The researchers, Guang Yang and CVP-supported Tim Li of the University of Hawai‘i at Manoa, found strong agreement between their framework and observations along the Mei-Yu front, providing evidence that though their work was based on simple physical processes, it is a good approximation for atmospheric variability in this region. Further studies on variability of this scale are necessary to understand how the profound impacts of summer weather patterns in the tropics and subtropics may change with global warming.
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