A strong seesaw pattern exists between the interannual variability of upper- and lower-level cross-equatorial flows (CEFs) over the Maritime Continent and Indian Ocean in boreal summer, according to a recently published study in Advances in Atmospheric Sciences by PhD candidate ZHAO Xiaoxuan and Prof. LU Riyu from the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences.
CEF refers to the airflow across the equator. During boreal summer in the Eastern Hemisphere, southerlies prevail in the lower troposphere, characterized by several branches, while well-organized northerlies prevail in the upper troposphere.
This characteristic of CEFs determines its important position in the interhemispheric exchange of mass and energy. Meanwhile, CEFs play a crucial role in modulating monsoon rainfall. Besides, the CEF over the Maritime Continent is also regarded as a significant factor contributing to the climate variability in the western North Pacific and East Asia.
"In previous studies, compared with the wide attention paid to the lower-level CEFs, the upper-level CEFs, especially their variability, have basically been ignored," said LU, corresponding author of the study. "Integrated analyses of both the lower- and upper-level CEFs are necessary and should be helpful for a better understanding of CEF variability, particularly if there is a close relationship between the lower- and upper-level CEFs."
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