Low-Level Vertical Structure of Cross-Equatorial Flows in Boreal Summer

Abstract

Abstract Cross-equatorial flows (CEFs) are critical channels for mass, momentum, and water vapor exchange between the southern and northern hemispheres and have considerable influence on the global air-sea system. This study uses ERA-5 reanalysis data to find the relationship between vertical structure characteristics of global low-level CEFs in boreal summer and their correlation with sea surface temperature (SST). The research demonstrates that the vertical structure of CEFs is independent. The windspeed core is mainly at 925hPa or 1000hPa, and the vertical structure of CEFs has an obvious correlation. Through EOF analysis, two main vertical structures of the eastern hemisphere's CEFs are obtained: "consistent variation " and "opposite variation. " The vertical structures of the western hemisphere only have "opposite variation "and have greater longitude spans with tinner southerly wind thickness. The correlation analysis between CEFs and SST indicates Pacific Decadal Oscillation, two types of ENSO, and SST variations in the Indian and central Pacific oceans. SST variations can relate to the vertical structure change of CEFs.