Relationship between the Subtropical Anticyclone and Diabatic Heating

Abstract

Monthly mean reanalysis data and numerical experiments based on a climate model are employed to investigate the relative impacts of different types of diabatic heating and their synthetic effects on the formation of the summertime subtropical anticyclones. Results show that the strong land surface sensible heating (SE) on the west and condensation heating (CO) on the east over each continent generate cyclones in the lower layers and anticyclones in the upper layers, whereas radiative cooling over oceans generates the lower-layer anticyclone and upper-layer cyclone circulations. Such circulation patterns are interpreted in terms of the atmospheric adaptation to diabatic heating through a potential vorticity?potential temperature view. A Sverdrup balance is used to explain the zonally asymmetric configuration of the surface subtropical anticyclones. The strong deep CO that is maximized in the upper troposphere over the eastern continent and the adjacent ocean is accompanied by upper-tropospheric equatorward flow and weaker lower-tropospheric poleward flow, whereas the very strong longwave radiative cooling (LO) that is maximized near the top of the planetary boundary layer over the eastern ocean is accompanied by strong surface equatorward flow and weaker upper-layer poleward flow. The center of the surface subtropical anticyclone is then shifted toward the eastern ocean, and its zonal asymmetry is induced. This study concludes that in the summer subtropics over each continent and its adjacent oceans LO, SE, CO, and a double-dominant heating (D) from west to east compose a LOSECOD heating quadruplet. A specific zonal asymmetric circulation pattern is then formed in response to the LOSECOD quadruplet heating. The global summer subtropical heating and circulation can then be viewed as ?mosaics? of such quadruplet heating and circulation patterns, respectively.