Interhemispheric Anti-Phase Variability in Mesospheric Climate Driven by Summer Polar Upwelling During Solstice Months

Abstract. The upper mesosphere, a transition region between Earth's atmosphere and space, is characterized by complex interactions among water vapor (H2O), atomic hydrogen (H), ozone (O3), atomic oxygen (O), and temperatures. Using MLS, SABER, and SOFIE satellite data, we explore the upwelling-driven interannual variability of temperatures near 90 km (T90) and atmospheric constituents during solstice months, revealing a bottom-up control mechanism of “upwelling–H2O(H)–O3(O)–T90” in the two hemispheres. First, summer polar upwelling transports H2O upward, which is then transported toward the winter hemisphere by meridional winds. Subsequently, the hydration increases H via photolysis and depletes O3 in the winter hemisphere through H-driven catalytic loss. The O varies in pace with O3 due to chemical equilibrium, and the radiative and chemical heating by O/O3 reactions reduces the T90 in the winter hemisphere (T90W). Second, upwelling-induced cooling promotes polar mesospheric cloud (PMC) formation, with ice particle growth blocking H2O transport and dehydrating heights above PMCs. This dehydration reduces H abundance, thereby decreasing H-driven O3 loss. Meanwhile, the colder temperatures directly increase O3 through ozone kinetics. The enhanced O3, together with the coupled O, collectively increase the summer polar temperatures above 90 km (T90S). This anti-phase interannual variability between hemispheres, mediated by PMC microphysics and H2O-O3 chemistry, establishes summer polar upwelling as a fundamental driver of mesospheric climate and highlights the importance of dynamical-chemical coupling in the upper mesosphere.