Global spatial and temporal variations of gravity-wave-induced heat fluxes and heating rates based on SABER's observations

Abstract. Gravity waves (GWs) play an important role in balancing the energy budget of the mesosphere and lower thermosphere (MLT) by heating/cooling the background atmosphere. The global heat fluxes and heating rates generated by non-breaking GWs are derived from SABER observations during 2002–2025. The derived heat fluxes are mainly downward and cool the background atmosphere, with peaks occurring at 80–100 km. Around 35 °N, the monthly mean heat flux and heating rate are ~−0.7 Kms⁻¹ and ~−12 Kday⁻¹, with standard deviations of ~1.1 Kms⁻¹ and ~20 Kday⁻¹, respectively. Global GW-induced heat fluxes and heating rates exhibit stronger annual and weaker semiannual oscillations, with the stronger peak in summer hemisphere. Moreover, these quantities show notable interhemispheric and seasonal asymmetries, with larger summer amplitudes occurring at the northern high latitudes. Such interhemispheric asymmetry agrees with the colder summer mesopause at northern high latitudes. However, the heat fluxes and heating rates derived here are ~0.3−0.5 times the values lidar observations and are ~0.5 times the theoretical values and breaking GWs. These underestimations are induced by the uncertainties of GW propagation directions, observational filter, and limited GW wavelengths observable by SABER.