The Global Monsoon Convective System as Reflected in Upper Atmosphere Gravity Waves

The concept of a global monsoon system collectively comprising 6 tropical regions is applied to Outgoing Longwave Radiation (OLR) as a proxy for convectively generated gravity waves (GWs), leading to the global monsoon convective system (GMCS). The six tropical regions are North and South Africa, Central and South America, and the South Asia-Pacific and Malay Archipelago/Australia-Pacific regions. The extended GMCS is considered in terms of gravity wave momentum fluxes (GWMFs) at 30, 50, 70, and 90 km altitude during the summer season in both hemispheres between December 2016, and August 2020. The GWMFs are inferred from TIMED/SABER temperature measurements. Intermonthly, interseasonal, and interannual variations in monthly mean GWMFs are interpreted in terms of OLR as a proxy for the spatial-temporal variability of GW sources, and in terms of MERRA2 zonal winds that quantify the influences of changes in background propagation conditions. It is found that temporal variations in GWMFs associated with the GMCS as a whole are not highly correlated with OLR, but at 30, 50, and 70 km are quantitatively linked to Doppler-shifting effects by local winds, wind filtering at 15 km altitude, and "instrument filtering." These effects are also compared and examined in the context of GW variances at 50 km in Southern Hemisphere summer measured by the CIPS instrument on the AIM satellite, which measures a different part of the GW spectrum. The SABER GWMF response at 90 km is irregular and variable, but sometimes consists of 3- and 4-peaked structures in longitude that may reflect nonmigrating tide influences on GW propagation conditions.