Troposphere-Mesosphere Coupling by Convectively Forced Gravity Waves During Southern Hemisphere Monsoon Season as Viewed by AIM/CIPS

A new data set consisting of Rayleigh Albedo Anomaly variance RAAv data resulting from measurements by the Cloud Imaging and Particle Size instrument on the Aeronomy for Ice in the Mesosphere satellite is introduced, and is used to illustrate the lower-mesospheric (similar to 50-55 km) gravity wave (GW) response to tropospheric convection during Southern Hemisphere monsoon season (December-February). The RAAv correspond to GWs with vertical wavelengths > 15 km and horizontal wavelengths between about 23 and 600 km. It is shown that these scales encompass most of the convectively generated GW spectrum at similar to 50-55 km altitude due to both plume overshoot and diabatic heating, and include those GWs most likely to impact the overlying ionosphere-thermosphere-mesosphere system. The GWs originate from convective sources associated with the African and South American land masses, the maritime continent/Australia, and the South Pacific Convergence Zone. The regions of enhanced convection are identified according to half-hourly rainfall rate (RR) distributions from the Global Precipitation Measurement mission. The GW RAAv exhibits spatial, inter-monthly, and inter-annual variabilities connected with RR and propagation conditions. A similar to 15 degrees southward shift of longitudinal structures in RAAv with respect to RR longitudinal structures is interpreted in terms of wave focusing toward the middle atmosphere summer easterly jet core. For the South American Monsoon System, a linear regression analysis shows RAAv variability to be expressible in terms of upper-stratosphere zonal wind speeds (correlation coefficient R = -0.91) with magnitude of RR playing a much lesser role (R = 0.16).