Seasonal Distribution of Gravity Waves Near the Stratopause in 2019-2022

The cloud imaging and particle size (CIPS) instrument onboard the Aeronomy of Ice in the Mesosphere satellite provides images of gravity waves (GWs) near the stratopause and lowermost mesosphere (altitudes of 50-55 km). GW identification is based on Rayleigh Albedo Anomaly (RAA) variances, which are derived from GW-induced fluctuations in Rayleigh scattering at 265 nm. Based on 3 years of CIPS RAA variance data from 2019 to 2022, we report for the first time the seasonal distribution of GWs entering the mesosphere with high (7.5 km) horizontal resolution on a near-global scale. Seasonally averaged GW variances clearly show spatial and temporal patterns of GW activity, mainly due to the seasonal variation of primary GW sources such as convection, the polar vortices and flow over mountains. Measurements of stratospheric GWs derived from Atmospheric InfraRed Sounder (AIRS) observations of 4.3 mu m brightness temperature perturbations within the same 3-year time range are compared to the CIPS results. The comparisons show that locations of GW hotspots are similar in the CIPS and AIRS observations. Variability in GW variances and the monthly changes in background zonal wind suggest a strong GW-wind correlation. This study demonstrates the utility of the CIPS GW variance data set for statistical investigations of GWs in the lowermost mesosphere, as well as provides a reference for location/time selection for GW case studies. Aeronomy of Ice in the Mesosphere cloud imaging and particle size (CIPS) provides first near-global images of gravity waves at 50-55 km with high horizontal resolutionCIPS observes gravity wave hotspots generated by convection, topography, and the polar vortexLocations of gravity wave hotspots near the stratopause/lowermost mesosphere are similar to those in the mid-stratosphere near 35 km