Statistical properties of lower atmospheric gravity wave spectra derived from COSMIC measured temperature profiles

Knowledge of the global morphology of gravity wave sources in the lower atmosphere is critically important, but still lacking, for understanding gravity wave breaking in the middle atmosphere. The recent and ongoing measurements of atmospheric temperature in the lower stratosphere and upper troposphere derived from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission have continuous and global coverage with high vertical resolution and high quality in the lower atmosphere. This dataset allows us to systematically develop a global geographic and seasonal climatology of gravity wave energy spectra in the lower atmosphere. We use an efficient and well-behaved wavelet transform algorithm to process the large set of COSMIC temperature profiles and derive their statistical spectral characteristics. Preliminary results show that the spectral features of gravity wave activity near the equator are largely different from those at midlatitudes. There exists a spectral peak for perturbations with a long vertical wavelength at about 15 km altitude near the equator and also a distinct spectral peak near 18 km for the equatorial tropopause, indicating a persistent source of gravity wave activity that is mostly caused by convection. On the other hand, the spectral peaks near the midlatitude tropopause show a multi-layered structure, indicating different sources of wave activity. Spatial and temporal characteristics and variability of the gravity wave spectra in the lower atmosphere are presented.