Assessment of the Impact of the Atmospheric Gravity Waves on the GOMOS HRTP Validation Study
Iannone, Rosario Quirino1; Casadio, Stefano1; Saavedra de Miguel, Lidia1; De Laurentis, Marta1; Brizzi, Gabriele1; Dehn, Angelika2; Fehr, Thorsten2
1Serco, ITALY; 2ESA/ESRIN, ITALY
Analysis of temperature profiles as a function of spatial and temporal separation shows that stratospheric temperature variability is impacted by atmospheric gravity wave activity. Gravity waves generated by convection are known to provide an important contribution to the thermodynamic processes of the atmosphere. Vertically propagating from tropospheric regions, gravity waves can considerably influence momentum budgets by depositing their momentum to the large-scale flow in the upper troposphere as they are broken. More recently, the satellite temperature retrievals, together with innovative analysis methods, are often used to provide constraints for model parameterization, which can improve the treatment of these phenomena in climate-prediction models, as these atmospheric waves are common features in the thermal structure of the middle and upper atmosphere.
The purpose of this study is to analyse the characteristics of the atmospheric gravity waves detectable in the GOMOS (Global Ozone Monitoring by Occultation of Stars) High Resolution Temperature Profiles (HRTP). These are collected over altitudes ranging from 18 to 35 km, in the 2002 to 2012 time period. Onboard of the ESA/ENVISAT platform, the GOMOS instrument is a medium-resolution spectrometer operating in the ultraviolet-visible-near-infrared (UV-VIS-NIR) spectral range, and determines the atmospheric structure parameters temperature and density as a function of altitude using stellar occultations technique.
Following our new approach, based on the use of the ''Morlet'' wavelet transform (Torrence and Compo, 1998), it is possible to capture the vertical amplitude and phase of waves of very different size along the temperature profile. The wavy signal is estimated and subtracted to the original profile, thus providing a ''wave-free'' profile. The validation, carried-out by comparing GOMOS wave-free temperature profiles and gravity wave structures with correlative measurements made by ozonesondes (SHADOZ, http://croc.gsfc.nasa.gov/shadoz) in the 40S to 40N latitude range, will be discussed in detail. The results of the inter-comparison demonstrate that the proposed approach is very effective, particularly for the study of gravity waves, which are by nature non stationary and highly localised in space and time.