Polar Stratospheric Clouds in Aeolus optical products as gravity wave tracers in the early polar winters

• Main Author: Cito Filomarino, Vittoria
• Format: Thesis
• Language: English
• Published: 2022
• Subjects: Lidar; South Pole; Aeolus; South pole
• Online Access: https://elib.dlr.de/190479/; https://elib.dlr.de/190479/1/Vittoria_Cito_Tesi_Msc_Environmental_Meteorology.pdf

The first Doppler Wind Lidar in space is the European Space Agency’s Earth Explorer Aeolus, launched in 2018: it has been measuring for more than 3 years wind profiles on a global scale, exceeding its expected lifetime. The mission successfully demonstrated that wind profiles obtained by a spaceborne DWL are of great benefit for Numerical Weather Prediction models improvement. Aeolus retrieves wind by measuring the Doppler shift in the laser beam reflected by a molecule or aerosol particle. The satellite is equipped with a single payload able to deliver near-realtime collocated profiles of wind and optical products. This thesis aims to highlight the unique opportunity that Aeolus products entail in the study of the dynamical aspects of cloud formation. Especially suited for this kind of study are Polar Stratospheric Clouds (PSCs), which have been observed from space as soon as the satellite era begun due to their important role in the ozone hole chemistry. Many studies show that Gravity Waves are an important trigger for PSC formation, especially in the early winter. In fact, in order to form, PSCs require very low temperatures, as low as −80◦ C, to condense the little water vapor present in the polar stratosphere. These temperatures occur every year over the South Pole, yet when these temperatures are just approach, GW-induced temperature perturbations become relevant as they may trigger PSC formation whereas synoptic scale temperatures would not allow it. Gravity waves are crucial in the climate system as they redistribute energy in the form of momentum, driving winds and weather patterns. Gravity waves are a small-scale perturbation due to vertical forcing of the main air flow. As such, they can arise from a variety of phenomena such as orographic lifting, tropospheric deep convection but also breaking of a planetary wave. There is a joint effort in building a Gravity Wave climatology, which would improve our ability to predict weather and climate patterns. This has mostly focused on well know hostspot of ...