How synergy between instrumental active and passive concepts may help estimating methane emissions
DRF: Thesis subject SL-DRF-21-0208
Methane (CH4) is a major greenhouse gas. Monitoring its emissions remains a challenge. Surface atmospheric measurement networks are too sparse to make it possible to quantify methane sources and sinks at the relevant spatio-temporal scales. Satellite instruments have therefore been developed but estimating fluxes at the regional scale requires a very high level of both accuracy and precision, small revisit times and an extensive spatial coverage. Passive measurements made by operational satellite missions since 2003 have been treated by inverse modeling of the radiative transfer to obtain CH4 data at a spatial resolution of about 0.5 to 10 km. Nevertheless, these data do not cover high latitudes and may be associated to significant errors dues to the errors on various parameters (aerosol profiles, topology, albedo, clouds…) during the inversion. In parallel, satellite MERLIN should make in 2024 the first active methane measurements, which answer to the limitations of passive observation (data available at high latitudes, reduced bias due to aerosols, topology…) but have specific drawbacks (measurements averaged over segments of several tenths of km). In this framework, ONERA and its partners develop new concepts of compact active and passive remote sensing instruments (spectro-imaging, lidars…) for the future generation of spatial sounders (2028).
The aim of this work is to analyze in which conditions and how much active and passive satellite data bring information to each other and how using them in combination could lead to reduced errors on retrieved methane fluxes at regional scales.
Start date of the thesis: 01/10/2020
Sciences de l’Environnement d’Île de France
Université de Versailles Saint-Quentin
LSCE-Orme, L’Orme des Merisiers, Bat 714, Point courrier 129 91191 Gif sur Yvette Cedex