A case study on the application of SCIAMACHY satellite methane measurements for regional studies: the Greater Area of the Eastern Mediterranean

Abstract

Many studies have focused on geological formations, such as mud volcanoes, which abound in the Greater Area of the Eastern Mediterranean (GAEM; 25° N–50° N, 5° E–55° E). This geological source is thought to provide a significant portion of the global methane (CH₄) emissions. However, studies in the GAEM have focused on specific locations rather than extensive areas, which has led to a gap in our understanding of the spatial and temporal variability of CH₄ atmospheric mixing ratios. Here, we present characteristics of methane loading over land in the GAEM using dry air columnar data (XCH₄) retrieved from SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Cartography) satellite measurements with the Weighting Function Modified Differential Optical Absorption Spectroscopy (WFM-DOAS) version 1.0 algorithm. We defined methane annual, seasonal and monthly spatial patterns over the area using 2003 and 2004 measurements. The annual mean XCH₄ levels over the study area were estimated to be 1761 ± 27 ppb for 2003 and 1758 ± 26 ppb for 2004. A seasonal variability with a summer–autumn peak was observed for both 2003 and 2004, August being the month with the highest methane concentrations. The northeastern part of the area exhibits the highest XCH₄ values while the high elevation regions defined by the triangle of eastern Turkey, the Persian Gulf and the Caspian Sea and the region of the eastern coast of the Red Sea exhibit the lowest levels. A latitudinal gradient was observed for the area during 2003 and 2004. A comparison of measured XCH₄ levels above two of the world's most renowned mud volcano regions situated in the GAEM with anticipated methane columnar concentrations as modelled for eruption cases shows that no mud volcano eruptions were observed from SCIAMACHY during 2003 or 2004.

Acknowledgements

This work was funded partly under the AMFIC Project of the European Commission (Aeronautics and Space STREP, Contract No. 030940).