Spatial variability of methane: attributing atmospheric concentrations to emissions

Area of Science:

• Atmospheric chemistry
• Environmental science
• Geospatial analysis

Background:

• Atmospheric methane (CH4) concentrations exhibit complex spatio-temporal patterns.
• Understanding methane sources and transport is crucial for climate change mitigation.
• Previous studies often lacked high-resolution spatial and temporal data in complex terrain.

Purpose of the Study:

• To quantify atmospheric methane concentrations in Switzerland.
• To identify spatio-temporal patterns and controlling factors of methane.
• To assess the utility of mobile measurements for emission inventory validation.

Main Methods:

• Utilized a mobile laser spectrometer and GPS for atmospheric methane quantification.
• Conducted measurements along transects in complex, agricultural terrain.
• Employed autocorrelation analysis to determine spatial information content of measurements.

Main Results:

• Identified three key factors influencing diurnal and regional methane patterns: source distribution, vertical exchange, and local wind patterns.
• Nighttime ground-level measurements provided information on regional methane sources up to 8.3 km.
• Daytime measurements were only informative for sources within 240 m upwind fetch.
• Nighttime concentrations better reflected emission inventory data and highlighted inconsistencies.

Conclusions:

• Measurement timing significantly impacts the spatial scale of information obtained about methane sources.
• Mobile laser spectrometry is effective for detailed methane source attribution in complex terrain.
• Nighttime measurements offer superior potential for validating and refining methane emission inventories.