Measuring methane at high-latitudes in winter and tropics year round with a laser.

Atmospheric methane (CH4) is the second most important anthropogenic greenhouse gas with a shorter lifetime but higher global warming potential then CO₂, making CH₄ an attractive target for climate change mitigation. However, data from current passive sensors cannot be used to adequately constrain important CH₄ sources (e.g., wetlands, rice) in monsoonal and from late fall to early spring in boreal areas. At Goddard Space Flight Center (GSFC) we have been developing the technology needed to remotely measure CH4 from airborne and space platforms, using lasers. Our CH₄ LIDAR is a nadir-viewing instrument that uses the strong laser echoes from the Earth's surface to measure CH₄. Our measurement technique uses Integrated Path Differential Absorption (IPDA), which measures the absorption of laser pulses by a trace gas and can make measurements, in sunlight and darkness, at all latitudes and can be relatively immune to errors introduced by scattering from clouds and aerosols. In this paper, we will present the status of the instrument and suggest a potential use of this capability in an airborne campaign, which could provide valuable data in boreal regions and for tropical wetlands. The airborne instrument measurements can be integrated with global coverage from active lidar missions in development, i.e., MERLIN, to assess accuracy and to inform atmospheric transport modeling efforts within the NASA GEOS framework. These data can contribute to an improved annual methane budget and enhance our understanding of annual and seasonal methane trends.