In This Space
Methane emission Monitoring
Image credit: ESA
Atmospheric methane (CH4) is the second-most abundant anthropogenic greenhouse gas (GHG) after CO2. During shale gas field development, unexpected emissions of methane and other light gases can occur. Knowledge of background and industrial emissions helps to meet emissions guidelines. For example, in the USA, the Environmental Protection Agency (EPA) regulates emissions from the oil and gas sector, and methods are issued for in situ measurement.
Satellite EO-based quantification of methane in the troposphere is a new area of research. Airborne hyperspectral systems, such as: MAMAP, AVIRIS-ng, HyTES, and CARVE demonstrate the future potential. Several EO sensors have been tested. The SCIAMACHY instrument on board the ENVISAT satellite acquired CH4 monitoring data for seven years, and was a ground-breaking technology development platform. The sensor estimated total CH4 quantity of the at-nadir atmospheric column through modelling based on direct measurements of short-wave infrared (SWIR) radiation. Overall, the research reveals limitations in methane retrievals and deviations from validation data, as well as the relatively coarse spatial resolution of the observations (individual SCIAMACHY pixels are 30 km × 60 km, while some derived models average the data to a regular 1° longitude × 1° latitude grid).
The newer, operational TANSO Fourier Transform Spectrometer (FTS) sensor on board the Japanese Greenhouse Gases Observing SATellite (GOSAT) is dedicated to greenhouse gas monitoring. TANSO-FTS operates in the SWIR and thermal infrared (TIR) regions of the electromagnetic spectrum. SWIR measurements allow for the retrieval of CH4 column concentrations with high sensitivity near the Earth’s surface.
In 2015, a novel instrument operating in the SWIR region will be launched aboard the GHGSat nanosatellite. It will have unprecedented spatial resolution (tens of meters) and sensitivity equal to or better than any existing or previous SWIR satellite instruments. Using a novel observational paradigm, the GHGSat instrument will retrieve both total CH4 values (through depth of atmosphere columns) and local emission rates for identifiable CH4 emission sources. GHGSat will also measure CO2 emissions.
In 2017 a new EO system dedicated to methane monitoring will be launched. The Methane Remote LiDAR Mission (MERLIN) Integrated Path Differential Absorption (IPDA) LiDAR will measure total-column CH4 with high accuracy, and represents a new approach to atmospheric monitoring – MERLIN will be a micro-satellite launched into a polar orbit by DLR and CNES. Mission planners expect CH4 concentration measurements at better than 2% error, even under cloudy or variable illumination conditions. In contrast to existing passive remote sensors, measurements in polar regions will be possible and biases due to aerosol layers and thin ice clouds will be minimised. Further, the LiDAR instrument will allow retrieval of methane fluxes in all seasons and at night time.
Methane emissions can be attributed to different sources (e.g., livestock, oil and gas, and mining) and are also dependent on land cover type, and are particularly affected by wetlands. Wetland extent and land use information can be used to improve the accuracy of methane emission maps.
The methane emissions monitoring product can currently deliver archived and operational regional scale methane estimates (raster image values) along with summary statistics. Significant short-term improvements in accuracy are expected due to the scheduled launch of new sensors and the development of new operational analytical methods.
Known restrictions / limitations
Lifecycle stage and demand
Pre-License: Baseline/background levels of methane emissions and sources are potentially useful.
Exploration/Development: Baseline/background levels of methane emissions and sources are important to determine how hydraulic fracturing may impact natural leakage rates. Monitoring during exploration is required.
Production: Extensive air monitoring is needed to determine how hydraulic fracturing may impact methane natural leakage rates. Detection of unexpected methane leakage. In-situ monitoring and airshed modelling using complimentary data.
Environmental monitoring: Detection of unexpected methane leakage on a regional basis. Complimentary data to in-situ monitoring and airshed modelling.
Geographic coverage and demand
Demand and coverage is global.
Input data sources
Spatial resolution and coverage
The spatial resolution of satellite-based products is relatively coarse and in the range of 0.5‑60 km.
Individual SCIAMACHY pixels are 30 km × 60 km. Some of the models average the data to a regular 1° longitude × 1° latitude grid.
Minimum Mapping Unit (MMU)
Accuracy / constraints
The SCIAMACHY CH4 data set can be characterized by a single ground pixel retrieval precision of about 1.7%. The airborne MAMAP sensor provides total column relative accuracy of <≈1% on scales of several kilometres for clear sky atmospheric conditions.
Accuracy assessment approach & quality control measures
In all methane emission retrieval programs, ground measurement sites play a critical role in evaluating satellite data and retrieval models; targeted aircraft campaigns can also provide verification and better understanding of source regions.
Frequency / timeliness
Observation frequency: Global monthly mean maps are available from January 2003 to April 2012 (SCIAMACHY) and from June 2009 to September 2012 (GOSAT). Methane flux inversions (MACC project) are available for the period July 2009 to June 2013.
Timeliness of delivery: Following model development and calibration, products are made available immediately, e.g., on a monthly basis.
Archived SCIAMACHY data are available from ESA. GOSAT data are distributed by JAXA. Methane products are also available from the Tropospheric Emission Monitoring Internet Service (TEMIS).
Delivery / output format
# of Pages:
Internal – Project consortium and science partners
External – ESA
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