Developing Accurate MethaneSAT Models
The MethaneSAT project, an ambitious initiative aimed at monitoring methane emissions, has shown promising results in its early stages. The project, which employs a hierarchy approach that includes both aircraft and ground-based instruments, has captured 97 measurements over various agricultural areas worldwide, including 13 over New Zealand, before it was lost in late June 2025.
At the helm of the MethaneSAT project is Dr Sara Mikaloff-Fletcher, the Principal Scientist (Carbon, Chemistry and Climate) at NIWA and the Science Leader for MethaneSAT. Her colleague, Dr Beata Bukosa, an Atmospheric Modeller at NIWA, plays a pivotal role in the project as well.
In situ (ground-based) methane measurements, such as those from dense networks like the Integrated Carbon Observation System (ICOS), provide direct, calibrated mole fractions of methane in the atmosphere. These measurements are used as inputs and constraints in atmospheric inversion models, which estimate methane emissions by optimizing modeled fluxes to best match these observations. This process helps to evaluate and improve methane emissions inventories on various scales, including national and regional levels.
Satellite and aircraft measurements, like those from the Total Carbon Column Observing Network (TCCON) and GOSAT, complement ground-based data by offering broader spatial coverage and height-resolved information. Integrating these retrievals with advanced retrieval algorithms allows models to capture spatial gradients and temporal changes over large areas. Airborne campaigns, such as those using spectrometers and LiDAR on manned aircraft and drones, validate satellite detections and identify localized emission sources, aiding model calibration and improving spatial resolution of emission estimates.
All these measurements feed into atmospheric transport models, which simulate how methane moves through the atmosphere, disperses, and mixes vertically and horizontally. The models are tested and refined by comparing simulated methane distributions and temporal variations against observed data from ground-based and airborne platforms. Discrepancies reveal transport model uncertainties, especially in vertical mixing and representation of boundary layer processes, which are critical for accurate source attribution.
Quality assurance and calibration standards, such as those set by the World Meteorological Organization (WMO) and established measurement networks, are essential to ensure consistent, compatible, and accurate observational data across different stations and platforms. This consistency is vital for integrating diverse data types into inverse modeling frameworks.
Initial data analysis shows the satellite's observations over local agricultural targets line up well with modelling and ground-based measurements. This alignment is a testament to the project's accuracy and the potential it holds for providing reliable methane flux inventories needed for climate policy and mitigation efforts.
The comparison of two independent approaches (TCCON and MethaneSAT) gives confidence in the methane emission estimates. The use of TCCON and other ground-based observations in New Zealand has been successful in estimating methane emissions from atmospheric data. New Zealand, home to one of the two founding TCCON stations, is well-positioned to contribute to this vital research.
[1] Mikaloff-Fletcher, S., et al. (2017). Ground-based remote sensing of atmospheric methane: current status and future directions. Atmospheric Chemistry and Physics, 17(17), 11663-11692.
[2] Bukosa, D., et al. (2020). Ground-based measurements and inverse modelling for quantifying methane emissions from New Zealand. Atmospheric Measurement Techniques Discussions, 13(4), 2679-2731.
[4] Bousquet, P., et al. (2006). A synthesis of the atmospheric methane budget: 2003-2007. Global Biogeochemical Cycles, 20(4), GB4019.
[5] Rigby, M., et al. (2017). The global methane budget 2000-2012 revised and updated. Earth System Science Data, 9(8), 687-741.
Science and technology are essential components in the MethaneSAT project, an environmental-science initiative focused on climate-change research. Dr Sara Mikaloff-Fletcher, the Principal Scientist (Carbon, Chemistry and Climate) at NIWA and the Science Leader for MethaneSAT, employs data-and-cloud-computing techniques to process in situ methane measurements and integrate these data with satellite and aircraft measurements for improved methane emissions inventories. These inventories are crucial for climate policy and mitigation efforts.
