Abstract
<jats:p>Abstract. Many cities have an interest in understanding and mitigating their greenhouse gas emissions. Impressive progress has been made in gridded carbon dioxide emission products, but there is still significant uncertainty in urban methane sources and their magnitudes. There have been several recent works that built regional gridded methane estimates using a variety of methods. Typically, these are built to update the existing products with more recent data/methods or for higher resolution data as it allows measurement-based analyses to better adjust emissions estimates, given the complex, heterogeneous mix of sources in urban areas. This paper introduces the Modular Methane Mapping Tool (M3T) to support these efforts. M3T is a tool that can generate an ensemble of gridded methane emissions inventories focused primarily on sectors relevant to urban emissions using research-based methods. The tool is focused on urban areas as existing inventories suggest they represent approximately 10 % of all anthropogenic methane emissions across Continental United States (CONUS) and cities often have the autonomy to affect their emissions through legislation. M3T can generate inventories at any resolution that is 0.01 degrees (~1 km) or coarser for any area within the CONUS, and any year after 2011 using publicly available data. We compare 2019 output to the existing Environmental Protection Agency product for select urban areas, including the largest emitter of the New York urban area. Average emissions across M3T ensemble members are low relative to measurement studies, though the thermogenic fraction is in line with studies using ethane. While some ensemble members have methane emissions that are more consistent with measurement studies, these members have much lower thermogenic fractions. This highlights that there are still unaccounted for or underestimated biogenic and thermogenic sources. M3T is meant to support research efforts to better understand methane emissions as it allows multiple bottom-up methods and emission factors to be easily compared against measurements. Ideally, the tool will also expand as new research is conducted.</jats:p>