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GReenhouse gas And Air Pollutants Emissions System (GRA2PES)

Objective

Developing a joint activity between NOAA Chemical Science Laboratory (NOAA CSL) and NIST's 

Greenhouse Gas (GHG) Measurement Program is consistent with the missions of both NOAA 

and NIST. This activity will enhance the Department of Commerce's capability to model and 

map greenhouse gas and air pollutant emissions and their associated uncertainties. These 

approaches use, for example, activity-based data, socio-economic data, and energy statistics 

along with emission factors – commonly referred to as "bottom-up" GHG emission estimation. 

At present, the estimation of GHG emissions and air pollutants are largely independent 

exercises but their inter-dependence, especially at urban scales, are increasingly gaining 

attention. For example, there are potential co-benefits from reducing GHGs that improve air 

quality while mitigating climate impacts.

The joint activity will enhance the development of authoritative referenced "bottom-up" 

emission data and uncertainty evaluation at spatial and temporal resolutions relevant to both 

improving air quality (AQ) and mitigating greenhouse gas (GHG) emissions including city, State, 

and regional scales. Such spatial and temporal mapping enables data assimilation systems or 

"top-down" methods, such as those that combine atmospheric observations (e.g., surface, 

aircraft, satellite) and meteorological models, to better constrain emission estimates. This 

information will have low latency and be publicly available at disaggregate spatial and temporal 

resolutions. Systems can be developed for nowcasting, forecasting, or hindcasting. Uncertainty 

methodologies will be developed giving capabilities to map regions where improvements to 

data and models will be most beneficial and include estimation and novel combinations of 

different emission information. It is anticipated that statistical analysis methods developed for 

pollutant emissions will transfer, to a large degree, to GHG emissions.

Future work will include data assimilation of observations from multiple platforms and various 

species to estimate emissions. This may include ground based in-situ measurement, remote 

sensing, etc. Such a system will be able to ingest multi-species data from satellite constellations 
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like NOAA's Geostationary Extended Observations (GeoXO) in the future, and potentially GHGs 

if they are included within the mission. Assimilation of multiple data will help evaluate satellite 

retrievals while improving the quantification of flux estimates.

Organizational Structure

The GReenhouse gas And Air Pollutants Emissions System (GRA2PES) initiative is a joint activity 

managed by both NIST's Greenhouse Gas (GHG) Measurement Program and NOAA Chemical 

Science Laboratory (CSL). A core group of scientists and practitioners from each organization 

will discuss objectives, challenges, preliminary work on a regular basis (e.g., quarterly), 

culminating in a yearly activity review involving Directors from both programs and other 

interested parties from government, academia, and the private sector. Annual meetings will 

also incorporate a planning component to better shape future directions and promote 

engagement with the stakeholder community. The core group of scientists will produce and 

revise yearly goals and future objectives within a planning documentation.

Current Capabilities

NOAA Chemical Science Laboratory (CSL)

At present, NOAA CSL performs emissions and chemical transport modeling to support 

development of NOAA's weather-chemistry models, and provide timely emissions information 

to stakeholder groups (e.g., State and local air quality agencies, U.S. EPA, and industry). This 

research is largely performed in-house by NOAA CSL scientists and affiliates for the Cooperative 

Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder. 

At present, NOAA CSL does not perform extensive GHG modeling and seeks to partner with the 

NIST GHG Measurement Program to create an emission modeling system that fully integrates 

greenhouse gas and air quality species.

NOAA modeling personnel include:

• Brian McDonald, NOAA emissions and air quality modeling lead – will provide guidance

• Meng Li, NOAA affiliate – will provide guidance on merging air quality and GHG bottomup emission inventories

• Colin Harkins, NOAA affiliate – primary person responsible for software development of 

emissions modeling at NOAA

• Congmeng (Trammell) Lyu, NOAA affiliate – primary person responsible for evaluating 

emissions modeling at NOAA with atmospheric observations

NIST Greenhouse Gas (GHG) Measurement Program 

To date, NIST funds academic research on modeling of GHG emissions and has an active 

atmospheric observation and modeling research program. Several peer-reviewed articles have 

demonstrated that NIST-funded research has created the base knowledge for modeling GHG 
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emissions that can be used/evaluated with atmospheric observations. The NIST GHG 

Measurement Program intends to expand aspects of the academically funded research into the 

NIST Program with an emphasis on development of uncertainty analyses of these relatively 

complex models. At present, the NIST Program does not have emission modeling expertise, but 

it's Statistical Engineering Division has extensive knowledge and expertise in analyzing 

measurement systems to develop methodologies for estimating their uncertainties.

NIST statistical personnel include:

• Antonio Possolo, NIST Chief Statistician and expert in uncertainty methods – will provide 

guidance

• Jack Prothero, NIST statistician – primary person responsible for emission modeling at 

NIST

• Mikela Waldman, NIST associate – engaged in emission modelling at NIST

Tangential Work

At present, NOAA Air Resources Laboratory (ARL) is developing a near real-time (NRT) data 

assimilation system using NIST / NOAA Global Monitoring Laboratory (GML) in-situ observations 

and resources developed in NOAA GML and NOAA ARL. The inventory developed as part of the 

GRA2PES initiative will be used within this system. It is assumed that both GRA2PES and the NRT 

data assimilation system will converge within 5 to 10 years once both projects reach more 

maturity.

In the meantime, NOAA CSL continues to use satellite data and aircraft measurements to 

estimate fluxes for the purposes of evaluating inventories including criteria pollutants and 

methane. This includes data from recent and future flight campaigns as well current and 

upcoming satellite missions.

Workflow

Year 1 - Migrate/transfer emission modeling capabilities in consultation with academic 

researchers to establish a NIST program and coordinate it between NIST and NOAA CSL to 

include liaison with academic researchers in the field where appropriate. Specific tasks may 

include:

• Porting of some academic methods (e.g., Vulcan/Hestia methods, data sources, and 

perhaps code) for NIST usage. Code developed by NIST and NOAA CSL in this research 

effort will eventually be placed in the public domain.

• NIST personnel will learn and use NOAA CSL emissions modeling framework for 

pollutants and develop additional capability migrated from academic (or any other GHG 

method) sources.

• NOAA CSL emission modelers will work with NIST staff to develop/adapt uncertainty 

approaches that can be applied to non-GHG emission estimates.
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• Identify a specific sector/problem to begin as a test-case relevant to both NOAA CSL and 

NIST.

• Compile and review literature.

• Identifying and collate key datasets.

• Given the significant rise in interest in these methods by non-governmental interests 

and in consultation with CSL, NIST will utilize its private sector relationships to work 

toward improving understanding of the boundary between governmental and nongovernmental activities for this activity.

To accomplish task and overall objectives, NIST personnel will travel to NOAA CSL (Boulder) to 

work with CSL emission modelers. In addition, NIST personnel will work with Northern Arizona 

University (NAU) academic researchers, and others as the opportunity arises, to learn and 

transition elements to GRA2PES codebase with the purpose of generating a fully integrated GHG 

and AQ emissions modeling system. The code base will be made transparent, publicly available, 

and held in a repository (e.g., GitHub) allowing for version control. This will likely happen in 

Year 2 or 3.

After Year 1, the joint activity will be assessed by both NIST and NOAA CSL to determine future 

activities, etc. Such future activities could include evaluating the jointly developed emissions 

modeling system with atmospheric observations from the NIST Urban Test Bed program, NOAA 

CSL field campaigns (e.g., AEROMMA, SUNVEx, LISTOS), and satellite data, as well as data 

assimilation of atmospheric observations for improving emission inventories.

Given that GRA2PES is at a nascent stage, NIST and NOAA CSL plan on convening a workgroup in 

early 2023 to entrain other agencies (e.g., NASA, EPA, DOE) into the program to help shape its 

future and scope.