AGES+ Coordinating Activities

Aircraft: NCAR/NSF C-130

Greater New York Oxidant Trace gas Halogen and Aerosol Airborne Mission (GOTHAAM)

Science Objectives

NYMA map — GOTHAAM will probe atmospheric chemistry in the diverse chemical environments (biogenic, urban, marine) found in the New York Metropolitan Area. The inset is a wind rose showing the origin of surface winds in the summertime. Southerly flow is most common, followed by southwesterly and northeasterly.

The New York Metropolitan Area (NYMA) is home to more than 20 million people and experiences high levels of pollution. In the summer of 2021, 7 of 11 monitoring stations in the NYMA reported ozone levels in exceedance of the EPA National Ambient Air Quality Standard (last accessed 2022 June 2). Total PM_2.5 loading has improved significantly in recent decades due to air quality regulations, but a growing contribution of organic matter to the total aerosol burden may have implications for particle toxicity and regulatory policy. Encompassing rural, urban, and marine environments, the NYMA is subject to a complex mixture of emissions, chemistry, and coastal meteorology that ultimately determine the production and fate of harmful pollutants.

The Greater New York Oxidant Trace Gas Halogen and Aerosol Airborne Mission (GOTHAAM) is an NSF-funded investigation of the detailed chemical processes controlling atmospheric composition in the NYMA. State-of-the-art in situ instrumentation will be deployed on the NCAR/NSF C-130 aircraft in July and August – rescheduled to 2025 – to address four related objectives.

Quantify the relative contributions from various volatile organic compound (VOC) sources (biogenic, fossil fuel combustion, consumer products) and how they contribute to chemical reactivity.
Determine the relative potential contribution of each VOC class to secondary organic aerosol (SOA) as the anthropogenic plume evolves.
Quantify the relative importance of oxidation pathways for both gas phase and aerosol species and characterize how processes vary diurnally and between chemical systems (biogenic/urban/marine).
Investigate how nighttime processes influence next-day chemistry and composition.

GOTHAAM observations will improve understanding of formation of O₃ and PM_2.5 pollution in the NYMA. By sharing and disseminating results, GOTHAAM will help air quality agencies in the region and other similar mega cities take action to mitigate harmful pollution.

Proposed Payload

The NCAR/NSF C-130 payload is optimized to address GOTHAAM objectives. Multi-instrument VOC measurements will thoroughly characterize VOC sources and oxidation products in the high and intermediate volatility range (Objectives 1, 2, 3). Direct observations of key oxidants will constrain the lifetime of reactive carbon and nitrogen (Objective 3). Measurements of gas-phase aerosol precursors and aerosol composition will elucidate major pathways leading to secondary pollutants (Objectives 2, 3). Simultaneous observations of halogenated gases, sulfur-containing gases, and aerosol properties will illuminate how the marine atmosphere processes urban outflow (Objectives 3, 4). In combination, the GOTHAAM payload can yield a comprehensive picture of atmospheric chemistry in the NYMA.

Core instrumentation for GOTHAAM

Species Measured	Technique	PI	Institution
OH, HO₂, RO₂, H₂SO₄	NO₃^- CIMS	Lee Mauldin	CU Boulder
oVOCs, halogens, ClNO₂, HONO, N₂O₅, etc	I^- CIMS	Joel Thornton	U Washington
VOCs	PTR-TOF Vocus	Joel Thornton	U Washington
VOCs	Mini WAAS	Eric Apel	NCAR
Organic gases	TOGA-TOF	Eric Apel	NCAR ACOM
HCHO	ISAF	Reem Hannun / Glenn Wolfe	UMD / NASA
NOx, ∑NOy, O₃	Chemiluminescence	Ale Franchin	NCAR ACOM
Speciated PANs	TD-CIMS	Frank Flocke	NCAR ACOM
GHG/CO/SO₂	Picarro	Teresa Campos	NCAR ACOM
Individual particle composition, including sea salt	ATOF-MS	Kerri Pratt	U Michigan
SOA composition	AMS	Delphine Farmer	CSU
Aerosol impaction collector	TRAC	Daniel Knopf	Stony Brook
Aerosol size distributions	UHSAS, cloud probe	n/a	NCAR EOL
J-values	HARP actinic flux	Samuel Hall	NCAR ACOM

All measurements are in situ. Gas-phase observations include speciated VOC, speciated and total reactive nitrogen, radicals (OH, HO₂, RO₂), greenhouse gases, sulfur and halogen-containing compounds, and more. Aerosol measurements include single-particle and bulk chemical composition, physical properties, and size distributions.

Mission Execution

With 150 flight hours, GOTHAAM will generate a high-resolution 4-D portrait of atmospheric composition and processes in the NYMA during the peak ozone season. Flights will include a combination of Lagrangian and Eulerian strategies and focus on the same domain as the NEC-AQ-GHG Cessna research aircraft. Missed approaches at designated airports will provide full vertical profiles of short-lived reactive species and improve connections to ground monitoring networks. Flights will also exploit natural variability in near-surface wind patterns to probe the various chemical regimes both independently and in combination (e.g., urban plume outflow over land vs. over water). Multi-scale models, including F0AM, CMAQ, and GEOS-Chem, will support forecasting and analysis

Anticipated Outcomes

The next-generation instrumentation on GOTHAAM will provide an unprecedented dataset detailing NYMA atmospheric composition. Analyses will reveal the controls on O₃ and PM formation, informing air quality stakeholders in both NY and other megacities. Regional and global models struggle in coastal regions, and GOTHAAM observations can serve as a benchmark constraint for pinpointing model shortfalls and testing new parameterizations. Finally, with potential concurrent sampling under TEMPO, GOTHAAM data will serve as a ground-truth resource for validation of satellite retrievals and applications of satellite data to studies of emissions and chemistry.