Back to Search Start Over

Using portable low-resolution spectrometers to evaluate Total Carbon Column Observing Network (TCCON) biases in North America

Authors :
Nasrin Mostafavi Pak
Jacob K. Hedelius
Sébastien Roche
Liz Cunningham
Bianca Baier
Colm Sweeney
Coleen Roehl
Joshua Laughner
Geoffrey Toon
Paul Wennberg
Harrison Parker
Colin Arrowsmith
Joseph Mendonca
Pierre Fogal
Tyler Wizenberg
Beatriz Herrera
Kimberly Strong
Kaley A. Walker
Felix Vogel
Debra Wunch
Publication Year :
2023

Abstract

EM27/SUN devices are portable solar-viewing Fourier transform spectrometers (FTSs) that are being widely used to constrain measurements of greenhouse gas emissions and validate satellite trace gas measurements. On a 6-week-long campaign in the summer of 2018, four EM27/SUN devices were taken to five Total Carbon Column Observing Network (TCCON) stations in North America, to measure side by side, to better understand their durability, the accuracy and precision of retrievals from their trace gas measurements, and to constrain site-to-site bias among TCCON sites. We developed new EM27/SUN data products using both previous and current versions of the retrieval algorithm (GGG2014 and GGG2020) and used coincident AirCore measurements to tie the gas retrievals to the World Meteorological Organization (WMO) trace gas standard scales. We also derived air-mass-dependent correction factors for the EM27/SUN devices. Pairs of column-averaged dry-air mole fractions (denoted with an X) measured by the EM27/SUN devices remained consistent compared to each other during the entire campaign, with a 10 min averaged precision of 0.3 ppm (parts per million) for XCO2, 1.7 ppb (parts per billion) for XCH4, and 2.5 ppb for XCO. The maximum biases between TCCON stations were reduced in GGG2020 relative to GGG2014 from 1.3 to 0.5 ppm for XCO2 and from 5.4 to 4.3 ppb for XCH4 but increased for XCO from 2.2 to 6.1 ppb. The increased XCO biases in GGG2020 are driven by measurements at sites influenced by urban emissions (Caltech and the Armstrong Flight Research Center) where the priors overestimate surface CO. In addition, in 2020, one EM27/SUN instrument was sent to the Canadian Arctic TCCON station at Eureka, and side-by-side measurements were performed in March–July. In contrast to the other TCCON stations that showed an improvement in the biases with the newer version of GGG, the biases between Eureka's TCCON measurements and those from the EM27/SUN degraded with GGG2020, but this degradation was found to be caused by a temperature dependence in the EM27/SUN oxygen retrievals that is not apparent in the GGG2014 retrievals.

Subjects

Subjects :
Atmospheric Science

Details

Language :
English
ISSN :
18678548
Database :
OpenAIRE
Accession number :
edsair.doi.dedup.....3ca51470028ada3879462077472bf7f2