Preprints
https://doi.org/10.5194/egusphere-2024-1401
https://doi.org/10.5194/egusphere-2024-1401
22 May 2024
 | 22 May 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Interpreting Summertime Hourly Variation of NO2 Columns with Implications for Geostationary Satellite Applications

Deepangsu Chatterjee, Randall V. Martin, Chi Li, Dandan Zhang, Haihui Zhu, Daven K. Henze, James H. Crawford, Ronald C. Cohen, Lok N. Lamsal, and Alexander M. Cede

Abstract. Accurate representation of the hourly variation of the NO2 column-to-surface relationship is needed to interpret geostationary constellation observations of tropospheric NO2 columns. Prior work has revealed inconsistency in the hourly variation in NO2 columns and surface concentrations. In this study, we use the high-performance configuration of the GEOS-Chem model (GCHP) to interpret the daytime hourly variation in NO2 total columns and surface concentrations during summer. We use summer-time Pandora sun photometers and aircraft measurements during the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) field campaign over Maryland, Texas, and Colorado as well as 50 sites (31: contiguous USA, 10: Europe, 9: Asia) from the Pandonia Global Network (PGN). We correct the Pandora columns for 1) hourly variation in the column effective temperature driven by the fractional boundary layer contribution to the total column, and 2) change in local solar time along the line-of-sight of the Pandora instrument. The corrected Pandora observations are increased by about 5–6 × 1014 molecules cm-2 at 9 AM and 6 PM across all Pandora sites. We conduct fine resolution (~12 km) simulations over the contiguous US, Europe, and East Asia using the stretched grid capability of GCHP. We also examine the effect of planetary boundary layer height (PBLH) corrections on the total columns. We first evaluate the GCHP simulated absolute NO2 concentration with Pandora and aircraft observations. We find that fine resolution simulations at 12 km compared with moderate resolution ~55 km reduce the Normalized Bias (NB) versus Pandora total columns (19 % to 10 %) and versus aircraft measurements (25 % to 13 %) over Maryland, Texas, and Colorado. Fine resolution simulations at 12 km compared with moderate resolution at 55 km reduce the NB versus Pandora total columns over the eastern US (17 % to 9 %), western US (22 % to 14 %), Europe (24 % to 15 %), and Asia (29 % to 21 %). We next use the 12 km simulation to examine the hourly variation in the NO2 column and surface concentrations. We explain the weaker hourly variation in NO2 columns than at the surface as a function of 1) hourly variation in the column effective temperature, 2) hourly variation in the local solar time along the Pandora line-of-sight and 3) the integral of weakly connected layers; with the lowest 500 m exhibiting greater NO2 concentrations in morning and evening than midday, while the residual column above 500 m dominates the total column with weaker variability.

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Deepangsu Chatterjee, Randall V. Martin, Chi Li, Dandan Zhang, Haihui Zhu, Daven K. Henze, James H. Crawford, Ronald C. Cohen, Lok N. Lamsal, and Alexander M. Cede

Status: open (until 03 Jul 2024)

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  • RC1: 'Comment on egusphere-2024-1401', Anonymous Referee #1, 29 May 2024 reply
Deepangsu Chatterjee, Randall V. Martin, Chi Li, Dandan Zhang, Haihui Zhu, Daven K. Henze, James H. Crawford, Ronald C. Cohen, Lok N. Lamsal, and Alexander M. Cede
Deepangsu Chatterjee, Randall V. Martin, Chi Li, Dandan Zhang, Haihui Zhu, Daven K. Henze, James H. Crawford, Ronald C. Cohen, Lok N. Lamsal, and Alexander M. Cede

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Short summary
We investigate the hourly variation of NO2 columns and surface concentrations by applying the GEOS-Chem model to interpret aircraft and ground-based measurements over the US, and Pandora sun photometer measurements over the US, Europe, and Asia. Corrections to the Pandora columns and finer model resolution improve the modeled representation of the summertime hourly variation of total NO2 columns to enable explaining the weaker hourly variation in NO2 columns than at the surface.