Early Results from a Pandora Network in Boston

Jeffrey Geddes, Department of Earth & Environment, Boston University
Contact: jgeddes@bu.edu


Contents:

1. Network Plan and Deployment Status

2. Multi-Season Intercomparison of Pandoras at BU

3. The View from Space and Intra-Urban Differences in NO2 Columns

4. Mesoscale Meteorological Controls on Diurnal NO2 Profiles

5. Impacts of COVID Restrictions on NO2 at the Surface and in the Column

6. Acknowledgements



1. Network Plan and Deployment Status:

5 x Pandora Spectrometers (4 x Geddes; 1 x Chance)
7 x In-situ NO2 (2 x Geddes; 5 x MassDEP)
1 x Aerosol Lidar (1 x Wofsy)
3 x EM27 FT Spectrometers for CH4, CO2, CO (3 x Wofsy)
2 x Meteorology (1 x Geddes; 1 x NOAA-ISD)

Deployment Status: Pandoras Active at BU (since April 2019) and Harvard (since December 2019); Deployment at Blue Hill Next Week; Siting Agreements with MassDEP (Lynn PAMS Site) and Town of Winthrop (Logan Airport)

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2. Multi-Season Intercomparison of Pandoras at BU:

Pandoras 107, 139, 153, 154, and 155 were collocated at Boston University from April to December 2019, in order to explore and quantify across-system precision.

At 10-minute averaging, we find Pandora direct-sun retrievals result in RMSE ~ 0.02-0.03 DU (equivalent to ~0.5-0.8 x 1015 molec/cm2) between instruments, with minimal bias.

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3. The View from Space and Intra-Urban Differences in NO2 Columns

 The Boston University and Harvard sites are located about ~3.0 km apart, frequently within the same TROPOMI pixel. Differences in total column NO2 between these sites frequently exceed a factor of 2, well outside the uncertainty of the instrumental retrieval. We will investigate how these differences depend on time of day, and atmospheric transport.

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4. Mesoscale Meteorological Controls on Diurnal NO2 Profiles

Diurnal profiles of NO2 column density are very sensitive to prevailing meteorological conditions, unlike in-situ NO2 measured at the surface.

Prevailing meteorological conditions at Logan Airport (June-July-August, 2019):

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5. Impacts of COVID Restrictions on NO2 at the Surface and in the Column

At the peak of COVID-related restrictions, MassDOT reported declines in traffic of up to 60-70%. Total column NO2 recorded at Boston University showed declines of 40% compared to the same time last year (with declines in the 95th percentile on the order of 60%). This is consistent with evidence from traffic data and in-situ NO2 measured at the surface. Busy urban intersections saw the steepest declines, while declines at background sites (and even on busy highways) were not at high.

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6. Acknowledgements:

Thanks to Elena Spinei Lind, Taylor J. Adams, and Kelly Chance.
This project is generously supported by grants from NASA, NOAA, and NSF.