DOI: 10.5061/dryad.wpzgmsbtk
title: CrIS PANs megacity dataset for São Paulo and Lagos

description: The COVID-19 pandemic perturbed air pollutant emissions as cities shut
 down worldwide. Peroxyacyl nitrates (PANs) are important tracers of
 photochemistry that are formed through the oxidation of non-methane
 volatile organic compounds (NMVOCs) in the presence of nitrogen oxide
 radicals (NOx = NO + NO2). We use satellite measurements of free
 tropospheric PANs from the S-NPP Cross-Track Infrared Sounder (CrIS) over
 eight of the world’s megacities: Mexico City, Beijing, Los Angeles, Tokyo,
 São Paulo, Delhi, Lagos, and Karachi. We quantify the seasonal cycle of
 PANs over these megacities and find seasonal maxima in PANs correspond to
 seasonal peaks in local photochemistry. CrIS is used to explore changes in
 PANs in response to the COVID-19 lockdowns. Statistically significant
 changes to PANs occurred over two megacities: Los Angeles (PAN decreased)
 and Beijing (PAN increased). Our analysis suggests that large
 perturbations in NOx may not result in significant declines in NOx export
 potential of megacities.
description: # CrIS PANs megacity dataset for São Paulo and Lagos
 [https://doi.org/10.5061/dryad.wpzgmsbtk](https://doi.org/10.5061/dryad.wpzgmsbtk) These data files contain all filtered CrIS PANs and CO tropospheric average mixing ratio retrievals over the São Paulo & Lagos urban megacity subregions. **Temporal Coverage of Data:** 2016-01-01 to 2021-05-20 Daily satellite data for the entire megacity area at 13:30 LT. **Spatial extent of data:** **latitude extents São Paulo:** 23.39838°S - 23.689°S **longitude extents São Paulo:** 46.36157°W - 46.80453°W **latitude extents Lagos:** 6.451°N - 6.64°N **longitude extents Lagos:** 3.23°E - 3.41°E Data has been filtered as described in the manuscript. To reproduce figures in submitted manuscript: Figures in the manuscript utilized daily means and monthly means. ## Description of the data and file structure seven columns of data: XPAN\_orig, Correction, XH2O, Lat, Lon, Year, Month, Day, XCO, XPAN. variables are described below. | Variable | Units | Description | | -------- | ----- | ----------- | | XPAN\_orig | parts per billion by volume [ppbv] | XPAN800 value reported in datafile. <br>L2 variable called XPAN800. Tropospheric average of PANs from 800 hPa to the tropopause.<br>Missing data have been filtered out for various reasons. | | Correction | parts per billion by volume [ppbv] | Correction value to be added to XPAN\_orig as described in Payne et al., 2022 | | XH2O | molecules/m2 | Reported total column water vapor value from L2 water valor files. Correction value uses this.<br>Correction formula has been applied in XPAN variable (below). | | Lat | degrees | Latitude <br>Max São Paulo: 23.39838<br>Min São Paulo: -23.689<br>Max Lagos: 6.64<br>Min Lagos: 6.451 | | Lon | degrees | Longitude<br>Max São Paulo: -46.36157<br>Min São Paulo: -46.80453<br>Max Lagos: 3.41<br>Min Lagos: 3.23 | | Year | Year | Format: YYYY<br>Max: 2021<br>Min: 2016 | | Month | Month | Format: MM | | Day | Day | Format: DD | | XCO | parts per billion by volume [ppbv] | Tropospheric average created using the L2 variable called “Species”. From 825 hPa - 215 hPa.<br>Missing data have been filtered out. | | XPAN | parts per billion by volume [ppbv] | Corrected XPAN value. This is the XPAN value to use going forward. | ## Sharing/Access information **Other Megacity datasets:** Kevin W. Bowman (2023), TROPESS CrIS-SNPP L2 for Beijing Megacity, Summary Product V1, Greenbelt, MD, USA, Goddard Earth Sciences Data and Information Services Center (GES DISC), Accessed: **[*August 2022*]**, [10.5067/GBMBES47TUOI](https://doi.org/10.5067/GBMBES47TUOI) Mexico City, Tokyo, Karachi, Delhi, and Los Angeles are also available on the NASA GES DISC. **Uncertainty, precision, and accuracy of measurements** CrIS PAN algorithm description and further information can be found in: Payne, Vivienne H., Kulawik, S. S., Fischer, E. V., Brewer, J. F., Huey, L. G., Miyazaki, K., Worden, J. R., Bowman, K. W., Hintsa, E. J., Moore, F., Elkins, J. W., & Juncosa Calahorrano, J. (2022). Satellite measurements of peroxyacetyl nitrate from the Cross-Track Infrared Sounder: comparison with ATom aircraft measurements. Atmospheric Measurement Techniques, 15(11), 3497–3511. https://doi.org/10.5194/amt-15-3497-2022 <br> **Additional references:** Bowman, K. W., Rodgers, C. D., Kulawik, S. S., Worden, J., Sarkissian, E., Osterman, G., Steck, T., Lou, M., Eldering, A., Shephard, M., Worden, H., Lampel, M., Clough, S., Brown, P., Rinsland, C., Gunson, M., and Beer, R.: Tropospheric Emission Spectrometer: Retrieval method and error analysis. IEEE Trans. on Geosci. Remote Sensing, 44(5), 2006. Fu, D., Kulawik, S. S., Miyazaki, K., Bowman, K. W., Worden, J. R., Eldering, A., Livesey, N. J., Teixeira, J., Irion, F. W., Herman, R. L., Osterman, G. B., Liu, X., Levelt, P. F., Thompson, A. M. and Luo, M.: Retrievals of tropospheric ozone profiles from the synergism of AIRS and OMI: methodology and validation, Atmos. Meas. Tech., 11(10), 5587–5605, doi:10.5194/amt-11-5587- 2018-supplement, 2018. Worden, J., Kulawik, S., Frankenberg, C., Payne, V., Bowman, K., Cady-Pereira, K., Wecht, K., Lee, J.-E. and Noone, D.: Profiles of CH4, HDO, H2O, and N2O with improved lower tropospheric vertical resolution from Aura TES radiances, Atmos. Meas. Tech., 5(2), 397–411, doi:10.5194/amt-5-397-2012, 2012.