Validation of the Sentinel-5 Precursor TROPOMI cloud data with Cloudnet, Aura OMI O&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;-O&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;, MODIS and Suomi-NPP VIIRS

Compernolle, Steven; Argyrouli, Athina; Lutz, Ronny; Sneep, Maarten; Lambert, Jean-Christopher; Fjæraa, Ann Mari; Hubert, D.; Keppens, Arno; Loyola, Diego; O’Connor, Ewan; Romahn, Fabian; Stammes, P.; Verhoelst, Tijl; Wang, Ping

doi:10.5194/amt-2020-122

Cited by 11 publications

(24 citation statements)

References 19 publications

(33 reference statements)

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“…In the urban site, the average is performed on the pixels including the surface monitoring stations probably explained with the inhomogeneous atmosphere within the pixels which makes the NO 2 VCD a combination of high (urban traffic station) and medium (urban background station) levels not always represented in the surface monitoring station network. Furthermore, the underestimation of the tropospheric satellite NO 2 VCD in urban site could be related to the cloud properties included in the models which are used for the TROPOMI products retrieval as described in Compernolle et al (2020) and Verhoelst et al (2020). As supposed in Ialongo et al (2020) to explain the overestimation of total TROPOMI VCD with respect to ground-based remotely sensed ones retrieved in low-level NO 2 condition, the improvement of the NO 2 products could be reached by replacing the surface reflectance climatology defined by OMI database (Kleipool et al 2008).…”

Section: Tropomi Tropospheric No 2 Vcdmentioning

confidence: 99%

Nitrogen dioxide reductions from satellite and surface observations during COVID-19 mitigation in Rome (Italy)

Bassani

Vichi

Esposito

et al. 2021

Environ Sci Pollut Res

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Lockdown restrictions were implemented in Italy from 10 March 2020 to contain the COVID-19 pandemic. Our study aims to evaluate air pollution changes, with focus on nitrogen dioxide (NO2), before and during the lockdown in Rome and in the surroundings. Significant NO2 declines were observed during the COVID-19 pandemic with reductions of − 50%, − 34%, and − 20% at urban traffic, urban background, and rural background stations, respectively. Tropospheric NO2 vertical column density (VCD) from the TROPOspheric Monitoring Instrument (TROPOMI) was used to evaluate the spatial-temporal variations of the NO2 before and during the lockdown for the entire area where the surface stations are located. The evaluation is concerned with the pixels including one or more air quality stations to explore the capability of the unprecedented high spatial resolution to monitor urban and rural sites from space with relation to the surface measurements. Good agreement between surface concentration and TROPOMI VCD was obtained in Rome (R = 0.64 in 2019, R = 0.77 in 2020) and in rural sites (R = 0.71 in 2019). Inversely, a slight correlation (R = 0.20) was observed in rural areas during the lockdown due to very low levels of NO2. Finally, the TROPOMI VCD showed a sharp decline in NO2, larger in urban (− 43%) than in rural sites (− 17%) as retrieved with the concurrent surface measurements averaging all the traffic and urban background (− 44%) and all the rural background stations (− 20%). These results suggest air pollution improvement in Rome gained from implementing lockdown restrictions.

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Section: Tropomi Tropospheric No 2 Vcdmentioning

confidence: 99%

Nitrogen dioxide reductions from satellite and surface observations during COVID-19 mitigation in Rome (Italy)

Bassani

Vichi

Esposito

et al. 2021

Environ Sci Pollut Res

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“…The upper panel of Figure 3 compares to February 2020. Our higher values compared to Verhoelst et al (2020) is because of the 10% downscaling we apply to Pandora total columns. The difference in sampling footprints of space-and ground-based instruments can influence agreement between the two (Pinardi et al, 2020).…”

Section: Evaluation Of Tropomi With Ground-based Instruments At High-mentioning

confidence: 95%

“…induces a positive bias in the total columns estimated by Verhoelst et al (2020) to be ~10% that we address by downscaling the Pandora total columns and associated errors by 10%. No correction is applied to the tropospheric columns, due to variable contribution of the troposphere to the total column.…”

Section: Evaluation Of Tropomi With Ground-based Instruments At High-mentioning

confidence: 97%

“…The underestimate in TROPOMI stratospheric column variance may contribute to the general pattern in validation studies comparing TROPOMI and Pandora total columns that find TROPOMI is less than Pandora when NO2 is large and more than Pandora when NO2 is small for the global Pandora network (Pinardi et al, 2020;Verhoelst et al, 2020) and at individual Pandora sites. TROPOMI is less than Pandora (-24 to -28%) at a relatively polluted Greater Toronto Area site, but more than Pandora (8-11%) at a cleaner rural site north of the city (X.…”

Section: Evaluation Of Tropomi With Ground-based Instruments At High-mentioning

confidence: 99%

“…The 18% higher TROPOMI than Pandora total columns at Mauna Loa is larger than and opposite in sign to the <10% (-2 ´ 10 14 molecules cm -2 ) meridional difference in TROPOMI stratospheric columns from the near-real time (NRTI) NO2 product and those obtained with twilight measurements from the near-global Système d'Analyse par Observation Zénitale (SAOZ) network of Zenith Scattered Light Differential Optical Absorption Spectroscopy (ZSL-DOAS) instruments (Lambert et al, 2019). The implied difference between SAOZ and Pandora stratospheric columns coincident with TROPOMI (Pandora < SAOZ) may be due to the need to account for time differences between the SAOZ measurements (twilight) and TROPOMI (midday) (Verhoelst et al, 2020).…”

Section: Evaluation Of Tropomi With Ground-based Instruments At High-mentioning

confidence: 99%

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New Observations of Upper Tropospheric NO<sub>2</sub> from TROPOMI

Marais¹,

Roberts²,

Ryan³

et al. 2020

Preprint

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Abstract. Nitrogen oxides (NOx ≡ NO + NO2) in the NOx-limited upper troposphere (UT) are long-lived and so have a large influence on the oxidizing capacity of the troposphere and formation of the greenhouse gas ozone. Models misrepresent NOx in the UT and observations to address deficiencies in models are sparse. Here we obtain a year of near-global seasonal mean mixing ratios of NO2 in the UT (450–180 hPa) at 1 ° x 1° by applying cloud-slicing to partial columns of NO2 from TROPOMI. This follows refinement of the cloud-slicing algorithm with synthetic partial columns from the GEOS-Chem chemical transport model. We find that synthetic cloud-sliced UT NO2 are spatially consistent (R = 0.64) with UT NO2 calculated across the same cloud pressure range and scenes as are cloud-sliced (“true” UT NO2), but the cloud-sliced UT NO2 is 11–22 % more than the "true" all-sky seasonal mean. The largest contributors to differences between synthetic cloud-sliced and “true” UT NO2 are target resolution of the cloud-sliced product and uniformity of overlying stratospheric NO2. TROPOMI, prior to cloud-slicing, is corrected for a 13 % underestimate in stratospheric NO2 variance and a 50 % overestimate in free tropospheric NO2 determined by comparison to Pandora total columns at high-altitude sites in Mauna Loa, Izaña and Altzomoni, and MAX-DOAS and Pandora tropospheric columns at Izaña. Two cloud-sliced seasonal mean UT NO2 products for June 2019 to May 2020 are retrieved from corrected TROPOMI total columns using distinct TROPOMI cloud products that assume clouds are reflective boundaries (FRESCO-S) or water droplet layers (ROCINN-CAL). TROPOMI UT NO2 typically ranges from 20-30 pptv over remote oceans to > 80 pptv over locations with intense seasonal lightning. Spatial coverage is mostly in the tropics and subtropics with FRESCO-S and extends to the midlatitudes and polar regions with ROCINN-CAL, due to its greater abundance of optically thick clouds and wider cloud top altitude range. TROPOMI UT NO2 seasonal means are spatially consistent (R = 0.6–0.8) with an existing coarser spatial resolution (5° latitude x 8° longitude) UT NO2 product from the Ozone Monitoring Instrument (OMI). UT NO2 from TROPOMI is 12–26 pptv more than that from OMI due to increase in NO2 with altitude from the OMI pressure ceiling (280 hPa) to that for TROPOMI (180 hPa), but possibly also systematic altitude differences between the TROPOMI and OMI cloud products. The TROPOMI UT NO2 product offers potential to evaluate and improve representation of UT NOx in models and supplement aircraft observations that are sporadic and susceptible to large biases in the UT.

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New Challenges in Air Quality Measurements

Karagulian

2023

Air Quality Networks

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Validation of the Sentinel-5 Precursor TROPOMI cloud data with Cloudnet, Aura OMI O<sub>2</sub>-O<sub>2</sub>, MODIS and Suomi-NPP VIIRS

Cited by 11 publications

References 19 publications

Nitrogen dioxide reductions from satellite and surface observations during COVID-19 mitigation in Rome (Italy)

Nitrogen dioxide reductions from satellite and surface observations during COVID-19 mitigation in Rome (Italy)

New Observations of Upper Tropospheric NO<sub>2</sub> from TROPOMI

New Challenges in Air Quality Measurements

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Validation of the Sentinel-5 Precursor TROPOMI cloud data with Cloudnet, Aura OMI O&lt;sub&gt;2&lt;/sub&gt;-O&lt;sub&gt;2&lt;/sub&gt;, MODIS and Suomi-NPP VIIRS

Cited by 11 publications

References 19 publications

Nitrogen dioxide reductions from satellite and surface observations during COVID-19 mitigation in Rome (Italy)

Nitrogen dioxide reductions from satellite and surface observations during COVID-19 mitigation in Rome (Italy)

New Observations of Upper Tropospheric NO&lt;sub&gt;2&lt;/sub&gt; from TROPOMI

New Challenges in Air Quality Measurements

Contact Info

Product

Resources

About

Validation of the Sentinel-5 Precursor TROPOMI cloud data with Cloudnet, Aura OMI O<sub>2</sub>-O<sub>2</sub>, MODIS and Suomi-NPP VIIRS

New Observations of Upper Tropospheric NO<sub>2</sub> from TROPOMI