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Assessing the Impact of Corona-Virus-19 on Nitrogen Dioxide Levels over Southern Ontario, Canada. REMOTE SENSING 2020. [DOI: 10.3390/rs12244112] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A lockdown was implemented in Canada mid-March 2020 to limit the spread of COVID-19. In the wake of this lockdown, declines in nitrogen dioxide (NO2) were observed from the TROPOspheric Monitoring Instrument (TROPOMI). A method is presented to quantify how much of this decrease is due to the lockdown itself as opposed to variability in meteorology and satellite sampling. The operational air quality forecast model, GEM-MACH (Global Environmental Multi-scale - Modelling Air quality and CHemistry), was used together with TROPOMI to determine expected NO2 columns that represents what TROPOMI would have observed for a non-COVID scenario. Applying this methodology to southern Ontario, decreases in NO2 emissions due to the lockdown were seen, with an average 40% (roughly 10 kt[NO2]/yr) in Toronto and Mississauga and even larger declines in the city center. Natural and satellite sampling variability accounted for as much as 20–30%, which demonstrates the importance of taking meteorology into account. A model run with reduced emissions (from 65 kt[NO2]/yr to 40 kt[NO2]/yr in the Greater Toronto Area) based on emission activity data during the lockdown period was found to be consistent with TROPOMI NO2 columns.
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A Long-Term Passive Microwave Snowoff Record for the Alaska Region 1988–2016. REMOTE SENSING 2020. [DOI: 10.3390/rs12010153] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Snowoff (SO) date—defined as the last day of observed seasonal snow cover—is an important governor of ecologic and hydrologic processes across Alaska and Arctic-Boreal landscapes; however, our understanding and capacity for the monitoring of spatial and temporal variability in the SO date is still lacking. In this study, we present a 6.25 km spatially gridded passive microwave (PMW) SO data record, complimenting current Alaskan SO records from Moderate Resolution Imaging Spectrometer (MODIS) and Landsat, but extending the SO record an additional 13 years. The PMW SO record was validated against in situ snow depth observations and showed favorable accuracy (0.66–0.92 mean correlations; 2–10 day mean absolute errors) for the major climate regions of Alaska. The PMW SO results were also within 10 days of finer spatial scale SO observational records, including Interactive Multisensor Snow and Ice Mapping System (IMS), MODIS, and Landsat, for a majority (75%) of Alaska. However, the PMW record showed a general SO delay at higher elevations and across the Alaska North Slope, and earlier SO in the Alaska interior and southwest regions relative to the other SO records. Overall, we assign an uncertainty +/−11 days to the PMW SO. The PMW SO record benefits from the near-daily temporal fidelity of underlying brightness temperature (Tb) observations and reveals a mean regional trend in earlier SO timing (−0.39 days yr−1), while significant (p < 0.1) SO trend areas encompassed 11% of the Alaska domain and ranged from −0.11 days yr−1 to −1.31 days yr−1 over the 29-year satellite record. The observed SO dates also showed anomalous early SO dates during markedly warm years. Our results clarify the pattern and rate of SO changes across Alaska, which are interactive with global warming and contributing to widespread permafrost degradation, changes in regional hydrology, ecosystems, and associated services. Our results also provide a robust means for SO monitoring from satellite PMW observations with similar precision as more traditional and finer scale observations.
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Griffin D, McLinden CA, Boersma F, Bourassa A, Dammers E, Degenstein D, Eskes H, Fehr L, Fioletov V, Hayden K, Kharol SK, Li SM, Makar P, Martin RV, Mihele C, Mittermeier RL, Krotkov N, Sneep M, Lamsal LN, Ter Linden M, van Geffen J, Veefkind P, Wolde M, Zhao X. High resolution mapping of nitrogen dioxide with TROPOMI: First results and validation over the Canadian oil sands. GEOPHYSICAL RESEARCH LETTERS 2019; 46:1049-1060. [PMID: 33867596 PMCID: PMC8051066 DOI: 10.1029/2018gl081095] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Accepted: 12/22/2018] [Indexed: 05/20/2023]
Abstract
UNLABELLED TROPOMI, on-board the Sentinel-5 Precursor satellite is a nadir-viewing spectrometer measuring reflected sunlight in the ultraviolet, visible, near-infrared, and shortwave infrared spectral range. From these spectra several important air quality and climate-related atmospheric constituents are retrieved at an unprecedented high spatial resolution, including nitrogen dioxide (NO2). We present the first retrievals of TROPOMI NO2 over the Canadian Oil Sands, contrasting them with observations from the OMI satellite instrument, and demonstrate its ability to resolve individual plumes and highlight its potential for deriving emissions from individual mining facilities. Further, the first TROPOMI NO2 validation is presented, consisting of aircraft and surface in-situ NO2 observations, as well as ground-based remote-sensing measurements between March and May 2018. Our comparisons show that the TROPOMI NO2 vertical column densities are highly correlated with the aircraft and surface in-situ NO2 observations, and the ground-based remote-sensing measurements with a low bias (15-30 %) over the Canadian Oil Sands. PLAIN LANGUAGE SUMMARY Nitrogen dioxide (NO2) is a pollutant that is linked to respiratory health issues and has negative environmental impacts such as soil and water acidification. Near the surface the most significant sources of NO2 are fossil fuel combustion and biomass burning. With a recently launched satellite instrument (TROPOspheric Monitoring Instrument; TROPOMI) NO2 can be measured with an unprecedented combination of accuracy, spatial coverage, and resolution. This work presents the first TROPOMI NO2 measurements near the Canadian Oil Sands and shows that these measurements have an outstanding ability to detect NO2 on a very high horizontal resolution that is unprecedented for satellite NO2 observations. Further, these satellite measurements are in excellent agreement with aircraft and ground-based measurements.
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Affiliation(s)
- Debora Griffin
- Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario, Canada
| | - Chris A McLinden
- Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario, Canada
| | - Folkert Boersma
- Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands
- Wageningen University, Environmental Sciences Group, Wageningen, The Netherlands
| | - Adam Bourassa
- Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Enrico Dammers
- Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario, Canada
| | - Doug Degenstein
- Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Henk Eskes
- Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands
| | - Lukas Fehr
- Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Vitali Fioletov
- Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario, Canada
| | - Katherine Hayden
- Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario, Canada
| | - Shailesh K Kharol
- Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario, Canada
| | - Shao-Meng Li
- Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario, Canada
| | - Paul Makar
- Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario, Canada
| | - Randall V Martin
- Dalhousie University, Department of Physics and Atmospheric Science, Halifax, Nova Scotia, Canada
| | - Cristian Mihele
- Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario, Canada
| | - Richard L Mittermeier
- Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario, Canada
| | - Nickolay Krotkov
- Laboratory for atmospheric chemistry and dynamics, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - Maarten Sneep
- Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands
| | - Lok N Lamsal
- Laboratory for atmospheric chemistry and dynamics, NASA Goddard Space Flight Center, Greenbelt, MD, USA
- Goddard Earth Sciences Technology and Research, Universities Space Research Association, Columbia, MD, USA
| | - Mark Ter Linden
- Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands
- Science and Technology (S&T), Delft, Netherlands
| | - Jos van Geffen
- Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands
| | - Pepijn Veefkind
- Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands
- Delft University of Technology, Delft, The Netherlands
| | - Mengistu Wolde
- National Research Council Canada, Flight Research Laboratory, Ottawa, K1A 0R6, Canada
| | - Xiaoyi Zhao
- Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario, Canada
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