Browsing by Author "Abuhassan, Nader K."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Effects of local meteorology and aerosols on ozone and nitrogen dioxide retrievals from OMI and pandora spectrometers in Maryland, USA during DISCOVER-AQ 2011(Springer Nature, 2013-04-19) Reed, Andra J.; Thompson, Anne M.; Kollonige, Debra E.; Martins, Douglas K.; Tzortziou, Maria A.; Herman, Jay; Berkoff, Timothy A.; Abuhassan, Nader K.; Cede, AlexanderAn analysis is presented for both ground- and satellite-based retrievals of total column ozone and nitrogen dioxide levels from the Washington, D.C., and Baltimore, Maryland, metropolitan area during the NASA-sponsored July 2011 campaign of Deriving Information on Surface COnditions from Column and VERtically Resolved Observations Relevant to Air Quality (DISCOVER-AQ). Satellite retrievals of total column ozone and nitrogen dioxide from the Ozone Monitoring Instrument (OMI) on the Aura satellite are used, while Pandora spectrometers provide total column ozone and nitrogen dioxide amounts from the ground. We found that OMI and Pandora agree well (residuals within ±25 % for nitrogen dioxide, and ±4.5 % for ozone) for a majority of coincident observations during July 2011. Comparisons with surface nitrogen dioxide from a Teledyne API 200 EU NOx Analyzer showed nitrogen dioxide diurnal variability that was consistent with measurements by Pandora. However, the wide OMI field of view, clouds, and aerosols affected retrievals on certain days, resulting in differences between Pandora and OMI of up to ±65 % for total column nitrogen dioxide, and ±23 % for total column ozone. As expected, significant cloud cover (cloud fraction >0.2) was the most important parameter affecting comparisons of ozone retrievals; however, small, passing cumulus clouds that do not coincide with a high (>0.2) cloud fraction, or low aerosol layers which cause significant backscatter near the ground affected the comparisons of total column nitrogen dioxide retrievals. Our results will impact post-processing satellite retrieval algorithms and quality control procedures.Item Regional Characteristics of NO₂ Column Densities from Pandora Observations during the MAPS-Seoul Campaign(Aerosol and Air Quality Research, 2018-09) Chong, Heesung; Lee, Hana; Koo, Ja-Ho; Kim, Jhoon; Jeong, Ukkyo; Kim, Woogyung; Kim, Sang-Woo; Herman, Jay; Abuhassan, Nader K.; Ahn, Junyoung; Park, Jeong-Hoo; Kim, Sang-Kyun; Moon, Kyung-Jung; Choi, Won-Jun; Park, Sang SeoVertical column density (VCD) of nitrogen dioxide (NO₂) was measured using Pandora spectrometers at six sites on the Korean Peninsula during the Megacity Air Pollution Studies-Seoul (MAPS-Seoul) campaign from May to June 2015. To estimate the tropospheric NO₂ VCD, the stratospheric NO₂ VCD from the Ozone Monitoring Instrument (OMI) was subtracted from the total NO₂ VCD from Pandora. European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis wind data was used to analyze variations in tropospheric NO₂ VCD caused by wind patterns at each site. The Yonsei/SEO site was found to have the largest tropospheric NO₂ VCD (1.49 DU on average) from a statistical analysis of hourly tropospheric NO₂ VCD measurements. At rural sites, remarkably low NO₂ VCDs were observed. However, a wind field analysis showed that trans-boundary transport and emissions from domestic sources lead to an increase in tropospheric NO₂ VCD at NIER/BYI and KMA/AMY, respectively. At urban sites, high NO₂ VCD values were observed under conditions of low wind speed, which were influenced by local urban emissions. Tropospheric NO₂ VCD at HUFS/Yongin increases under conditions of significant transport from urban area of Seoul according to a correlation analysis that considers the transport time lag. Significant diurnal variations were found at urban sites during the MAPS-Seoul campaign, but not at rural sites, indicating that it is associated with diurnal patterns of NO₂ emissions from dense traffic.