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Long-term observations of NO2, SO2, HCHO, and CHOCHO over the Himalayan foothills: Insights from MAX-DOAS, TROPOMI, and GOME-2

dc.contributor.authorRawat, P.
dc.contributor.authorNaja, M.,
dc.contributor.authorRajwar, M.C.
dc.contributor.authorIrie, H.
dc.contributor.authorLerot, C.
dc.contributor.authorKumar, M.
dc.contributor.authorLal, S.
dc.date2024
dc.date.accessioned2024-08-21T06:13:04Z
dc.date.available2024-08-21T06:13:04Z
dc.identifier.urihttps://orfeo.belnet.be/handle/internal/13414
dc.descriptionRegional air pollution has become one of the utmost environmental concerns in India, especially over economically vibrant and densely populated regions, such as Northern India, including the Indo-Gangetic Plain (IGP). Additionally, the Himalayas adjacent to IGP provide conducive conditions to confine pollutants and transport them to greater horizontal and vertical extents. However, in-situ observations are sparse and limited over the Himalayas, where data retrievals from space-based sensors are fraught with difficulties. In light of this, observations of NO2, SO2, HCHO, and CHOCHO are made from a Himalayan foothills site (Pantnagar, 29.03o N, 79.47o E and 237 AMSL) utilizing remote sensing observation of Multi-AXis-Differential Optical Absorption Spectroscopy (MAX-DOAS). Data from TROPOspheric Monitoring Instrument (TROPOMI), and Global Ozone Monitoring Experiment-2 (GOME-2) satellite instruments are also presented. We investigate the temporal variations in near-surface mixing ratios, vertical profiles, and tropospheric columns of these trace gases from January 2017 to December 2020. The diurnal variation of NO2 and HCHO at different altitude regions (surface to 3 km) were typically urban-type with morning and evening peaks. At the same time, the CHOCHO diurnal variation peaks in the noon hours. We observed annual mean tropospheric NO2 vertical column densities (VCDs) of 3.2 × 1015 (unit: molecules/cm2), tropospheric SO2 VCDs of 1.2 × 1016, tropospheric HCHO VCDs of 1.6 × 1016, and tropospheric CHOCHO VCDs of 0.6 × 1015 from MAX-DOAS observations. MAX-DOAS comparison with the TROPOMI and GOME-2 VCDs shows an underestimation of up to 48% for satellite NO2 VCDs, while SO2 and HCHO VCDs show nominal biases in the range of 20–30%. The Rgf sensitivity calculation shows prominent biogenic sources of VOCs during noon hours, while Rfn calculation mostly shows a NOx-limited ozone production regime over the Himalayan foothill site. The Rfn monthly variations match reasonably well between the MAX-DOAS and TROPOMI, while Rgf values were higher from satellite observations. This study highlights the factors governing the diurnal and monthly variation of different pollutants over the Himalayan foothill region and asses the space-borne observations for better utilization.
dc.languageeng
dc.titleLong-term observations of NO2, SO2, HCHO, and CHOCHO over the Himalayan foothills: Insights from MAX-DOAS, TROPOMI, and GOME-2
dc.typeArticle
dc.subject.frascatiEarth and related Environmental sciences
dc.audienceScientific
dc.subject.freeAir pollution
dc.subject.freeMAX-DOAS
dc.subject.freeIndo-gangetic plain
dc.subject.freeNO
dc.subject.freeSO
dc.subject.freeVOCs
dc.subject.freeHimalayan foothills
dc.source.titleAtmospheric Environment
dc.source.volume336
dc.source.pageA120746
Orfeo.peerreviewedYes
dc.identifier.doi10.1016/j.atmosenv.2024.120746
dc.identifier.url


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