Retrieval of NO2 Column Amounts from Ground-Based Hyperspectral Imaging Sensor Measurements

Abstract

Total column amounts of NO2 (TCN) were estimated from ground-based hyperspectral imaging sensor (HIS) measurements in a polluted urban area (Seoul, Korea) by applying the radiance ratio fitting method with five wavelength pairs from 400 to 460 nm. We quantified the uncertainty of the retrieved TCN based on several factors. The estimated TCN uncertainty was up to 0.09 Dobson unit (DU), equivalent to 2.687 × 1020 molecules m−2) given a 1° error for the observation geometries, including the solar zenith angle, viewing zenith angle, and relative azimuth angle. About 0.1 DU (6.8%) was estimated for an aerosol optical depth (AOD) uncertainty of 0.01. In addition, the uncertainty due to the NO2 vertical profile was 14% to 22%. Compared with the co-located Pandora spectrophotometer measurements, the HIS captured the temporal variation of the TCN during the intensive observation period. The correlation between the TCN from the HIS and Pandora also showed good agreement, with a slight positive bias (bias: 0.6 DU, root mean square error: 0.7 DU).

Airborne observation with a low-cost hyperspectral instrument: Retrieval of NO2 VCD and the satellite sub-grid variability over industrial point sources

“…On the other hand, the HIS exhibits sufficient sensitivity at the VIS range (350-500 nm), where the spectral absorption characteristics of NO2 are well distinguished, making it suitable for NO2 VCD retrievals. For instance, Park et al (2019) retrieved NO2 VCD from ground-based observations of the diffuse radiances using the identical instrument (i.e., HIS) and presented its compatibility for NO2 VCD retrievals by demonstrating a high correlation (R=0.84) with collocated Pandora observations. However, there are several vulnerabilities on the HIS that hinder its utilization for airborne observations, primarily due to low-quality optical and radiometric characteristics resulting from its compact configuration and lack of regular or meticulous maintenance.…”

Changes of NOx in urban air detected with monitoring VIS-NIR field spectrometer during the coronavirus pandemic: A case study in Germany

“…However, previous studies indicate typical absorption cross-sections for opto-electronic detection of the urban air pollutant also in the VIS-NIR range ( Zheng et al, 2018 ). Furthermore, high-grade imaging UV-VIS sensors and UV-VIS point-spectrometers have measured columnar amounts of NO2 in the atmosphere ( Park et al, 2019 ). Thus, it may be possible to consider also inexpensive VIS-NIR spectrometer systems as suitable devices for detecting NO2 pollution in urban air through the continuous monitoring of downwelling light passing through the earth's atmosphere.…”

Spectrum-free integrated photonic remote molecular identification and sensing

“…Absorption spectroscopy is an important tool for the determination of molecular composition where direct interaction with a target is not practical or feasible. Typical applications range from the measurement of trace gases in the atmosphere 1,2 , gas emissions 3 , hyperspectral ground 4 and satellite-based 5 remote sensing platforms, to deep-sky and solar system astronomical spectroscopy 6, 7 . Many other high sensitivity molecular spectroscopy techniques have been pursued using active techniques such as dual comb spectroscopy 8-11 but these require laser sources, complex electronics and optics, and cannot probe distant targets.…”