First high-resolution tropospheric NO2 observations from the Ultraviolet Visible Hyperspectral Imaging Spectrometer (UVHIS)
Abstract. We present a novel airborne imaging differential optical absorption
spectroscopy (DOAS) instrument: the Ultraviolet Visible Hyperspectral Imaging
Spectrometer (UVHIS), which is developed for trace gas monitoring and
pollution mapping. Within a broad spectral range of 200 to 500  nm and
operating in three channels, the spectral resolution of UVHIS is better than
0.5  nm . The optical design of each channel comprises a fore-optics
with a field of view (FOV) of 40 ∘ , an Offner imaging spectrometer and
a charge-coupled device (CCD) array detector of 1032×1072 pixels. A
first demonstration flight using UVHIS was conducted on 23 June 2018, above an
area of approximately 600  km2 in Feicheng, China, with a spatial
resolution of about 25 m×22 m . Measurements of nadir
backscattered solar radiation of channel 3 are used to retrieve tropospheric
vertical column densities (VCDs) of NO2 with a mean total error of
 3.0×1015 molec cm−2 . The UVHIS instrument clearly
detected several emission plumes transporting from south to north, with a peak
value of 3×1016 molec cm−2 in the dominant one. The
UVHIS NO2 vertical columns are consistent with the ground-based
mobile DOAS observations, with a correlation coefficient of 0.65 for all
co-located measurements, a correlation coefficient of 0.86 for the co-located
measurements that only circled the steel factory and a slight underestimation
for the polluted observations. This study demonstrates the capability of UVHIS
for NO2 local emission and transmission monitoring.