English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

. Nitrogen dioxide ( NO2 ), produced as a result of fossil fuelcombustion, biomass burning, lightning, and soil emissions, is a key urbanand rural tropospheric pollutant. In this case study, ground-based remotesensing has been coupled with the in situ network in Vienna, Austria, toinvestigate NO2 distributions in the planetary boundary layer.Near-surface and path-averaged NO2 mixing ratios within themetropolitan area of Vienna are estimated from car DOAS (differential opticalabsorption spectroscopy) zenith-sky and tower DOAS horizon observations. Thelatter configuration is innovative in the sense that it obtains horizontalmeasurements at more than a hundred different azimuthal angles – within a360 ∘ rotation taking less than half an hour. Spectral measurementswere made with a DOAS instrument on nine days in April, September, October,and November 2015 in the zenith-sky mode and on five days in April andMay 2016 in the off-axis mode. The analysis of tropospheric NO2 columns from the car measurements and O4 normalized NO2 path averages from the tower observations provide interesting insights intothe spatial and temporal NO2 distribution over Vienna. Integratedcolumn amounts of NO2 from both DOAS-type measurements areconverted into mixing ratios by different methods. The estimation ofnear-surface NO2 mixing ratios from car DOAS tropospheric NO2 vertical columns is based on a linear regression analysisincluding mixing height and other meteorological parameters that affect thedilution and reactivity in the planetary boundary layer – a new approach forsuch conversion. Path-averaged NO2 mixing ratios are calculatedfrom tower DOAS NO2 slant column densities by taking into accounttopography and geometry. Overall, lap averages of near-surface NO2 mixing ratios obtained from car DOAS zenith-sky measurements, around acircuit in Vienna, are in the range of 3.8 to 26.1 ppb and in good agreementwith values obtained from in situ NO2 measurements for days withwind from the southeast. Path-averaged NO2 mixing ratios at 160 mabove the ground as derived from the tower DOAS measurements are between 2.5and 9 ppb on two selected days with different wind conditions and pollutionlevels and show similar spatial distribution as seen in the car DOASzenith-sky observations. We conclude that the application of the two methodsto obtain near-surface and path-averaged NO2 mixing ratios ispromising for this case study.

atmospheric chemistry and physics

Near-surface and path-averaged mixing ratios of NO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; derived from car DOAS zenith-sky and tower DOAS off-axis measurements in Vienna: a case study