Causmaecker, K. de

Delcloo, A.

Joge Ngale, G.

Laffineur, Q.

Mangold, Alexander

Mattielli, N.

English

KITopen

Koninklijk Meteorologisch InstituutInstitut Royal MétéorologiqueKönigliches Meteorologisches InstitutRoyal Meteorological InstituteEquivalent BC properties during the COVID-19 spring 2020 lockdown period in Brussels, Belgium,compared to non-lockdown periodsA. Mangold, K. De Causmaecker, Q. Laffineur, G. Joge Ngale, N. Mattielli  and A. DelclooUltrafine Particles Air Quality & Climate  5 July 2022AuthorFunctionInstituteOutline ultra-fine particles in urban atmosphere important for air quality relevant part of UFP are light-absorbing particles important sources in cities and residential areas are traffic emissions, domestic heating relative contributions need to be known in order to be able to apply effective reduction measures Covid-19 lockdown / imposed experiment / effect on air quality important to know meteorology important factorAuthorFunctionInstituteInstruments / Location 3 aerosol light absorption coefficient mass concentration oflight-absorbing aerosol 7 wavelengths UV-A to near–IRAethalometerMagee Sci AE31wavelength dependency information on aerosol typeadditional instrumentation (i.a.): nephelometer TSI 3563 ceilometer Vaisala CL 51 meteorological data  Irceline air quality stationsituated in Uccle, a sub-urban, residential area in the South of Brusselsaethalometer data since 2014AuthorFunctionInstitutestudies on Lockdown impact / examples4Vlaamse Milieumaatschappij June 2020Random Forest Modelling / Irceline July 2020Chemical Transport Modellingtraffic in Flanders spring 2020------ freight------ normal carsVRT May 2020, verkeerscentrumlockdown period Belgium18 March – 04 MayAuthorFunctionInstitutemass concentration eq-BC / monthly values 2014 – 20215eq-BC @ 660 nm / ngm-3mean ± stand-dev median / 10- , 90- percentile AuthorFunctionInstituteAbsorption Angstrom Exponent / monthly values 2014 – 20216Absorption Angstrom Exponent calculated between wavelengths 370 and 660 nmAAE = exponential behaviour of absorption between two wavelengthsAAE near  1  marks  fresh combustion (traffic) soothigher AAE  other sources like biomass burning, domestic heating more importantAuthorFunctionInstituteeq-BC and AAE for different time periods7s1 – winters2 – springs3 – summers4 – autumn AuthorFunctionInstituteabsorption coefficient / average day / lockdown period8average values absorption coefficient (Mm-1) lockdown periodfor 2019 for 20202-week periods 2020AuthorFunctionInstituteabsorption coefficient / average day / lockdown period9Interpretation• all four periods show distinctly lower values than 2019 and 2014-18 period• 2nd half of March 2020  highest values – relatively cold,  stable conditions during night and morning• morning ‘rush-hour’ peak visible in three of the four periods (stable conditions during morning; still traffic, in particular freight)• lowest values in 1st half of April (incl Easter) and 1st half of May (incl long weekend over 1 May) clearly lower absorption coefficient during Covid-lockdown compared to former yearsAuthorFunctionInstitutesource regions and meteorology 10Dispersion model:Lagrangian particle transport model FLEXPART 9.02 in backward mode period: 01-Dec-2013  to  30-Nov-2021;  3-hourlyMeteo data input:3-hourly data with 0.5° grid resolution from ECMWF  ERA-5output:potential source regions or ‘residence time’;  relates to the chance that air arrived at sample site at a given day passed over that regiongrouped according to year / season / vertical level / lockdown period / ‘local radius’ around sample site (50 km)vertical levels ( m agl ):l1 = 0 – 100   /  l2 = 100 – 200   /  l3 = 200 – 500   /  l4 = 500 – 1000  /  l5 = 1000 – 2000 l6 = 2000 – 5000 AuthorFunctionInstitutesource regions lockdown period112019vertical level0-100 m agl2020vertical level0-100 m aglwindroses 10 mAuthorFunctionInstitutelockdown period and ‘local’ source region12deviation fromthe averagelockdown periodper layer !AuthorFunctionInstitutelockdown period and height level contribution13deviation fromthe averagelockdown periodAuthorFunctionInstitutelockdown period and parameter deviation14deviation fromthe averagelockdown periodfrom RMI-Climato-Dep:less precipitationlonger sunshine duration AuthorFunctionInstituteSUMMARY15Lockdown-period:• absorption coefficient distinctly lower• daily cycle of absorption coefficient distinctly less pronounced • AAE distinctly higher values and daily cycle less pronounced fresh combustion aerosol (~ traffic soot) decreases  absorbing aerosol from other sources (most probably heating) more relative weightbut – 2021 similar values Disentangling lockdown effect – meteorology  • meteorology different during lockdown period 2020• wind speed lower  /   less precipitation  /  higher sunshine duration• within lower vertical levels (0 – 1000 m) higher share of ‘local’ contribution• but higher vertical levels (1000 – 5000 m) higher share of ‘local’-total contribution more locally and from higher up meteo signal ambiguous – not only pointing to better/worse air quality conditionsIn general, period 2014 – 2021:• eq-BC mass concentration  decreasing trend – yearly, seasonal • Absorption Angstrom Exponent  increasing trend – yearly, seasonal AuthorFunctionInstitute16Thank you very much

Equivalent BC properties during the COVID 19 spring 2020 lockdown period in Brussels, Belgium, compared to non lockdown periods

https://publikationen.bibliothek.kit.edu/1000158355/150666060

Equivalent BC properties during the COVID 19 spring 2020 lockdown period in Brussels, Belgium, compared to non lockdown periods

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