AS3.2

Major efforts are currently put to reduce drastically PM emissions at the exhaust of the most recent vehicles, however, little is done to mitigate non-tail-pipe emissions and resuspended road dust, in particular. Such traffic-related resuspension of dust may become a major source of PM10 at a time our cars are becoming cleaner. This may be particularly true in (semi-)arid urban environments which are characterized by high deposition rates of desert dust and low rain wash-out rates of roads.

Near-real-time (10-min time resolution) on-line measurement of selected cations (Na⁺, Mg²⁺, Ca²⁺) in PM10 were performed using a Particle-into-liquid-sampler (PILS) coupled with an Ion Chromatograph (IC). Such high temporal resolution of these species has been rarely reported in literature and to the best of our knowledge, it is the first time that such dense observations are reported in PM10 for urban environment. These measurements were performed during a 3-month transition period between (from wet winter to dry summer) at an urban background site of Nicosia (Cyprus) a central location of the Eastern Mediterranean Middle East (EMME) region.

The consistency of these measurements was successfully assessed against 24-h integrated filter-based measurements while hypotheses related to the use of Calcium as a tracer of dust particles further verified against trace metal analysis. A comprehensive suite of co-located ancillary data (Aethalometer, Lidar, ACSM, SMPS, OPC) were used to further support the daily/weekly/monthly variability of Calcium concentration in PM10.

Diurnal variability of dust concentration in PM10 at our background urban site displayed a strong and intense traffic-related source at rush hours together with a maximum observed in the afternoon in phase with the development of the Planetary Boundary Layer and intrusion of desert dust from aloft. Interestingly, this pattern is amplified when moving from wet to dry months and encompassing the Spring dust season.

The contribution of the two dust sources in PM10 (traffic-related dust resuspension and intrusion of long-range transported desert dust) is provided here for different temporal scales (day, week, month). Estimate of traffic-related (non-)tail-pipe emissions (ie. combustion carbonaceous vs resuspended dust) is also provided here highlighting the dominant role of dust in PM10 emissions from road transport sector.

How to cite: Sciare, J., Sarda-Estève, R., Oikonomou, K., Bimenyimana, E., Pikridas, M., Unga, F., and Christodoulou, A.: Real-time source apportionment of local vs regional dust in a semi-arid urban environment of the Eastern Mediterranean Middle East (EMME) region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14115, https://doi.org/10.5194/egusphere-egu21-14115, 2021.

Windblown dust, emitted from the surface of the earth to the atmosphere as a result of the disintegration of material due to wind drag, can have a significant impact on the atmospheric concentration of PM, especially over (semi-)arid areas. They however may be important occasionally also over non-arid regions with considerable precipitation (e.g. over midlatitudes). Therefore their contribution to the total PM pollution cannot be neglected, especially considering the increasing potential of droughts in a changing climate, when long dry periods occur between precipitation events.

Here, we investigate the regional impact of PM emissions from wind erosion on urban PM levels for a central European domain using a well-established windblown dust module (called ‘‘WBDUST’’) for the 2018-2019 period. As driving meteorological data, we used WRF simulations. Before applying WBDUST, we made some modifications which ensured that the surface heterogeneity for vegetation cover is taken into account. This is important as for grid cells, where the average leaf-area-index (LAI) is higher than a certain threshold, zero emissions would be produced. However, if we take into account the fractional character of LAI, emissions will be more realistic. The obtained emission fluxes were comparable to anthropogenic ones indicating the great importance of windblown dust even over such non-arid areas. WBDUST emissions were implemented into the CAMx chemistry transport model and we performed simulations with and without these emissions. Our results showed that urban PM levels are significantly higher if wind-blown dust is considered and match better with observations.

How to cite: Liaskoni, M., Bartik, L., and Huszar, P.: Modeling the regional dust emissions in central Europe and their contribution to urban PM levels, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3863, https://doi.org/10.5194/egusphere-egu21-3863, 2021.

We studied sulfate aerosols over the Southern Ocean using the atmosphere-only climate model HadGEM3-GA7.1. The model contains biases in the aerosol seasonal variability over the Southern Ocean (40°S to 60°S), which cascade to uncertainties in aerosol-cloud interactions. Aerosols over the Southern Ocean are primarily natural in origin, such as sea spray aerosol and sulfate aerosol formed by phytoplankton-produced dimethyl sulfide (DMS).

The current sulfate chemistry scheme implemented in the model simplifies the oxidation pathways for DMS, which has been identified as a major source of the seasonal bias present. The simulations performed here incorporate a comprehensive sulfate scheme in both the gas and aqueous-phase. An intermediate complexity biogeochemical dynamic model, MEDUSA, simulated a global climatology of seawater DMS, which is compared with a seawater DMS observational dataset from 2011. We compared the seasonality of sulfate aerosols over the Southern Ocean, and the global distribution using the two seawater DMS climatologies. Simulated aerosols over the Southern Ocean were evaluated against satellite and in-situ observations. The results show the impact of seawater DMS on sulfate aerosols and their influence on cloud formation.

How to cite: Bhatti, Y., Revell, L., McDonald, A., and Willaims, J.: Global Climate Model Simulations of Natural Aerosols over the Southern Ocean, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-195, https://doi.org/10.5194/egusphere-egu21-195, 2021.

We present the results of the AEROMARINE field campaign which took place in the boreal spring 2019 off the coast of Reunion island in the South West Indian Ocean basin. The southern Indian Ocean is of major interest for the study of marine aerosols, their distribution and variability [1]. Nine instrumented light plane flights and a ground-based microwave radiometer were used during the AEROMARINE field campaign. These measurements were compared with the long-term measurements of the AERONET sun-photometer (based in Saint Denis, Reunion Island) and various instruments of the high altitude Maido Observatory (2200m above sea level, Reunion island). These results were analyzed using different model outputs: (i) the AROME mesoscale weather forecast model to work on the thermodynamics of the boundary layer, (ii) the FLEXPART-AROME Lagrangian particle dispersion model to assess the geographical and vertical origin of air masses, and (iii) the chemical transport model CAMS (Copernicus Atmosphere Monitoring Service) to work on the aerosol chemical composition of air masses. These measurements allowed us to determine the background concentration of natural marine aerosols and to highlight that (1) the atmospheric layers above 1500m are in the free troposphere and are mainly composed of aerosols from the regional background and (2) that the local environment (ocean or island) has little impact on the measured concentrations. Marine aerosols emitted locally are mostly measured in the lower atmospheric layers (below 500m). The daytime marine aerosol distributions in the free troposphere measured by the aircraft were compared to the aerosol distribution measured at the high altitude Maido observatory at night when the observatory is located in the free troposphere.  We also found that the CAMS reanalyses overestimated the aerosol optical depth in this region. Finally, our study confirms, with no ambiguity, that the AERONET station in Saint Denis (Reunion island) can be considered as a representative marine station in the tropics [2]. 

References
[1]  I.  Koren,  G.  Dagan,  and  O.  Altaratz.   From  aerosol-limited  to  invigoration  of  warm  convective clouds. Science, 344 (6188) : 1143–1146, 2014.
[2]  P. Hamill, M. Giordano, C. Ward, D. Giles, and B. Holben.  An aeronet-based aerosol classification using the mahalanobis distance. Atmospheric Environment, 140 : 213–233,2016.

How to cite: Mascaut, F., Pujol, O., Brioude, J., Verreyken, B., Peroni, R., Blarel, L., Podvin, T., metzger, J.-M., Sellegri, K., and Goloub, P.: Aerosol characterization in an oceanic context around Reunion island (AEROMARINE field campaign), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2729, https://doi.org/10.5194/egusphere-egu21-2729, 2021.