https://repository.cyi.ac.cy/handle/123456789/849 2026-05-01T03:31:22Z https://repository.cyi.ac.cy/handle/CyI/2632 Title: Physical and Chemical characteristics of atmospheric new particle formation (NPF) in Cyprus Authors: Deot, Neha Abstract: Aerosols are small solid or liquid particles suspended in the atmosphere. They have two origins; the particles can be either primarily emitted or formed secondary. The precursor to secondary aerosol formation is new particle formation (NPF). Atmospheric NPF is a process by which new particles are formed via gas-to-particle phase conversion in the presence of precursor gases, usually low in volatility. This study aims to better understand the formation and growth mechanisms behind atmospheric NPF. NPF is a major source of aerosols (up to 80% of aerosol number concentration globally) and cloud condensation nuclei (CCN). Depending on their size, they can have significant direct or indirect effects on climate and human health. According to our current knowledge and observations, sulphuric acid (H2SO4), iodic acid (IO3), ammonia (NH3), and dimethylamine (DMA - (CH3)2NH) are present to form the initial molecular clusters during the formation of new particles. Later, these molecular clusters grow into larger aerosol particles by condensation of atmospheric vapors such as methanesulfonic acid (MSA), and highly oxygenated organic compounds (HOMs). Many studies have been carried out to understand the role of all these acids and organic compounds in forming aerosol particles. However, there is still much to be understood, such as the detailed formation and growth mechanisms of these aerosol particles that are not adequately represented by current modeling frameworks. The main objective of this PhD study is to better understand the formation and growth of nanometre-sized aerosol particles and aerosol precursor molecules in the Eastern Mediterranean and Middle East (EMME) region. These areas are the hotspots of climate change with strong heat waves and dust pollution and are surrounded by three continents (Europe, Africa, and Asia) and lack observations of aerosol precursors. The aim is to link relevant aerosol precursor molecule observations using the latest mass spectrometric methods to NPF events. For this, I have an aim to do field measurements using the network of Cyprus Atmospheric Observatory (CAO) in order to study aerosol number concentrations and the composition of air ions at the sites. 2024-11-01T00:00:00Z https://repository.cyi.ac.cy/handle/CyI/2626 Title: ANTHROPOGENIC NH3 IN THE UPPER TROPOSPHERE: IMPACTS ON GLOBAL PARTICLE FORMATION AND THE ASIAN TROPOPAUSE AEROSOL LAYER Authors: Xenofontos, Christos Abstract: Anthropogenic ammonia (NH3) emissions have risen substantially in recent decades, primarily due to agricultural intensification, altering atmospheric composition and influencing aerosol– cloud–climate interactions. While the effects of NH3 on surface air quality are well recognized, its role in aerosol formation in the upper troposphere–lower stratosphere (UTLS) remains poorly quantified. We use the EMAC Earth system model, incorporating new particle formation (NPF) parameterizations from the CERN CLOUD experiment, to assess the global and regional effects of anthropogenic NH3 on UTLS aerosol processes. Global simulations reveal that convective transport of boundary-layer NH3 substantially enhances NPF in the UTLS, increasing formation rates by one to three orders of magnitude compared to a scenario without anthropogenic NH3. This enhancement doubles aerosol number concentrations and leads to a 2.5-fold increase in cloud condensation nuclei (CCN) abundance. Anthropogenic NH3 emissions further modify aerosol composition, enhancing the contribution of water-soluble inorganic ions to the UTLS aerosol optical depth (AOD) by 20% and increasing total column AOD by up to 80%. A focused regional analysis over South Asia shows that during the summer monsoon, deep convection transports large quantities of NH3 into the UTLS, promoting NH3-driven particle formation and contributing to the development of the Asian Tropopause Aerosol Layer (ATAL). Diurnal cycle analysis indicates that NPF is strongest during daytime, with a tenfold enhancement in formation rate and up to an 80% increase in CCN at cloud-forming altitudes. NH3 also drives pronounced changes in aerosol composition, with an order-of-magnitude increase in nitrate content and a regional AOD enhancement of up to 70%. Together, these findings demonstrate that anthropogenic NH3 emissions exert a profound and previously underexplored influence on upper tropospheric particle formation, cloud-relevant aerosol populations, and radiative properties—from regional monsoon systems to the global climate. 2026-02-09T00:00:00Z https://repository.cyi.ac.cy/handle/CyI/2170 Title: Air Quality Modelling over Cyprus Authors: Georgiou, Georgios Abstract: The WRF-Chem model is employed to study air pollution, the intense photochemical activity, and their impact on air quality over the eastern Mediterranean, focusing on Cyprus. The CBMZ-MOSAIC, MOZART-MOSAIC, and RADM2-MADE/SORGAM gas-phase chemistry and aerosol mechanisms are intercompared during summertime, using measurements from a dense network of 14 ground stations in Cyprus. Tropospheric ozone concentrations were overestimated by all three mechanisms (9% ≤ NMB ≤ 23%) with the smaller mean bias (4.25 ppbV) obtained by RADM2-MADE/SORGAM. Differences in ozone concentrations can be attributed to the VOC treatment by the three mechanisms. For fine particulate matter (PM2.5 ), the lowest mean bias (9 µgm−3 ) was obtained by RADM2-MADE/SORGAM, with overestimates in sulphate and ammonium aerosols. The MOSAIC aerosol mechanism was found to overestimate PM2.5 concentrations by up to 22 µgm−3 due to a more pronounced dust component, mostly influenced by dust inflow from the model boundaries. The model output using i) the EDGAR emission inventory, ii) a new, up-to-date and high spatiotemporal resolution anthropogenic emission inventory for Cyprus, and iii) zero anthropogenic emissions was compared with measurements from background and urban ground stations in Cyprus. After incorporating high spatiotemporal resolution emissions, the normalized mean bias between the modelled and observed NOx mixing ratios at urban sites was reduced from -67% to -29% and from -51% to -10% for the winter and summer respectively. In line with this, the overestimation in O3 mixing ratios was reduced from 45% to 28% during the winter and from 25% to 19% during summer. Taking into account the diurnal variability in the emission inventory was demonstrated to be crucial for the accurate simulation of the daily profiles of NOx and O3 at urban sites. 2020-01-01T00:00:00Z https://repository.cyi.ac.cy/handle/CyI/2169 Title: Improving hydrological-process representation in a distributed hydrological model towards fully coupled atmospheric-hydrological simulations Authors: Sofokleous, Ioannis Abstract: The distributed hydrological model WRF-Hydro and the state-of-the-art atmospheric model WRF are used in this thesis to study the potential of improving the simulation of hydrometeorological variables in Mediterranean areas through coupled atmospheric – hydrological simulations. The specific objectives are: (i) to identify the most skillful WRF parameterizations for precipitation simulations at 1-km resolution, (ii) to improve equations of WRF-Hydro parameterizations and to apply a grid-based calibration approach, and (iii) to evaluate the performance of the fully coupled WRF-Hydro model. The study area is the Mediterranean island of Cyprus and 31 watersheds in the Troodos mountains. Simulated precipitation and streamflow are assessed on a daily and annual basis for seven hydrologic years from 2011 to 2018. A comprehensive evaluation approach and a new metric for extreme events were proposed for the selection of a skillful subset of five out of 18 combinations of WRF parameterizations (members) for precipitation simulations. The WRF-Hydro groundwater bucket model was modified to include losses, which reduced the streamflow overestimation by 30%. The modification of the Jarvis stomatal conductance equation to include nocturnal transpiration reduced the underestimation and reproduced the observed annual evapotranspiration (85% of precipitation). The grid-based calibration efficiently calibrated the hydrological model parameters for different elevation, land use and geological classes. WRF-Hydro, forced by the five WRF members, captured the streamflow of 31 watersheds, with a Nash-Sutcliffe efficiency for daily streamflow ranging up to 0.8. The fully coupled WRF-Hydro was found to yield increased precipitation (3%) and evapotranspiration (33%), relative to the standalone WRF model. This thesis showed that WRF-Hydro with the above modifications can reproduce the water balance components in a semi-arid environment. These findings are indicative of the applicability of WRF-Hydro in a coupled mode with WRF for water balance investigations under current conditions and for future climate and land use changes.   2023-10-12T00:00:00Z