[1] During the last decade, several numerical schemes have been deployed for the simulation of mineral dust processes in the atmosphere. The developed models have various deficiencies in the representation of dust particle physical properties and effects on climate. On the basis of the present status of the dust modeling tools, a combined effort was devoted to upgrading the SKIRON/Dust forecasting system by incorporating new features for the description of the lower boundary characteristics of the atmospheric model and the dust aerosol properties. In this paper, the updated model version is presented along with sensitivity simulations and evaluation of the model results with available observational data. The analysis is separated into two main parts, namely, the improvements that correspond to the atmospheric modeling system SKIRON and the upgrading of the physical mechanisms incorporated in the dust transport submodel. The analysis showed that the incorporation of the new model correction schemes led to a better and more accurate representation of the processes concerning meteorology and dust properties. The new soil characterization schemes significantly improve the energy-partitioning predictions at the surface and therefore the boundary layer processes that play a substantial role in the determination of the dust production mechanisms. Significant differences were detected in the radiation balance between atmosphere and ground surface by incorporating statistical corrections for the description of terrain slopes and azimuths, mainly in areas with highly rough terrain. Finally, the more accurate description of the transported dust aerosol distribution (eight size bins) and the new dust production and deposition schemes led to more efficient determination of the dust particle optical properties (aerosol optical depths).Citation: Spyrou, C., C. Mitsakou, G. Kallos, P. Louka, and G. Vlastou (2010), An improved limited area model for describing the dust cycle in the atmosphere,

Here we describe the development of the London Hybrid Exposure Model (LHEM), which calculates exposure of the Greater London population to outdoor air pollution sources, in-buildings, in-vehicles, and outdoors, using survey data of when and where people spend their time. For comparison and to estimate exposure misclassification we compared Londoners LHEM exposure with exposure at the residential address, a commonly used exposure metric in epidemiological research. In 2011, the mean annual LHEM exposure to outdoor sources was estimated to be 37% lower for PM and 63% lower for NO than at the residential address. These decreased estimates reflect the effects of reduced exposure indoors, the amount of time spent indoors (∼95%), and the mode and duration of travel in London. We find that an individual's exposure to PM and NO outside their residential address is highly correlated (Pearson's R of 0.9). In contrast, LHEM exposure estimates for PM and NO suggest that the degree of correlation is influenced by their exposure in different transport modes. Further development of the LHEM has the potential to increase the understanding of exposure error and bias in time-series and cohort studies and thus better distinguish the independent effects of NO and PM.

Abstract. The desert of Sahara is one of the major sources of mineral dust on Earth, producing around 2×108 tons/yr. Under certain weather conditions, dust particles from Saharan desert get transported over the Mediterranean Sea and most of Europe. The limiting values set by the directive EC/30/1999 of European Union can easily be exceeded by the transport of desert dust particles in the south European Region and especially in urban areas, where there is also significant contribution from anthropogenic sources. In this study, the effects of dust transport on air quality in several Greek urban areas are quantified. PM10 concentration values from stationary monitoring stations are compared to dust concentrations for the 4-year period 2003–2006. The dust concentration values in the Greek areas were estimated by the SKIRON modelling system coupled with embedded algorithms describing the dust cycle. The mean annual dust contribution to daily-averaged PM10 concentration values was found to be around or even greater than 10% in the urban areas throughout the years examined. Natural dust transport may contribute by more than 20% to the annual number of exceedances – PM10 values greater than EU limits – depending on the specific monitoring location. In a second stage of the study, the inhaled lung dose received by the residents in various Greek locations is calculated. The particle deposition efficiency of mineral dust at the different parts of the human respiratory tract is determined by applying a lung dosimetry numerical model, which incorporates inhalation dynamics and aerosol physical processes. The inhalation dose from mineral dust particles was greater in the upper respiratory system (extrathoracic region) and less significant in the lungs, especially in the sensitive alveolar region. However, in cases of dust episodes, the amounts of mineral dust deposited along the human lung are comparable to those received during exposure in heavily polluted urban or smoking areas.

Mineral dust aerosols exert a significant effect on both solar and terrestrial radiation. By absorbing and scattering, the solar radiation aerosols reduce the amount of energy reaching the surface. In addition, aerosols enhance the greenhouse effect by absorbing and emitting outgoing longwave radiation. Desert dust forcing exhibits large regional and temporal variability due to its short lifetime and diverse optical properties, further complicating the quantification of the direct radiative effect (DRE). The complexity of the links and feedbacks of dust on radiative transfer indicate the need for an integrated approach in order to examine these impacts.

In order to examine these feedbacks, the SKIRON limited area model has been upgraded to include the RRTMG (Rapid Radiative Transfer Model – GCM) radiative transfer model that takes into consideration the aerosol radiative effects. It was run for a 6 year period. Two sets of simulations were performed, one without the effects of dust and the other including the radiative feedback. The results were first evaluated using aerosol optical depth data to examine the capabilities of the system in describing the desert dust cycle. Then the aerosol feedback on radiative transfer was quantified and the links between dust and radiation were studied. The study has revealed a strong interaction between dust particles and solar and terrestrial radiation, with several implications on the energy budget of the atmosphere. A profound effect is the increased absorption (in the shortwave and longwave) in the lower troposphere and the induced modification of the atmospheric temperature profile. These feedbacks depend strongly on the spatial distribution of dust and have more profound effects where the number of particles is greater, such as near their source