No abstract

The aim of this research is to provide a detailed characterization of spatial patterns and temporal trends in the regional and local dust source areas within the desert of the Alashan Prefecture (Inner Mongolia, China). This problem was approached through multi‐scale remote sensing analysis of vegetation changes. The primary requirements for this regional analysis are high spatial and spectral resolution data, accurate spectral calibration and good temporal resolution with a suitable temporal baseline. Landsat analysis and field validation along with the low spatial resolution classifications from MODIS and AVHRR are combined to provide a reliable characterization of the different potential dust‐producing sources. The representation of intra‐annual and inter‐annual Normalized Difference Vegetation Index (NDVI) trend to assess land cover discrimination for mapping potential dust source using MODIS and AVHRR at larger scale is enhanced by Landsat Spectral Mixing Analysis (SMA). The combined methodology is to determine the extent to which Landsat can distinguish important soils types in order to better understand how soil reflectance behaves at seasonal and inter‐annual timescales. As a final result mapping soil surface properties using SMA is representative of responses of different land and soil cover previously identified by NDVI trend. The results could be used in dust emission models even if they are not reflecting aggregate formation, soil stability or particle coatings showing to be critical for accurately represent dust source over different regional and local emitting areas. Copyright © 2012 John Wiley & Sons, Ltd.

Dust intrusions from African desert regions have an impact on the Mediterranean Basin (MB), as they cause an anomalous increase of aerosol concentrations in the tropospheric column and often an increase of particulate matter at the ground level. To estimate the Saharan dust contribution to PM 10 , a significant dust intrusion event that occurred in June 2006 is investigated, joining numerical simulations and specific measurements. As a first step, a synoptic analysis of this episode is performed. Such analysis, based only on meteorological and aerosol optical thickness observations, does not allow the assessment of exhaustive informations. In fact, it is not possible to distinguish dust outbreaks transported above the boundary layer without any impact at the ground level from those causing deposition. The approach proposed in this work applies an ad hoc model chain to describe emission, transport and deposition dynamics. Furthermore, physical and chemical analyses (PIXE analysis and ion chromatography) were used to measure the concentration of all soil-related elements to quantify the contribution of dust particles to PM 10 . The comparison between simulation results and in-situ measurements show a satisfying agreement, and supports the effectiveness of the model chain to estimate the Saharan dust contribution at ground level.

Comprehensive modelling of dust events requires a full physical representation of small‐scale emission mechanisms and description of long‐range transport dynamic. In this paper we propose a simulation system that integrates three different models in order to represent the whole dust cycle. The RAMS atmospheric model configuration has two nested grids, at 50 km and 10 km horizontal resolution, and is used to force both the dust emission model DUSTEM, and the transport model CAMx. The performance of the three‐model simulation system was evaluated using a major dust storm that occurred in March 2002 in the desert of the Alashan Prefecture (Inner Mongolia, China) and which had a significant impact over a large area in northern China. In order to identify potential active dust sources, a specific remote sensed analysis, calibrated through a field campaign in the Alashan Prefecture region, has been assimilated in the modelling system. Simulated dust storm features, from the higher resolution grid, are in good agreement with observed data: surface wind values discrepancies are less than 2 m/s in the Alashan area and less than 5 m/s along the dust storm track. In comparison to ground observations, the modelled dust surface concentration peaks in Beijing differ by only 2 mg/m3 although the timing of dust peaks is delayed in the model. As a consequence this integrated numerical model, along with the remote sensed land surface characterization, is suggested to be a practical and flexible tool for simulating and analysing the whole dust storm dynamics. Copyright © 2013 John Wiley & Sons, Ltd.