Monday, 15 January 2007: 1:30 PM
Dust sandstorm dynamics analysis in Northern China by means of atmospheric, emission, dispersion modeling
212A (Henry B. Gonzalez Convention Center)
The application of Numerical Prediction Models to strong weather phenomena such as dust sandstorm (DSS) is considered of prime importance in the evaluation of control/mitigation measures. In the framework of the WinDust Project, a three-dimensional comprehensive atmospheric, emission, dispersion large-scale model was developed for the northern Asia domain in order to provide a regional characterization of DSS dynamics acting on the area covering Alashan to Beijing. This comprehensive system was based on three different modules: 1) the atmospheric model - Regional Atmospheric Modeling System (RAMS), 2) the dust emission model, called DUSTEM, and 3) the dispersion model - Comprehensive Air quality Model with extensions (CAMx). Using the Reanalysis-2 dataset as atmospheric forcing for RAMS, a three-nested grid approach with different horizontal resolution was adopted. The proposed regional characterization was based on numerical modeling simulations for a relevant DSS events, 20-22 March 2002. These simulations were aimed at inferring large-scale meteorological factors responsible for DSS events affecting the Beijing area and analyzing the DSS dynamics. The performed analyses and modeling activities were carried out to: (i) infer the dust/sand transport dynamics from Alashan to the Beijing target area; (ii) understand the role played respectively by the Alashan area and degraded areas surrounding Beijing in the DSS affecting the capital; (iii) evaluate DSS reduction based on the land cover changes, e.g. implementation of large scale mitigation and control measures. A dynamic downscaling strategy using RAMS model nested into the Reanalysis atmospheric fields (along with a weekly high resolution sea surface temperature datasets) was adopted for all simulations. Specifically, a regional dust coupled model was established through developing dust transport model and embedding it in a non-hydrostatic mesoscale atmospheric model, which simulate and compute the meteorological fields. The dust/sand surface fluxes from remote sources were parameterized based on the friction velocity by developing an emission module that considering the effects of surface cover, moisture and snow. While the dust/sand fluxes from local sources (i.e. abandoned rubble pits in the Beijing area) were estimated based on in situ measurements. By running different emission scenarios, the contribution of the Alashan area to the DSS affecting Beijing was estimated. The effects of mitigations measures in terms of dust/sand emission reduction were evaluated by running future intervention scenarios. Full system implementation and validation, based on both meteorological and dust concentration data, is provided.