ALBERT

Description: A method for direct normal irradiance (DNI) forecasting for specific sites is proposed. It is based on the combination of a numerical weather prediction (NWP) model, which provides cloud information, with radiative transfer simulations fed with external aerosol forecasts. The NWP model used is the ECMWF Integrated Forecast System, and the radiative transfer information has been obtained from the Library of Radiative Transfer (libRadtran). Two types of aerosol forecasts have been tested: the global Monitoring Atmospheric Composition and Climate (MACC) model, which predicts five major components of aerosols, and the Dust Regional Atmospheric Model (BSC-DREAM8b) added to a fixed background calculated as the 20th percentile of the monthly mean of AERONET 2.0 observations from a different year. The methodology employed is valid for all meteorological situations, providing a stable and continuous DNI curve. The performance of the combined method has been evaluated against DNI observations and compared with the pure ECMWF forecasts at eight locations in the southern half of mainland Spain and the Canary Islands, which received high loadings of African dust for 2013 and 2014. Results for 1-day forecasts are presented. Although clouds play a major role, aerosols have a significant effect, but at shorter time scales. The combination of ECMWF and MACC forecasts gives the best global results, improving the DNI forecasts in events with high aerosol content. The regional BSC-DREAM8b yields good results for some extremely high dust conditions, although more reliable predictions, valid for any aerosol conditions, are provided by the MACC model.

Description: From end of February until March 2009 and July 2009 the experimental campaign named DAURE took place in northeastern Spain in both an urban and rural sites (Barcelona city and Montseny Natural Park) with the main objective of studying the formation and transport processes of particulate matter in the region. Several groups collaborated in an extensive measurement campaign with aerosol monitoring, meteorological measurements, atmospheric vertical structure retrievals from LIDAR and supported by numerical simulations of the meteorological and air quality conditions over the region. In this article, we present a description of the main meteorological conditions that affected the Barcelona geographical area during the campaign. The main synoptic conditions are identified and discussed by means of meteorological observations and numerical weather prediction models. Furthermore, a detailed analysis of the local meteorological conditions during the campaign is also presented. The characteristic surface wind field and the vertical structure of the main flows affecting Barcelona and the Montseny rural site are discussed using high-resolution mesoscale meteorological simulations, vertical profiles of LIDAR measurements, radiosoundings, and analysis of backward dispersion simulations with a Lagrangian model. The analysis permits the identification of three main meteorological regimes for the winter campaign (February and March 2009): a first regime dominated by high-pressure conditions over Barcelona and western Mediterranean Basin, high insolation, and the development of thermally-driven wind flows. A second regime is characterized by a strong northwestern advection that produced a cleansing action over the atmosphere. And a third identified regime is dominated by strong stagnant conditions produced by thermal inversions that decouple the low troposphere of plain and coastal areas from mountainous terrains. On the other hand, the main meteorological regimes identified for the summer campaign (July 2009) are: a typical summer recirculation pattern, with low pressure gradients over the western Mediterranean basin, high insolation and development of mesoscale features, a second pattern characterized by the advection of southern air masses enriched with mineral dust from North Africa, and a third zonal advective scenario associated with frontal systems that inhibits the mesoscale circulations and leads to some precipitating events over northeastern Spain. Finally, a classification of the main dispersion patterns deduced from backward Lagrangian simulations is presented and discussed. The results help identify the main flow patterns that lead to the formation and accumulation of particulate matter within the boundary layer, and may produce high pollutant concentrations at Montseny or Barcelona sites. During the DAURE winter and summer campaigns, typical meteorological conditions that lead to air pollution episodes of particulate matter within the Western Mediterranean Basin were observed.