Urban air pollution is of major concern in Spain and also throughout Europe and globally with numerous effects on human health and ecosystems. Since air quality (AQ) is predominantly a problem for human health and the environment, the lowest levels of the atmosphere are the most important to investigate, mainly the planetary boundary-layer (PBL). Atmospheric variables (i.e. temperature, humidity, winds) in the PBL are critically important as inputs for accurate simulations in AQ models. From a modeling standpoint PBL height can be extremely difficult to compute accurately due to the fact that boundary layer processes occur at smaller geographical scales than mesoscale meteorological models can resolve. To that end, atmospheric models make use of parameterizations to represent the boundary layer structure in the lower atmosphere.

This research project aims to evaluate the sensitivity of high-resolution AQ simulations from the CALIOPE AQ forecast system (www.bsc.es/caliope) in the distribution of gaseous photochemical pollutants and particulate matter over Europe using different PBL schemes in the Weather Research and Forecasting (WRF) model. The early stages of the project will focus on the Iberian Peninsula, then a geographical expansion to include the European domain will occur in the latter stage. To accomplish this goal, the project is separated into 3 main activities.First, is to evaluate available methods of calculating PBL height from lidar measurements from the European Aerosol Research Lidar Network (EARLINET, Figure 1) over 4 sites in Spain and Portugal for a continuous 72-hr observational campaign in July 2012. Lidar-determined PBL heights will be compared with those obtained from radiosoundings using the bulk Richardson number technique and the parcel method. An analysis of spatial patterns and temporal evolution of the PBL height will be conducted.

In the second activity, the most significant PBL schemes from the WRF Advanced Research WRF (WRF-ARW) v3.5 model will be determined when compared with lidar-derived PBL heights. WRF-ARW allows the choice between 10 different PBL schemes, each with unique turbulent kinetic energy (TKE) closure. It's critically important to diagnose the PBL correctly in order to achieve reliable AQ simulations.

In the final activity, PBL schemes from the WRF-ARW model will be evaluated in CALIOPE AQ simulations for sensitivity of AQ forecasts (Figure 2) as compared with surface observations from ground AQ stations and satellite-based retrievals from the OMI (Ozone Monitoring Instrument) and AIRS (Atmospheric Infrared Sounder) instruments. The expected outcome from this project will be a greater knowledge of the sensitivity of AQ simulations to model PBL schemes, which may result in more accurate operational AQ forecasts.