Amela Jeričević

The critical bulk Richardson number in urban areas: verification and application in a numerical weather prediction model

Dispersion models require hourly values of the mixing height (H) that indicates the existence and vertical extent of turbulent mixing. Urban areas, which are usually industrial areas too, have H higher than rural areas, and commonly used methods for deriving H should not be applied under the same conditions as in homogeneous conditions. The bulk Richardson number (RiB) methodwas applied to determineH over Zagreb, Croatia. Impact of urban areas on the choice of critical values of bulk Richardson number (RiBc) was explored, and different values were used for convective boundary layer (CBL) and for stable boundary layer (SBL). Aire Limitee Adaptation Dynamique development InterNational (ALADIN), a limited area numerical weather prediction (NWP) model for short-range 48-h forecasts, was used to provide one set of input parameters. Another input set comes from radio soundings. The values of H, modelled and based on compared measurements, and the correlation coefficient as well as standard deviation and bias were calculated on a large data set to determine RiBc ranges applicable in urban areas. It is shown that RiB method can be used in urban areas, and that urban RiBc should have certain limitations despite of a wide spectrum of practical values used today. Significantly increased RiBc values in SBL were determined from the NWP and soundings data, which is the consequence of increased surface roughness in the urban area. The verification of ALADIN through the determination of H was also done. Decoupling from the surface in the very SBL was detected as a consequence of the flow cease resulting in RiB becoming very large.

Modelling of Heavy Metals: Study of Impacts Due to Climate Change

Heavy metals are a category of pollutants recognized as dangerous to human health and human exposure occurs through all environmental media. Since metals are naturally occurring chemicals that do not break down in the environment and can accumulate in soils, water and the sediments of lakes and rivers, it is important to evaluate the contribution of natural emission sources in the environment. Owing to climate change, the water content in soil is decreased while evapotranspiration is increased as a consequence the higher resuspension of soil dust particles. In this work, a modelling study of heavy metals was performed in order to assess the levels of heavy metals pollution, particularly lead, in Croatia and to estimate the effects of an increase in lead natural emissions due to climate change.

Exploring the properties of local and non-local vertical diffusion schemes in the EMEP model using 222 Rn data

The simulations of hourly 222 Rn concentrations are performed with the EMEP model to validate different parameterization schemes for vertical mixing. In addition to recently evaluated non-local vertical diffusion schemes, a new scheme which is a local and based on total turbulent energy (TTE) has been implemented in the model and evaluated. Due to its properties 222 Rn is commonly used to study the model sub-grid mixing schemes, numerical advection schemes or to compare the performance of different models. The effects on simulated 222 Rn concentrations are investigated providing useful information on dynamic properties and on turbulence parameterization techniques.

Influence of WRF Parameterization on Coupled Air Quality Modeling Systems

This study presents the continuation and exploration of the research by application of regional and high resolution air quality (AQ) models. Separate ‘offline’ (WRF—CAMx) and ‘online’ (WRF Chem) coupling modeling systems were used to evaluate the contribution of the local anthropogenic sources over the Republic of Croatia. Within the research with the NWP WRF model, various tests were made with the implementation of the new, improved mixing length scale in MYJ PBL scheme. Default and modified setup of the NWP WRF model was tested on different ABL stability conditions and coupled with AQ models. Experiments with different AQ models also encompassed different time periods with relatively high concentrations in rural and urban areas. Using complex atmospheric chemistry models it was possible to analyze the main processes contributing to the relatively high concentration on regional and local scale and to compare the performance of two different coupling modeling systems.

Air Quality Study of High Ozone Levels in South California

Physical and chemical characteristics within the two distinct meteorological regimes, i.e., convective and stable atmospheric conditions in a complex highly urbanized terrain of the California South Coast Air Basin (CSCAB; the Los Angeles area) were investigated. The Community Multi-scale Air Quality (CMAQ) model was used with a horizontal resolution of 5 km × 5 km to produce the 3D fields of pollutant concentrations. Input meteorological fields were obtained by the MM5 numerical weather prediction model while the input emissions were provided by the Californian Environmental Protection Agency. Modeled meteorological surface parameters and their vertical profiles as well as modeled planetary boundary layer heights (PBL) were compared to the corresponding measurements. The CMAQ simulations of ozone concentrations were compared against the relatively large number of measurements from the CSCAB area. The main goal of the research was to identify the governing atmospheric processes and sources in the coastal area that contributed to the high levels of pollution and to investigate the air quality model’s capabilities to simulate the air quality in the complex topography.