Kinga Wałaszek

The impact of precipitation on wet deposition of sulphur and nitrogen compounds

Abstract Atmospheric transport model FRAME has been used in this study to estimate the influence of precipitation on the patterns of wet deposition of oxidised sulphur, oxidised nitrogen and reduced nitrogen in Poland during the years 1981-2005. A constant wind and emission data and year-specific spatially interpolated precipitation data was used in the model. The results show that the correlation coefficient between mean annual precipitation totals and mean wet deposition is above 0.9 for all examined compounds. The spatial patterns of pollutant deposition are similar for all years, with the north-western part of Poland receiving the lowest and the southern, mountainous part, the highest pollutant load. The largest precipitation-induced changes in wet deposition budgets are observed for oxidised sulphur (53% of the average amount between wet and dry year), and smaller for oxidised and reduced nitrogen (30%). Inter-annual precipitation changes cause large variations in the amount of wet deposition of pollutants. This means that the emission abatements may not cause immediate environmental effects, eg reductions in deposition of pollutants and, further ecosystems areas of exceeded critical loads. Abstrakt Model transportu atmosferycznego FRAME został wykorzystany w niniejszej pracy do określenia wpływu opadów atmosferycznych na przestrzenną i czasową zmienność depozycji tlenków siarki, tlenków azotu oraz azotu zredukowanego na obszarze Polski w latach 1981-2005. W modelu zastosowano stałe warunki anemologiczne i emisję oraz mapy rocznych sum opadów uzyskane drogą interpolacji przestrzennej. Wyniki pokazują, że współczynnik korelacji między średnimi rocznymi sumami opadu a średnią mokrej depozycji przekracza 0,9 dla wszystkich analizowanych związków. Schemat przestrzenny depozycji kształtuje się podobnie dla całego okresu, z najniższymi ładunkami zanieczyszczeń w północno-zachodniej części Polski i najwyższymi w górzystej części południowej. Największe zmiany w budżecie depozycji spowodowane zmiennością opadów zachodzą dla tlenków siarki (53% wartości średniej między rokiem suchym i wilgotnym), natomiast słabiej zaznacza się zmienność zarówno dla azotu utlenionego, jak i zredukowanego (30%). Ze względu na to, że zmienność warunków pluwialnych powoduje znaczne wahania mokrej depozycji zanieczyszczeń, ograniczanie emisji może nie spowodować natychmiastowej poprawy dla środowiska, tzn. redukcji depozycji zanieczyszczeń i ograniczenia obszarów o przekroczonych ładunkach krytycznych.

Sensitivity Study of Cloud Cover and Ozone Modeling to Microphysics Parameterization

AbstractCloud cover is a significant meteorological parameter influencing the amount of solar radiation reaching the ground surface, and therefore affecting the formation of photochemical pollutants, most of all tropospheric ozone (O3). Because cloud amount and type in meteorological models are resolved by microphysics schemes, adjusting this parameterization is a major factor determining the accuracy of the results. However, verification of cloud cover simulations based on surface data is difficult and yields significant errors. Current meteorological satellite programs provide many high-resolution cloud products, which can be used to verify numerical models. In this study, the Weather Research and Forecasting model (WRF) has been applied for the area of Poland for an episode of June 17th–July 4th, 2008, when high ground-level ozone concentrations were observed. Four simulations were performed, each with a different microphysics parameterization: Purdue Lin, Eta Ferrier, WRF Single-Moment 6-class, and Morrison Double-Moment scheme. The results were then evaluated based on cloud mask satellite images derived from SEVIRI data. Meteorological variables and O3 concentrations were also evaluated. The results show that the simulation using Morrison Double-Moment microphysics provides the most and Purdue Lin the least accurate information on cloud cover and surface meteorological variables for the selected high ozone episode. Those two configurations were used for WRF-Chem runs, which showed significantly higher O3 concentrations and better model-measurements agreement of the latter.

Evaluation of the WRF meteorological model results during a high ozone episode in SW Poland – the role of model initial conditions

In meteorological, as well as air quality, modelling, input data plays an important role in the accuracy of the results, next to the model configuration. There are many sources of meteorological data available, both global and regional, and they differ not only by spatial and temporal resolution, but also by the number of observations included in the reanalysis and method of data assimilation used. In this study, the performance of the weather research and forecasting (WRF) model with two global reanalyses (ERA-Interim and NCEP FNL) used as input datasets has been assessed for a period of high tropospheric ozone concentrations. Both WRF model runs are in good agreement with observations, with IOA statistic ranging from 0.78 for wind speed to 0.98 for surface pressure. The ERA-Interim simulation showed better results for surface pressure, temperature and wind speed, while the performance of both datasets for parameters related to atmospheric moisture (e.g., dew point temperature) was comparable.

The role of precursor emissions on ground level ozone concentration during summer season in Poland

Three online coupled chemical transport model simulations were analyzed for three summer months of 2015 in Poland. One of them was run with default emission inventory, the other two with NOx and VOC emissions reduced by 30%, respectively. Obtained ozone concentrations were evaluated with data from air quality measurement stations and ozone sensitivity to precursor emissions was estimated by ozone concentration differences between simulations and with the use of indicator ratios. They were calculated based on modeled mixing ratios of ozone, total reactive nitrogen and its components, nitric acid and hydrogen peroxide. The results show that the model overestimates ozone concentrations with the largest errors in the morning and evening, which is primarily related to the way vertical mixing is resolved by the model. Better model performance for ozone is achieved in rural than urban environment, as PBL and mixing mechanisms play more significant role in urban areas. Modeled ozone shows mixed sensitivity to precursor concentrations, similarly to other European regions, but indicator ratios have different values than are found in literature, particularly H2O2/HNO3 is larger than in southern Europe. However, indicator ratios often differ between locations and transition values need to be established individually for a given region.

Application of WRF-Chem to forecasting PM10 concentration over Poland

The meteorological and chemical transport model WRF-Chem was implemented to forecast PM10 concentrations over Poland. WRF-Chem version 3.5 was configured with three one-way nested domains using the GFS meteorological data and the TNO MACC II emissions. The 48 hour forecasts were run for each day of the winter and summer period of 2014 and there is only a small decrease in model performance for winter with respect to forecast lead time. The model in general captures the variability in observed PM10 concentrations for most of the stations. However, for some locations and specific episodes, the model performance is poor and the results cannot yet be used by official authorities. We argue that a higher resolution sector-based emission data will be helpful for this analysis in connection with a focus on planetary boundary layer processes in WRF-Chem and their impact on the initial distribution of emissions on both time and space.

A Sensitivity Analysis of the WRF Model to Shortwave Radiation Schemes for Air Quality Purposes and Evaluation with Observational Data

Shortwave radiation is a key meteorological component influencing formation and destruction of many atmospheric pollutants, most of all tropospheric ozone. It is the main driver of photochemical reactions, affects surface temperature and enhances biogenic VOC production. Because uncertainties in meteorological fields provided by meteorological models highly affect chemical transport model simulations, accurate information on spatial and temporal variability of shortwave radiation is needed for reliable air quality modeling. The main aim of this study is to assess the meteorological model performance in representing observational data. In this study, the Weather Research and Forecasting (WRF) model is applied to the area of Lower Silesia, Poland, in order to test three shortwave radiation schemes: Goddard, RRTMG and GFDL scheme. The test period is a high ozone episode of 17.06-04.07.2008. Simulations were run with different shortwave radiation options, while all other physics parameterizations remained constant. The results were then evaluated based on radiation measurements conducted in the Observatory of the Department of Climatology and Atmosphere Protection in Wroclaw, Poland. There are some discrepancies between the employed parameterizations both in terms of quality of the results and computational costs but in general, all schemes applied show reasonable consistency with observations.

Aerosol-Radiation Feedback and PM 10 Air Concentrations Over Poland

We have implemented the WRF-Chem model version 3.5 over Poland to quantify the direct and indirect feedback effects of aerosols on simulated meteorology and aerosol concentrations. Observations were compared with results from three simulations at high spatial resolutions of 5 × 5 km: (1) BASE—without any aerosol feedback effects; (2) DIR—with direct aerosolradiative effects (3) INDIR—with direct and indirect aerosol-radiative effects. We study the overall effect during January 2011 as well as selected episodes of the highest differences in PM10 concentrations between the three simulations. For the DIR simulation, the decrease in monthly mean incoming solar radiation (SWDOWN) appears for the entire study area. It changes geographically, from about –8.0 to –2.0 W m−2, respectively for the southern and northern parts of the country. The highest changes do not correspond to the highest PM10 concentration. Due to the solar radiation changes, the surface mean monthly temperature (T2) decreases for 96 % of the area of Poland, but not more than 1.0 °C. Monthly mean PBLH changes by more than ±5 m for 53 % of the domain. Locally the differences in PBLH between the DIR and BASE are higher than ± 20 m. Due to the direct effect, for 84 % of the domain, the mean monthly PM10 concentrations increase by up to 1.9 μg m−3. For the INDIR simulation the spatial distribution of changes in incoming solar radiation as well as air temperature is similar to the DIR simulation. The decrease of SWDOWN is noticed for the entire domain and for 23 % of the domain is higher than –5.0 W m−2. The absolute differences of PBLH are slightly higher for INDIR than DIR but similarly distributed spatially. For daily episodes, the differences between the simulations are higher, both for meteorology and PM10 concentrations, and the pattern of changes is usually more complex. The results indicate the potential importance of the aerosol feedback effects on modelled meteorology and PM10 concentrations.

Application of the WRF-Chem Model for Air Pollution Forecasting in Poland

This paper presents the first step in the development of a forecasting system for air pollution concentrations for the south-west region of Poland. We simulated a winter (January) and a summer (July) period of 2014 with WRF-Chem. The focus has been on studying different chemical options during the two simulation periods, therefore keeping emissions constant, except for natural sources. The authors have found that different model setups increase model performance for gases and particulate matter and that there is no clear dependence between forecast lead time and model performance.

Sensitivity of Ground-Level Ozone to NOx Emission During a High Ozone Episode in SW Poland

Sensitivity of ozone formation to NOx and VOC emission is important in terms of implementing control strategies for photochemical pollutants, helping to determine the most effective way to limit O3 concentrations and population exposure to high levels of O3. In this study, the role of NOx emissions on hourly O3 concentrations is examined in order to determine whether NOx is the driver or limiting factor of ozone formation in SW Poland in high-ozone situations. In order to assess that, four scenarios are analyzed: baseline, with no modification of the available emission inventory, a 10, 20 and 30 % decrease in anthropogenic emission of NOx. The simulations were performed for an episode with high O3 concentrations. Both spatial and temporal changes in ozone concentrations for all scenarios have been analyzed. Preliminary results show that reducing NOx emission is associated with higher O3 concentrations, however, further research is needed to assess the role of VOC.

EMEP4PL and WRF-Chem—Evaluation of the Modelling Results

We used two different Eulerian atmospheric transport models—the Weather Research and Forecasting (WRF) coupled online with chemistry (WRF-Chem) and EMEP4PL coupled offline with meteorology from WRF-Chem. The models were run for Poland, which is characterized by a relatively poor air quality, especially during winter seasons. The simulations were run for 2 months—January and July 2015 and modelled concentrations of PM10, PM2.5, SO2 and NO2 were compared with measurements available at a one hour resolution. Both models give better results for the winter period than for summer. For July the WRF-Chem results for particulate matters are improved after inclusion of boundary conditions from the MOZART model. In general WRF-Chem gives higher FAC2 and lower NMB for both months in comparison to EMEP4PL. For EMEP4PL correlations with observations are higher in comparison to WRF-Chem.