AYBE- İklim ve Deniz Bilimleri Lisansüstü Programı - Doktora

Bu koleksiyon için kalıcı URI

http://hdl.handle.net/11527/267

Gözat

Yazar "Kabataş, Burcu" ile AYBE- İklim ve Deniz Bilimleri Lisansüstü Programı - Doktora'a göz atma
  • Öge
    Sahra Tozunun Doğu Akdeniz Hava Kalitesi Üzerindeki Etkilerinin Atmosfer Modeliyle Belirlenmesi
    (Eurasia Institute of Earth Sciences, 2016-10-04) Kabataş, Burcu ; Ünal, Alper ; 601102002 ; Climate and Marine Sciences ; İklim ve Deniz Bilimleri
    According to the World Health Organization (WHO), air pollution is a major environmental risk to health for urban population in both developed and developing countries and particulate matter (PM) affects more people than any other pollutant. Particles less than 10 micrometers are called PM10, and fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller are called PM2.5. Among sources of particulate matter, mineral dust is one of main contributors of natural aerosol emissions on a global basis contributing around 22% and Sahara is the main contributor to the global dust budget. Epidemiologic studies show that there is a clear link between the dust and adverse health problems such as respiratory diseases, cardiovascular diseases, pulmonary and systemic inflammation. Aside from its effects on human health, transported dust also affects ecosystem by transporting a variety of chemicals and microbial agents (such as bacteria, fungi, and viruses) from source area to other regions. Dust can have both physical and chemical impacts on plants. For instance, it may serve essential nutrients for plant growth such as iron, and phosphorus, yet microbial agents that can be carried thousands of miles in the atmosphere, might be pathogenic to the plants causing rust and other plant disorders. Mineral dust also has a direct role on the radiation budget and regional climate and has a semi-direct effect on cloud cover. Air pollution is one of the major environmental problems in the Mediterranean basin since the limit values of the pollutants are often exceeded. Saharan dust intrusions into the Mediterranean Basin affects 427 million people living in the 21 countries surrounding it. Considering its location, Turkey is downwind of Europe and on the crossroad of long-range dust transport and local emissions, meaning high amount of population living in Turkey are exposed to high PM concentration. The contribution of Saharan dust on PM concentration is still unclear in the Eastern Mediterranean, especially in Western Turkey, where significant industrial sources and metropolitan areas (i.e., Istanbul, Ankara and Izmir) are located. This study aims to quantify the contribution of Saharan dust on high levels of PM10 that was measured in April 2008 via ground observations, satellite data and atmospheric models. Ground observations that is used in this study were obtained from the Turkish Ministry of Environment and Urbanization for the year 2008. Data analysis of the ground observations showed April 2008 had significantly higher values compared to other warm season months with a monthly mean of ~87 μg/m3, where the annual mean PM10 concentration of 2008 was found to be ~82 μg/m3. It is known from the literature that the transition seasons are usually associated with dust transport from Sahara Desert in the Mediterranean Basin. One method to understand the complex nature of aerosol formation is via atmospheric models. In the real atmosphere, both meteorological factors (such as wind speed and direction, turbulence, radiation, clouds, and precipitation) and chemical processes (such as deposition, and transformations) play important roles on air quality and they are coupled. The interaction of meteorological factors on air quality and atmospheric transport of pollutants is well accepted and they can no longer be conducted separate from each other. Within this scope, we utilized the Real-time Air Quality Modeling System (RAQMS), which is an online global aerosol and chemistry assimilation and forecasting system that was run at 2x2 degrees horizontal resolution, to explore the possible effects of Saharan dust on high levels of PM10 measured in Turkey in April 2008. The RAQMS chemical scheme was developed at NASA Langley Research Center, and the aerosol module incorporates the Goddard Ozone Chemistry Aerosol Radiation and Transport (GOCART) mechanism. RAQMS simulates sulfate (SO4-2), dust, black carbon (BC), organic carbon (OC) and sea-salt aerosols that are known as the major tropospheric aerosol components. The model results showed that the high levels of PM10 observed for April 2008 are related to a Saharan dust outbreak. Due to its coarse resolution (2x2 degree) and inability to resolve local topographic variations, RAQMS was found to over predict the surface PM10 concentration over Turkey by up to a factor of 5. Continuation of the RAQMS research, the higher resolution (30km outer and 10 km nested domains) online-coupled regional Weather Research and Forecasting/Chemistry model (WRF-Chem), a version of the non-hydrostatic model WRF, was utilized. In order to include dust transport from North Africa through lateral boundary conditions (LBC), 6 hourly RAQMS 2x2 degree global analyses was used for 30km run. For background aerosol, GOCART simple aerosol module within the WRF-chem is used. For anthropogenic emissions, two different emission inventories are used, 1×1 degree spatial resolution RETRO (REanalysis of the TROpospheric)/EDGAR (Emission Database for Global Atmospheric Research) and 0.1×0.1 degree spatial resolution EDGAR HTAP (EDGAR: Emission Database for Global Atmospheric Research of the Joint Research Centre, JRC, in cooperation with the Task Force on Hemispheric Transport of Air Pollution (TF HTAP)), to investigate the spatial and temporal distribution of Saharan mineral dust transport over the Eastern Mediterranean (-10.0 W–60.0 E, 30.0 S–70.0 N) for the same time period. The WRF-Chem results were found to be significantly improved compared to the previous RAQMS study. WRF-Chem HTAP outer and nest domain were able to more accurately resolve local emissions that influence the ground observations than the WRF-Chem EDGAR run. The comparison between ground observations to the WRF-Chem HTAP model predictions indicated that the model was able to simulate dust transport patterns and the concentrations in a successful way. Followed by WRF-Chem study, we investigated the impacts of satellite data assimilation through assimilation of the Moderate Resolution Imaging Spectroradiometer (MODIS (collection 6)) total aerosol optical depth (AOD) retrieval products (at 550 nm wavelength) from Terra satellite within the National Centers for Environmental Prediction (NCEP) Gridpoint Statistical Interpolation (GSI) three-dimensional variational (3DVAR) data assimilation system by using the same configuration that was used for WRF-Chem experiment. The simple GOCART aerosol module that is implemented in WRF-Chem modeling system was used to assimilate 3-D mass concentration of 14 aerosol variables within the model including hydrophilic and hydrophobic components of atmospheric aerosols such as sea salt, dust, organic carbon (OC), black carbon (BC), and sulfate. Two nested domain (10km) experiments were designed to evaluate the impact of AOD DA on predicted PM10 concentrations over Turkey by using the same LBC obtained from 30km domain. Both 10km experiments used the same physical and chemistry options, but one experiment did not employ DA (10km_NoAssim) and the other employed 3DVAR DA (10km_Assim) that updated the 14 aerosol profiles of GOCART aerosol module. When we compared average model outputs with the observation means, we found that both 10km (10km_NoAssim and 10km_Assim) analyses show higher level of variability in the PM10 values compared to 30km_Assim run. Among the 10km runs though, 10km_NoAssim run showed higher level of variability than the 10km_Assim run. So, assimilation lowers the variability especially for the days when high dust event occurred. Daily comparison of surface PM10 measurements to model outputs showed that higher resolution domains (10km_Assim and 10km_NoAssim) overestimate daily surface mean PM10 values more than lower resolution domain (30km_Assim) does for the high dust event days. In order to explore differences in aerosol AOD assimilation between the high resolution domain (10km) and the 30km runs, we have interpolated 30km_Assim run to the 10km grid. Based on the PM10 differences averaged over the surface sites for 30km runs and 10km runs, April 1 and April 13, 2008 are chosen in order to further explore the consistency of the aerosol assimilation at 30 and 10km resolution. On April 1st low dust event day, over the central Anatolia, within the higher resolution domain, the predictions tend to increase due to the 30km_Assim domain influence through the LBC. This increase in higher resolution domain is corrected by employing assimilation by moving the predictions towards the observations. For the eastern part of the domain on April 1, the impacts of assimilation are similar for the 30 and 10km experiments indicating LBC impact is small. On April 13th, when dust is the dominant aerosol, 30km_Assim run shows higher PM10 concentrations than the 30km_Control run. The local emissions, as well as LBC from the 30km domain, add additional enhancements to 10km domain resulting an overestimation in 10km_NoAssim domain (due the large negative differences between 30km_Assim and 10km_NoAssim). Relatively small differences between the two 10km domains again shows that assimilation tends to move the 10km predictions closer to the surface observations during this high dust event. This demonstrates that, in our study, although the nested domains tend to over predict the PM10 concentrations comparing to the 30km domain, assimilation of satellite AOD retrievals moves the model forecasts towards the surface observations within the 10km resolution domains especially on high dust event days.