Browsing by Subject "Atmosphere"

Now showing 1 - 3 of 3
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    Impact of Pandemic on Atmospheric Carbon
    (2021-08) Mosesov, Eleonora
    The COVID-19 pandemic has caused a decrease in carbon dioxide emissions. Here we will look at the atmospheric carbon dioxide, carbon-13, and carbon dioxide emissions data in order to determine whether the drop in emissions had an effecton atmospheric carbon dioxide and carbon-13. For carbon dioxide and carbon-13, we look at the trend and the seasonal pattern. To find whether 2020 is an outlier, we find the average values and compare them to previous years, as well as compare the monthly data. The data in 2020 for the atmospheric carbon dioxide and carbon-13 did not show a drop, and was not an outlier.
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    Improvement of the Mellor-Yamada Type Planetary Boundary Layer Scheme for Use in Mesoscale Models
    (2020-08) Keester, Adam
    Atmospheric mesoscale models are highly complex and their performance varies widely depending on the models used. Turbulent transport within the boundary layer is especially difficult to analyze, but has a significant impact on mesoscale model applications. In this study, the Mellor-Yamada-Nakanishi-Niino planetary boundary layer model is improved. A new length scale and turbulent closure constants are calculated from two large eddy simulations. The modified MYNN model maintains the original’s accurate eddy coefficients and drastically improves the prediction of the momentum dissipation rate, length scale and stability functions. A 12-member WRF ensemble is used to validate the new model outside of the database on which it is based. The WRF results show that the new model improves the bias and mean absolute error of temperature and relative humidity. There is a significant change in the TKE and length scale predictions that motivates further study of the modified boundary layer scheme.
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    The occurrence and environmental fate of polybrominated diphenyl ethers and glyphosate in the atmosphere.
    (2010-08) Chang, Feng Chih
    The net air-water exchange flux of polybrominated diphenyl ethers (PBDEs) in the Great Lakes and the atmospheric presence of glyphosate and aminomethylphosphonic acid (AMPA) in the farm fields are reported here for the first time. Paired air and surface water samples were collected during May and July from Lake Michigan in 2005 and Lake Superior in 2006. Average atmospheric PBDE concentrations and deposition were higher over Lake Michigan than Lake Superior and higher at nearshore urban than open-lake sites. Additionally, annual mass budgets of PBDEs for the Great Lakes are presented by estimating atmospheric deposition, wastewater treatment plant discharge, burial of lake sediments, and lake water outflow. The results indicated that annual mass budget of "6PBDE (BDE-47, 66, 100, 99, 154, and 153) for Lake Michigan was a net increase with 270 kg yr-1. In contrast, the budget for Lake Superior approached equilibrium with a net increase of 14 kg yr-1. Wet deposition was the major contributor (71-75%) of the total "6PBDE inputs to both lakes. Glyphosate and AMPA were detected only in the particle phase of air samples in Mississippi and Iowa in 2007-2008. The frequency of glyphosate detection ranged from 61 to 100% (in air) and 63 to 92% (in rain). The highest concentrations of glyphosate and AMPA in both air and rain were found during the periods of intense glyphosate applications. Glyphosate and AMPA were removed efficiently from the air by particle scavenging in rainfall events. Based on annual mass budgets of glyphosate in Mississippi and Iowa study sites, less than 0.1% of the applied glyphosate moved into the atmosphere due to application spray drift (0.01%-0.05%), and wind erosion (<0.01%-0.02%).