Abstract
Within the CO2 time series measured at the Environmental Research Station Schneefernerhaus (UFS), Germany, as part of the Global Atmospheric Watch (GAW) program, pollution episodes are traced back to local and regional emissions, identified by δ13C(CO2) as well as ratios of CO and CH4 to CO2 mixing ratios. Seven episodes of sudden enhancements in the tropospheric CO2 mixing ratio are identified in the measurements of mixing/isotopic ratios during five winter months from October 2012 to February 2013. The short-term CO2 variations are closely correlated with changes in CO and CH4 mixing ratios, achieving mean values of 6.0 ± 0.2 ppb/ppm for CO/CO2 and 6.0 ± 0.1 ppb/ppm for CH4/CO2. The estimated isotopic signature of CO2 sources (δs) ranges between −35‰ and −24‰, with higher values indicating contributions from coal combustion or wood burning, and lower values being the result of natural gas or gasoline. Moving Keeling plots with site-specific data selection criteria are applied to detect these pollution events. Furthermore, the HYSPLIT trajectory model is utilized to identify the trajectories during periods with CO2 peak events. Short trajectories are found covering Western and Central Europe, while clean air masses flow from the Atlantic Ocean and the Arctic Ocean.
Highlights
Since the beginning of the industrial era, atmospheric greenhouse gas (GHG) concentrations have been rapidly increasing due to fossil fuel burning and deforestation [1]
Seven events of high CO2 concentration that occurred within five months at the Environmental Research Station Schneefernerhaus (UFS) were investigated
Regarding the characterization of the detected events, a combination of four types of information—namely, the δ13 Cs signature determined by Keeling plots, carbon monoxide (CO)/CO2 correlation, CH4 /CO2 correlation, and back trajectory analysis using the HYSPLIT mode—was employed
Summary
Since the beginning of the industrial era, atmospheric greenhouse gas (GHG) concentrations have been rapidly increasing due to fossil fuel burning and deforestation [1]. Due to its remote and elevated location, the UFS is relatively less influenced by direct anthropogenic emissions and measurements of background concentrations there can be regarded as representative of a larger region [3,4]. The station is occasionally influenced by local-to-regional emissions due to the air mass transport of polluted boundary layer air and/or local effects. These polluted air masses contain signals from continental sources, as indicated by the high variability in trace gas concentrations on time scales of hours and days [5]. In order to improve the retrieval of atmospheric background CO2 concentrations from measurements at these remote sites, it is crucial to investigate these pollution-affected periods systematically, as well as to identify their source regions
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