ISOTOPIC SIMULATION OF COMBUSTION-DERIVED VAPOR EMISSION IN URBAN AREA USING REGIONAL SPECTRAL MODEL

Abstract

 Anthropogenic water vapor emissions became an important component of the urban atmosphere with the process of urbanization, and one of the main sources of anthropogenic water vapor emissions is the fossil fuel combustion-derived vapor (CDV). Due to the extremely low d-excess value of CDV, stable hydrogen and oxygen isotope can be a promising method to partition CDV from other natural sources. Considering the limitation of in-situ observation, this study explored the possibility to use IsoRSM, an isotopic-enable regional spectral model to simulate the emission situation of CDV in the urban area. A one-month experiment in Salt Lake City and a one-year experiment in Beijing were made respectively. The simulating result indicated that the addition of CDV could significantly decrease the d-excess of water vapor, especially when the boundary layer was stable. The simulation with CDV emission fitted better with the time series of in-situ observation than the simulation without CDV in Salt Lake City. Furthermore, the addition of CDV also resulted in an obvious negative correlation between vapor d-excess and specific humidity. High d-excess in the winter season in Beijing might be caused by other factors such as strong kinetic fractionation in evaporation caused by the hard winter monsoon. In the simulations, the CDV fraction in Salt Lake City could reach more than 13%. The results indicated that the anthropogenic emission could not be ignored particularly in studies on the urban atmospheric hydrological cycle.