Study on the long distance transportation of acid snow and its effect on runoff processes

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In the project, study on the acid snow in the northern part of the Lake BIWA has been done. In the study, transportation, reaction and deposition processes are modeled both physically and chemically. Then the cloud microphysics model that considers the chemical processes of acid snow has been developed. We verify the models by comparison with water quality observation. We also developed the model of runoff process which consists of snow fall, snow storage, snow melt, penetration processes. Finally we also verify the model by comparison with observed data.Development of the numerical model of acid snow : Cloud numerical model that includes the explicit type cloud microphysical processes has been developed based on cloud model made by Oishi. Then we consider the generation and deposition processes of SOx and NOx diagnostically. We obtained the result that the mixing ratio of SOx and NOx is quite bigger than observed data. Therefore, we are now in process of development of the model which prognosticate the chemical transportation processes. This model is one of the best models in the world since it can calculate the distribution of cloud droplet diameter that is very important factor for chemical processes.Modeling of Acid snow runoff process and its application to basin scale : We had the important observation period and routine measuring system in very small basin (5.4 Km^2) for making the model of acid snow runoff process. Then we made the application of the models for considering a basin scale by using a water quantity model, a water quality model, a hybrid model and a multi layer model. We obtained the result that the daily variation of snow melting, decreasing of pH by acid shock, daily variation of pH in the river is well explained.