Differential optical absorption spectroscopy (DOAS) is a useful technique for measuring nitrogen dioxide (NO2) and aerosol, the most important species in urban environmental pollution. This paper reports on the result...Differential optical absorption spectroscopy (DOAS) is a useful technique for measuring nitrogen dioxide (NO2) and aerosol, the most important species in urban environmental pollution. This paper reports on the results of our dual path DOAS measurements recently conducted in Chiba City, Japan, using xenon flashlights equipped on tall constructions as aviation obstruction lights. Because of the proximity of the southern DOAS path to an industrial area, it is found that the level of air pollution generally increases with the dominance of westerly winds, from the plausible source area to the observation light path. This situation is consistent with the result of wind lidar measurement covering a sector of ±28? with the observation range of approximately 2.8 km. In spite of the fact that the two DOAS paths, having path lengths of 5.5 and 3.5 km each, are located in separated regions of Chiba City, the observed temporal behavior was similar for both nitrogen dioxide and aerosol, though the southern path tends to exhibit slightly higher pollution levels than the northern counterpart. Additionally it is confirmed that size information of aerosol particles can be derived from the DOAS data through the analysis of the wavelength dependence of the aerosol optical thickness, which shows fairly good correlation with the mass ratio between PM2.5 and suspended particulate matter (SPM) obtained from the in-situ sampling station measurement. Thus, the DOAS approach can also be utilized for obtaining information on PM2.5 that is considered to be more harmful to human health than SPM.展开更多
Forecasting flooding hazards is a very effective non-engineering measure for flood control.Presently,the commonly used forecasting method in simulating flash flood events is through a watershed hydrological model.Many...Forecasting flooding hazards is a very effective non-engineering measure for flood control.Presently,the commonly used forecasting method in simulating flash flood events is through a watershed hydrological model.Many Asia-Pacific countries like the Philippines are prone to frequent hydrometeorological hazards such as tropical cyclones,resulting in frequent heavy rainfall events.However,most rivers in the many basins lack water flow observation data,which makes it challenging to use lumped and data-driven models for flash flood forecasting.With the continuous progress of remote sensing(RS)and geographic information system(GIS)techniques,the physically-based distributed hydrological model(PBDHMs)has rapidly advanced.PBDHMs can directly determine the model parameters according to the underlying surface characteristics from remotely-sensed data,which makes it possible for flood forecasting in areas with little to virtually no data.In this study,the Matina River basin in Davao City was selected as a case study in simulating a small data-poor basin in the region.The Liuxihe model was used to formulate a forecasting scheme and simulated the past flash flood events.The results show that there is a good correspondence between the past heavy rainfall events and their corresponding simulated river discharges.The results conform to the hydrological regularities,which can be used for flood forecasting and can serve as a baseline for the development of a flood forecasting system in the rivers of Davao City and elsewhere.展开更多
文摘Differential optical absorption spectroscopy (DOAS) is a useful technique for measuring nitrogen dioxide (NO2) and aerosol, the most important species in urban environmental pollution. This paper reports on the results of our dual path DOAS measurements recently conducted in Chiba City, Japan, using xenon flashlights equipped on tall constructions as aviation obstruction lights. Because of the proximity of the southern DOAS path to an industrial area, it is found that the level of air pollution generally increases with the dominance of westerly winds, from the plausible source area to the observation light path. This situation is consistent with the result of wind lidar measurement covering a sector of ±28? with the observation range of approximately 2.8 km. In spite of the fact that the two DOAS paths, having path lengths of 5.5 and 3.5 km each, are located in separated regions of Chiba City, the observed temporal behavior was similar for both nitrogen dioxide and aerosol, though the southern path tends to exhibit slightly higher pollution levels than the northern counterpart. Additionally it is confirmed that size information of aerosol particles can be derived from the DOAS data through the analysis of the wavelength dependence of the aerosol optical thickness, which shows fairly good correlation with the mass ratio between PM2.5 and suspended particulate matter (SPM) obtained from the in-situ sampling station measurement. Thus, the DOAS approach can also be utilized for obtaining information on PM2.5 that is considered to be more harmful to human health than SPM.
基金supported by the Natural Science Foundation of China(No.51961125206)
文摘Forecasting flooding hazards is a very effective non-engineering measure for flood control.Presently,the commonly used forecasting method in simulating flash flood events is through a watershed hydrological model.Many Asia-Pacific countries like the Philippines are prone to frequent hydrometeorological hazards such as tropical cyclones,resulting in frequent heavy rainfall events.However,most rivers in the many basins lack water flow observation data,which makes it challenging to use lumped and data-driven models for flash flood forecasting.With the continuous progress of remote sensing(RS)and geographic information system(GIS)techniques,the physically-based distributed hydrological model(PBDHMs)has rapidly advanced.PBDHMs can directly determine the model parameters according to the underlying surface characteristics from remotely-sensed data,which makes it possible for flood forecasting in areas with little to virtually no data.In this study,the Matina River basin in Davao City was selected as a case study in simulating a small data-poor basin in the region.The Liuxihe model was used to formulate a forecasting scheme and simulated the past flash flood events.The results show that there is a good correspondence between the past heavy rainfall events and their corresponding simulated river discharges.The results conform to the hydrological regularities,which can be used for flood forecasting and can serve as a baseline for the development of a flood forecasting system in the rivers of Davao City and elsewhere.
