Heterogeneous ice nucleating particle (INP) concentrations are reported for a site on the eastern margin of Beijing, China, during the period 4 May to 4 June 2018. INP concentrations were measured continuously at −20, −25, and −30 °C in a repeating cycle by a newly developed, automated continuous flow diffusion chamber, and reached concentrations as high as 2800 sL−1 during dust‐impacted periods. Study average concentrations were 70 ± 70, 230 ± 290, and 430 ± 500 sL−1 at −20, −25, and −30 °C. There was no clear relationship between pollution periods, identified based on fine‐mode particle concentration increases, and INP concentrations or characteristics. Other anthropogenic emissions, such as non‐combustion industrial or agricultural activities play an unresolved role.

Abstract. In this paper, we use the Hydrologic Modeling System (HEC-HMS) to simulate two flood events to investigate the effect of watershed subdivision in terms of performance, the calibrated parameter values, the description of hydrologic processes, and the subsequent interpretation of water balance components. We use Stage IV hourly NEXRAD precipitation as the meteorological input for ten model configurations with variable sub-basin sizes. Model parameters are automatically optimized to fit the observed data. The strategy is implemented in Clear Creek Watershed (CCW), which is located in the upper Mississippi River basin. Results show that most of the calibrated parameter values are sensitive to the basin partition scheme and that the relative relevance of physical processes, described by the model, change depending on watershed subdivision. In particular, our results show that parameters derived from different model implementations attribute losses in the system to completely different physical phenomena without a notable effect on the model's performance. Our work adds to the body of evidence demonstrating that automatically calibrated parameters in hydrological models can lead to an incorrect prescription of the internal dynamics of runoff production and transport. Furthermore, it demonstrates that model implementation adds a new dimension to the problem of non-uniqueness in hydrological models.