AN APPLICATION OF CALPUFF DISPERSION MODEL TO A NON-STANDARD PROBLEM
Pulp and paper mill situated in the complex terrain of northern Slovakia, in the close vicinity of the city of Ružomberok, continuously releases to atmosphere 30 kg of water vapor per second. Impressive clouds above the industrial complex have given rise to concerns from the side of local citizens, suspecting the emissions to be responsible for the local increase in precipitation. Therefore, a complex study has been initiated, including model simulation of the dispersion of water vapor from the paper mill focused on the domain of 8 x 7 km in close vicinity of the paper mill. Phase conversions of water vapor in the atmosphere are a complex thermodynamic process involving many factors. However, we found out that for some practical applications a simplified approach is sufficient to assess the magnitude of the above mentioned effects. A combination of CALMET-CALPUFF models were applied to compute hourly concentrations of water vapor added to the atmosphere by emissions from the paper mill; these were compared to the hourly absolute humidity values as measured by the meteorological stations in the region, which are not supposed to be affected by the paper mill. The interest was focused on those hours in which the “background” absolute humidity was below saturation value, but additional vapor from the paper mill would bring the value to or above the saturation point. Winter periods of two years (2005, 2006) were modeled and analyzed, during which 66 hours occurred when the additional water from the paper mill caused the humidity to exceed the saturation point, compared to 478 hours with 100% background relative humidity, when the additional vapor from the mill could possibly strengthen the icing effect which would occur anyway. The study concludes that the contribution of the paper mill to total precipitation is negligible even in the close vicinity of the factory. However, in certain cases it can cause icings on a nearby E50 road communication; although these cases are not frequent, they can lead to fatal outcomes. The uncertainties associated with the study method are also discussed.
Cloud Condensation Nuclei from a Paper Mill. Part I: Measured Effects on Clouds
Abstract The effluents from a large Kraft-process paper mill were found to increase the concentration of large (0.2–2 μm diameter) and giant (>2 μm diameter) cloud condensation nuclei (CCN) above background concentrations; the concentrations of small (<0.2 μm diameter) CCN, however, were not increased significantly. Small, nonraining, warm cumulus clouds located in the plume of the paper mill were found to contain higher concentrations of droplets ≥30 μm diameter than similar clouds located outside of the plume; the clouds in both locations contained similar concentrations of droplets ≥5 μm diameter. Cloud droplet size distributions calculated using the CCN measurements are consistent with the measured droplet size distributions. It is concluded that the large and giant CCN from the paper mill increased the concentrations of droplets ≥30 μm diameter in clouds located in its plume. Furthermore, the clouds located in and out of the plume contained similar concentrations of droplets ≥5 μm diameter because th...
The possible influence of urban surfaces on rainfall development: a sensitivity study in 2D in the meso-γ-scale
Urban areas can represent a considerable part of the model domain in meso-scale numerical simulations with typical horizontal domain lengths of 20–200 km. This paper addresses the question of the extent of the influence of urban surfaces on the development of convective precipitation in meso-γ-scale numerical models. For this purpose, a spatially variable parameterization scheme for surface sensible heat flux, surface latent heat flux, and roughness is introduced into a meso-scale numerical model. A sensitivity study in 2D is performed to assess the impact of variations of the individual parameters on the development of precipitation. The results indicate that surface conditions should not be neglected and can have considerable influence on convective rainfall. It appears that within a time frame of 4 h it is particularly the sensible heat flux variations that have the most significant impact.