Snow and rain events

The SCM is freed for other tasks, communication between the process drivers and the SCM is reduced to those instances which only a personal dialog can clear up, despite efficient electronic connections, such as e.g. the following unforeseeable so-called snow and rain events . 

there are practical minded individuals who have the impression that all of this resource harmonization will not accomplish much. As they see it, unforeseeable circumstances will always throw the best harmonization out of the window. This is where we have to be careful not to throw out the baby with the bath water. 

Ask yourself What events within the company are truly unforeseeable and fateful, like snow and rain  

Among them are tool breakage, power outages, an above average quota of absences due to illness, an otherwise reliable supplier fails to deliver on time and does not contact you, etc. 

Take a guess yourself What percentage of all disruptions which appointed and self-appointed deadline chasers mn after day in and day out are attributable to these fated events  

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In an enterprise that has no backlog or bottlenecks, snow and rain events do not matter any more. 

Because of the highly variable nature of precipitation events, quantitatively estimating wet deposition of pollutants is difficult. In addition to meteorological factors, parameters such as the solubility of the pollutant in ice, snow, and rain and how this varies with temperature and pH, the size of the water droplets, and the number present must also be considered for example, snow may scavenge some species more efficiently than rain. 

First of all, there are very few of these events. And second, they occur in a harmonized environment and can be brought under control fast and reliably. And third, the SCM always makes up for these delays if the snow or rain event does not occur just at the end of the business process - e.g. during loading. The longer the remaining net supply chain is, the greater is the SCM s chance to make up for lost time. 

Wet deposition is the rate at which PCBs are removed by precipitation events, including rain, snow and fog. Precipitation removes vapour-phase PCBs by... 

Nitrate Concentrations. The higher concentrations of N03- found in snow than in winter rains have been attributed to higher scavenging of HN03 in the air by snowflakes than by raindrops (4,5,6). Another possibility will be considered here that concentration differences can be explained based on precipitation depth. Concentrations of ions such as S04-- and N03- in precipitation have been shown to vary inversely with precipitation depth (8). During the winter periods considered in this paper, the average precipitation depth for winter rain events was 1.3 cm compared to 0.42 cm (as water equivalent) for snow events. The effect of this difference is shown in Table II... 

A multiple regression analysis was also performed to determine the effect of precipitation depth and precipitation type (snow vs. rain) on the N03- concentration. Cloud temperature was used as a measure of precipitation type and was calculated as described in the next section. Although N03- concentrations were found to be inversely correlated with precipitation volume, there was no significant correlation between N03- concentrations and temperature. Therefore, at this location, the lower water content of snow events... 

S0A- - Concentrations. Based on Tables I and II, there can be no doubt that S04-- levels in winter rain are far higher than in snow at this location, despite differences in precipitation depth. Two possible sources of the difference are the following higher ambient S02 and S04-- concentrations available for scavenging during rain events or higher S02 to S04-- conversion during rain events. These possibilities will be considered further. 

Snowmelt also varies in isotopic composition during the melt period and is commonly different from that of melted snow cores (Hooper and Shoemaker, 1986 Stickler, 1987 Taylor et al., 2001). Part of the changes in snowmelt isotopic composition can be attributed to distinct isotopic layers in the snow, rain events on snow, and isotopic fractionation during melting. In general, the snowmelt has low values early in the season but the 5 0 values become progressively higher as the pack melts (Shanley et al., 2001 Taylor et al., 2001). 

The total number of the precipitations over the year was 52, with 43 rain events and 9 snow events. A total rain column of 405 mm from May 2003 to May 2004 was measured. The monthly mean values of the pH and H concentrations of rain given by a mean of the number of rain events are presented in Table 1. 

All analyses of elevation bins below 2400 m indicate a strong elevational component to SWE accumulation, indicating that lower elevation snow losses are probably a result of warmer winter temperatures and rain-on-snow events. Increased April 1 and maximum SWE values at higher elevations suggest increased precipitation in these areas. This could be the result of warmer air masses having higher moisture contents. 

Deposition is the atmospheric removal process by which gaseous and particulate contaminants are transferred from the atmosphere to surface receptors - soil, vegetation, and surface waters (22,27,28, 32). This process has been conveniently separated into two categories dry and wet deposition. Dry deposition is a direct transfer process that removes contaminants from the atmosphere without the intervention of precipitation, and therefore may occur continuously. Wet deposition involves the removal of contaminants from the atmosphere in an aqueous form and is therefore dependent on the precipitation events of rain, snow, or fog. 

Figure 16. Outflow chemistry from two snowmelt seasons (1986 and 1987) at Emerald Lake, a high-elevation lake in the Sierra Nevada Mountains of California. Maximum N03 concentrations are coincident with ANC minima during the early stages of snowmelt in 1986 and with a rain-on-snow event in 1987. Nitrate episodes are smaller in magnitude than at sites in the eastern United States, hut western lakes may he more susceptible to episodic acidification because they have a lower baseline acid-neutralizing capacity than most eastern lakes. (Reproduced with permission from reference 180. Copyright 1991 American Geophysical Union.)...

Gas- and particle-phase PCBs, PCDDs and PCDFs can be removed from the troposphere by wet and dry deposition.71,72,76,77 Wet deposition refers to the removal of the chemical (or particle-associated chemical) from the atmosphere by precipitation events (through the precipitation of rain, fog or snow to the Earth s surface), while dry deposition refers to the removal of the chemical or particle-... 

Four years of winter precipitation events were analyzed in terms of S04-- and N03- concentrations to provide information on the mechanisms by which these ions are incorporated into precipitation. N03-was higher in snow than in winter rain, as suggested by other studies. However, in this study the difference could be attributed to the lower precipitation depths associated with snows than with winter rains. There was no evidence that snow scavenged HN03 more efficiently than rain at this location. 

Sometimes it is obvious that the two-component model is inadequate rain combined with glacial meltwater (Behrens et at, 1979), for example. For rain-on-snow events where snow cores are used to assess the new-water composition, a two-component model is also inadequate (Wallis et al., 1979). However, if the catchment is snow-covered, overland flow is minimal, the surface area of the stream is small, and several snowmelt lysimeters are used to catch sequential samples of new water derived from infiltration of both rain and melting snow, a two-component model may be sufficient. It is difficult to judge a priori when the isotopic difference between soil water and groundwater is sufficient to require a three-component model (Kennedy et al., 1986 DeWalle et al., 1988 Swistock et al., 1989 Hinton et al., 1994). 

The "new water component. The isotopic composition of rain and snow can vary both spatially and temporally during storms. In general, rain becomes progressively more depleted in and H during an event because these isotopes preferentially rain out early in the storm. Successive frontal and convective storms may have more complex isotopic variations. Intrastorm rainfall compositions have been observed to vary by as much as 90%o in 6 H at the Maimai watershed in New Zealand (McDonnell et al., 1990), 16%o in 5 0 in Pennsylvania, USA (Pionke and DeWalle, 1992) and 15%o in 5 0 in Georgia, USA (Kendall, 1993). 

Selenium compounds released to the atmosphere can be removed from it by dry or wet deposition to soils or to surface water. The annual wet deposition rate of selenium at two rural/agricultural sites in Queenstown, Maryland and St. Mary s, Maryland were 287 and 140 pg/nr-year. respectively (Scudlark et al. 1994). Selenium concentrations ranging from 0.04 to 1.4 pg/L have been detected in rain and snow (Hashimoto and Winchester 1967). Kubota and coworkers (1975) reported selenium concentrations of 0.02-0.37 pg/L in rainwater at several locations in the United States and Denmark. Selenium was detected at average concentrations of 5.60-7.86 pg/L during four rainfall events in Riyadh, Saudi Arabia (Alabdula aly and Khan 2000). 

Wet deposition encompasses the removal of gases and particles from the atmosphere by precipitation events, through incorporation into rain, snow, cloud, and fog water, followed by precipitation (Hales, 1986). As in the case of dry deposition, wet deposition is a complex phenomenon which in this particular case involves transport to the surface of a droplet, absorption, and possible aqueous-phase chemical conversion. Wet removal of gases is frequently approximated by assuming that the species is in equilibrium between the gas and aqueous phases. The equilibrium partitioning is represented in terms of a washout ratio, Wg = [C]drop/[C]air, where [C]drop and [C]ajr are the concentrations of the chemical in the aqueous and gas phases (Mackay, 1991). 

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