Precipitation intensity

Surface runoff. Hydrologists have identified two processes for generating surface runoff over land. The first, saturated overland flow (SOF), is generated when precipitation (or snowmelt) occurs over a saturated soil since water has nowhere to infiltrate, it then runs off over land. SOF typically occurs only in humid environments or where the water table rises to intersect with a stream. Horton overland flow (HOF or infiltration-limited overland flow) occurs when precipitation intensity exceeds the infiltration capacity of the soil in a non-saturated environment. In this case, only the excess precipitation (that exceeding the infiltration capacity) runs off over the surface. Both types of overland runoff generate relatively rapid flows that constitute the surface water contribution to the hydrograph (Fig. 6-6). 

Fig. 1 Time series of precipitation intensity (mean wet-day precipitation in mm/ d) from 38 stations in northern Switzerland during the winter. The blue curve denotes the lower and upper quantile of the station values. The bold line depicts the low-pass filtered (11-point binomial filter) median of all station values. Trends (denoted by the straight red line) are estimated from the time series of medians in the station pool. Figure from [13]...

As an approximation, the rate of wet deposition of a pollutant is sometimes taken as AC, where C is the pollutant concentration and A is known as a washout coefficient which is proportional to the precipitation intensity (Shaw, 1984). 

During the 20th century, precipitation intensity increased by 0.5%—1%/10 years over most land regions in NH middle and high latitudes. 

Precipitation intensity decreased by about 0.3%/10 years over most land in sub-tropical latitudes, and quite recently it decreased. 

Answer 2.4 To assess recharge we also need the range of annual precipitation intensities or the variance. There are reports of recharge in arid areas that is sustained by once-in-a-decade heavy rain events. This is an example of the problems that are connected with the selection of single representative parametric values—they cannot adequately describe an entire system. 

It is well known that, after its absorption, NOz forms nitric acid and nitrous acid in water. There is some indication that nitrite produced in this way is oxidized by dissolved 03 (Penkett, 1972). If neutralizing agents (ammonia, calcium carbonate etc.) are present, some nitrate salt is finally formed. It follows from this discussion that both S02 and N02 are oxidized in cloud water by atmospheric ozone. If this speculation is true a correlation should be found between the concentration of sulfate and nitrate ions in precipitation waters. Such a correlation was found in precipitation samples by Gambell and Fisher (1964) among others. However, correlations between any two species in rainwater must be considered with caution because the level of all ions is affected in a similar way by the precipitation intensity or quantity (see Subsection 5.4.1). Nevertheless the identical annual variations of the two ions in precipitation water (see Subsection 5.4.5) suggests that the two species are formed by some similar processes. 

Average variation of calcium and ammonium concentration in precipitation samples (solid lines) as a function of the duration (expressed in %) of rainfall. Dashed line is the precipitation intensity... 

On the basis of our foregoing discussion, the pattern represented by Fig. 44 may be explained as follows. Let us consider a cloud with precipitation which moves over our sampling site. At the beginning, precipitation elements fall from the frontal part of the cloud. In this part, near the edge of the cloud, the liquid water content is low and consequently the water is more concentrated. Since there is a direct relation between liquid water content in the cloud and precipitation intensity at the surface the rainfall rate is also low at this time. The light rain falls in an unwashed polluted atmosphere which is frequently unsaturated with water vapour. Both circumstances... 

Power-law distiibiition, A26-A2E Precipitation intensity, 1005, 1018 Precipitation scavenging of gases, 1003-1016 ofpaiticles, 1016-1026 rates, 1021-1026... 

Climate and weather are closely related and both are believed to influence debris flow activity. The influence of rainfall has already been discussed and tends to be of immediate concern on the short term time scale over which debris flows occur. Because climate describes average weather over a long period of time it is not always considered as a factor in the analysis of debris flow occurrence. Climatic factors that are likely to influence debris-flow initiation are seasonality of precipitation, storm types, and dominant storm tracks (Wilson, 1997, Wilson, R.C., 1997). Other climatic factors that should also be considered are water budget, record rainfall for any recorded storm, maximum observed precipitation intensity, and average wind direction. 

Mechanisms for updating of the hazard analysis with reference to very fast modifications in the intrinsic properties relating to both precipitation (intensity, area and frequency) and the basin (drainage, population, water storage and artificial obstacles). 

Fig. 77.3 Average annual precipitation compared to precipitation intensity, UK and eastern US. Note that while averages are similar, intensities are much greater in the US...

Fig. 8.15(b) contains aU swelling data obtained on the CASTOR 316Ti samples having a classical low phosphoms content and irradiated to 71 dpa/450°C. To illustrate the Ti-stabUization effect, these data have been normalized to the swelling obtained under the same conditions on cold worked 316 with a similar composition except in Ti. These measurements are reported herein as a function of the stabilization ratio SR = (Ti + Nb + V)/C (in which the compositions are expressed in % by atom) that determines the available quantity of C and Ti in solution and the carbide precipitation intensity, rather than as a function of the only Ti content. 

Precipitation data (i.e., volume of precipitation per unit of time) are also required to enable the design of the drainage system of the reclamation area. For the design both peak precipitation intensity and average annual or seasonal values must be known. 

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