Rain intensity

Rain Intensity plots for met data files containing precipitation data. 

Color wind rose and rain intensity plots. 

Precipitation both in the form of rain and snow can produce bubbles on the sea (3). Bubbles from moderate rain intensities have diameters of less than 200 /xm, and those produced by snow are less than 100 /xm. However, since these bubbles are produced only in the upper few centimeters of the sea and only during the precipitation, they do not constitute the major source of bubbles in the sea. The precipitation of the continental aerosol into the sea has been suggested as a source of bubbles (50), but since this aerosol is composed of particles primarily less than 100 /xm diameter, and since water drops of 100 /xm diameter produce no bubbles when they fall into the sea (3), it is unlikely that the continental aerosol produces a significant quantity of bubbles. 

Different rainfall weighting methods can substantially affect estimates of new/old waters in storm runoff in basins with large contributions of new water (McDonnell et al., 1990). Use of sequential rain values is probably the best choice in very responsive catchments or in catchments with high proportions of overland flow. When rain intensities are low and soils drain slowly, current rain may not infiltrate very rapidly and thus use of the cumulative approach (i.e., running average) is probably more realistic (Kendall et al., 2001a). 

Fig. 7.14.5 Ratio wiping mode/speed over rain intensity...

During rain, soluble species that exist below clouds dissolve into falling raindrops and are removed from the atmosphere. We would like to estimate the rate of removal of these species based on rain event characteristics (rain intensity, raindrop size) and species physical and chemical properties. 

Let us assume that the rain intensity is po (mmh-1) and all rain droplets have diameter Dp (m). The volume of water deposited per unit surface area will then be 10 3/>o (m3 m-2 h 1). The number of droplets falling per surface area per hour will be equal to 6 x 10 3p0 l -Dp and the rate of wet removal of the material below cloud Fbc will be equal to [using (20.21)]... 

Let us assume that the rain intensity is po (mm h ) and all rain droplets have diameter Dp (m). The volume of water deposited per unit surface area will then be 10 m... 

FIGURE 20.4 Time necessary for the removal of 50% of HNO.i(g) in a homogeneous atmosphere as a function of the rain intensity and the assumed minimum diameter in the Marshall-Palmer distribution used in the calculation. 

The time necessary to remove 50% of the HNOj vapor in a homogeneous atmosphere is shown in Figure 20.4 as a function of the rain intensity for a MP distribution and different assumed minimum droplet sizes. This time can be calculated using (20.24) as... 

To determine the contribution of dry versus wet deposition, Goodwin initiated laboratory tests using synthetic rainfall of different pH values. Dry deposition was attained by setting panels in a louvered box outdoors. Rain intensities between 0 and 12 mm/h were used. This technique made it possible to vary sulfate concentration independently of pH. Rolled pure zinc panels were used for all tests. Atmospheric corrosion rates of zinc is Scandinavia, when only dry deposition was allowed, were measured to be 12 g/m / year based on an exposure period of 2.5 months. Exposure of these dry panels to artificial rainfalls with pH values of 4.5 and 3.5 decreased their corrosion rates. Only when rainfall pH was lowered to 2.5 did zinc corrosion rate increase over that seen with solely dry deposition (Fig. 2.7). 

Rainfall intensity appears to be inversely correlated with insecticide concentration in washoff 60) and concentrations are typically highest in first few millimeters of washoff (57). Lower insecticide concentrations at higher rain intensities may be due to the greater thickness of the water layer on the leaf surface and the shorter residence time of a unit volume of water on the leaf. 

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