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Natalie Darrin

FIGURE 4.1 Example of wind rose for a designated period of time, by month, season, or year. The positions of the spokes show the direction from which the wind was blowing. The total length of the spoke is the percentage of time, for the reporting period, that the wind was blowing from that direction. The length of the segments into which each spoke is divided is the percentage of time the wind was blowing from that direction at the indicated speed in miles per hour. Horizontal wind speed and direction can vary with height.

FIGURE 4.1 Example of wind rose for a designated period of time, by month, season, or year. The positions of the spokes show the direction from which the wind was blowing. The total length of the spoke is the percentage of time, for the reporting period, that the wind was blowing from that direction. The length of the segments into which each spoke is divided is the percentage of time the wind was blowing from that direction at the indicated speed in miles per hour. Horizontal wind speed and direction can vary with height.

determination of the area most adversely affected by an emission. Although an area may be located in the most frequently occurring downwind direction from a source, the wind speeds associated with this direction may be quite high so that resulting pollutant concentrations will be low as compared to another direction occurring less frequently but with lower wind speeds.

Smaller in scale than the tertiary circulation mentioned, there is a scale of air motion that is extremely significant in the dispersion of pollutants. This is referred to as the micrometeorological scale and consists of the very short term, on the order of seconds and minutes, fluctuations in speed and direction. As opposed to the "organized" circulations discussed previously, these air motions are rapid and random and constitute the wind characteristic called turbulence. The turbulent nature of the wind is readily evident upon watching the rapid movements of a wind vane. These air motions provide the most effective mechanism for the dispersion or dilution of a cloud or plume of pollutants. The turbulent fluctuations occur in both the horizontal and vertical directions. The dispersive effect of fluctuations in horizontal wind direction is shown graphically in Figure 4.2b.

336 AIR POLLUTION AND NOISE CONTROL v = 1 meter per second ->•

v = 4 meters per second

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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