Wind speed averages

Fig. 21-6. Mean annual wind speed averaged through the afternoon mixing layer. Speeds are in meters per second. Source Adapted ftom Holzworth (2).

It should be emphasized that Figure 3.5 presents the mean zonal wind, that is, the wind speed averaged over longitude and time. In addition, local variations in the wind speed and direction are observed. These dynamical disturbances are associated with the presence of atmospheric waves (see Section 3.4). The propagation of these waves through the atmospheric medium is determined by the basic state of the atmospheric fluid at the same time, the dissipation of the waves tends to modify the basic state itself. Beside radiatively forced seasonal variations,... 

Introduction Gas dispersion (or vapor dispersion) is used to determine the consequences of a release of a toxic or flammable material. Typically, the calculations provide an estimate of the area affected and the average vapor concentrations expected. In order to make this determination, one must know the release rate of the gas (or the total quantity released) and the atmospheric conditions (wind speed, time of day, cloud cover). 

What is the steady-state concentrahon derived from the box model for a 10-km city with average emissions of 2 x 10" g m s when the mixing height is 500 m and the wind speed is 4 m s ... 

Using simplified techniques for estimating the concentrations from area sources, what is the annual average particulate matter concentration for a city with an average wind speed of 3.6 m s and area emission rate of 8 x 10 g s m" ... 

Data for one full year (1964) for Nashville, Tennessee, and Knoxville, Tennessee, 265 km (165 mi) apart, were compared to determine the extent to which the frequencies of various parameters were similar. Knoxville is located in an area with mountainous ridges oriented southwest-northeast Nashville is situated in a comparahvely flat area. The data available are the number of hours during which each of 36 wind directions (every 10° azimuth) occurred, the average wind speed for each direction, the number of hours of each Pasquill stability class for each direchon, and the mean annual wind speed. 

Because of the slight difference in average wind speed, one might expect this to cause a greater frequency of both stable and unstable condihons at... 

Since U is a function of z, some mean value must be used. The appropriate value is the mean through the plume. However, the time-averaged wind speed at the stack height is commonly used. Often, even this value may not be known, in which case an estimate must be made. This estimate could be based on an assumed power law velocity profile such as ... 

Atmospheric Conditions - Normal average wind speed, ambient air temperature, air density, relative humidity. 

U. = Normal average wind speed, m/s, based on local meteorological conditions... 

The weather data are based on thousands of observations of wind speed, wind direction and atmospheric stability taken over the desired averaging interval at local weather bureau stations. 

Similar behavior was observed for LNG clouds during both continuous and instantaneous tests, but average flame speeds were lower the maximum speed observed in any of the tests was 10 m/s. Following premixed combustion, the flame burned through the fuel-rich portion of the cloud. This stage of combustion was more evident for continuous spills, where the rate of flame propagation, particularly for LNG spills, was very low. In one of the continuous LNG tests, a wind speed of only 4.5 m/s was sufficient to hold the flame stationary at a point some 65 m from the spill point for almost 1 minute the spill rate was then reduced. 

An estimate is required of the total hydrocarbon concentration 300 meters downwind of an expressway on an overcast day with wind speed 4 m/s. Tlie expressway runs norlli-south and the wind is from tlie west. Tlie measured traffic flow is 8000 vehicles per hour during tlris rush hour, and the average speed of the velucles is 40 mph. At tlris speed tlie average vehicle is expected to... 

Wind turbines produce power by converting the force of the wind into torque. The power produced is a function of the wind energy flux (power), which, in turn, is a function of the air density multiplied by the wind velocity raised to the third power. Changes of air density with time at a particular site are negligible compared to the fluctuations in wind velocity. Meteorologists usually report wind speed as an average. To get the potential wind power, the average... 

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