Processing categories: point
The Laypoint program uses the SMOKE point-source inventory file with gridded and hourly meteorology data to compute hourly plume rise for all point sources. The plume rise is expressed in terms of layer fractions for each source.
Laypoint is run only for the MAQSIP and CMAQ styles of processing, in which all of the plume rise calculations are done prior to input to the AQM. In Laypoint, meteorological data are used to calculate the plume rise for all point sources. Then, the plume is distributed into the vertical layers that the plume intersects based on the pressure in each layer. Only these fractions are stored (not the emissions in each layer), until the SMOKE merge step (Smkmerge). Therefore, the plume rise calculations do not need to be repeated for each control strategy or grid (unlike the situation in which the plume rise calculations are done inside the AQM, such as in UAM-IV and UAM-V). The Laypoint program calculates the plume rise for all days of each meteorological scenario.
The Briggs solution is documented in the following:
Briggs, Gary A., 1971: Some Recent Analyses of Plume Rise Observation, pp. 1029-1032 in Proceedings of the Second International Clean Air Congress, edited by H. M. Englun and W. T. Beery. Academic Press, New York.
Briggs, Gary A., 1972: Discussion on Chimney Plumes in Neutral and Stable Surroundings, Atmos. Environ. 6, 507-510.
The following formula is used in Elevpoint:
F = 0.25 x G x VS x DS2 x (TS - T)/TS
For F less than 55,
Plume rise = HS + 21.31311057 x F0.75/U
Otherwise,
Plume rise = HS + 38.87776061 x F0.6/U
where
This represents an improved algorithm over the original so that the discontinuity at F = 55 no longer exists. Now, the second term in the plume rise formula approaches 595 as F approaches 55 from either side.