7.6Determining The Mixing Height When the Sounding Is Too Shallow
The left hand side of eq. (22) is determined from the morning temperature sounding and the
right hand side from the daytime history of surface heat flux. When the temperature sounding,
obtained from the NWS, does not reach a height which is greater than the convective mixing
height, we must assume a profile for the potential temperature gradient in order to estimatezic.
This is accomplished as follows:
- Determined2/dz in the top 500 m layer of the sounding. However, if part of the 500 m
layer is within the first 100 m of the PBL, the layer should be reduced (to a minimum
thickness of 250 m) to avoid using the portion of the sounding that is below 100 m. If the
above conditions can not be satisfied thenzic is defined as missing.
- Extend the sounding by persistingd2/dz up and recomputing zic.
- Provide warning messages which tell users
- the height of the actual sounding top,
- thatd2/dz has been extrapolated above the sounding zic, and
- thatzic has been recomputed.
- Allow the user to reject the “fixed-up” value forzic by defining it as missing.
7.7Input Data Needs for AERMAP
The following data is required input for AERMAP
- DEM formatted terrain data (xt, yt, zt )
- Design of receptor grid; AERMAP accepts either polar, Cartesian or discrete receptors
7.8Information Passed by AERMAP to AERMOD
AERMAP passes the following parameters to AERMOD:xr, yr, zr, zt, & the height scale (hc )
for each receptor.
7.9Wind Speed & Turbulence Limits Used in Model Calculations
When calculating the effective parameters limits are placed on the such that:
These limits are also applied when selecting the turbulence for plume rise calculations.
Dilution of the plume is determined by the wind that corresponds to the average over the
magnitudes of the wind vectors during a given time interval. But measurements only give the
vector averaged wind, which can be zero, even though the dilution wind is not zero. We can
estimate the dilution wind by assuming that the vector wind,uv, can be expressed as
n1001 - n1002 - n1003 - n1004 - n1005 - n1006 - n1007 - n1008 - n1009 - n1010 - n1011 - n1012 - n1013 - n1014 - n1015 - n1016 - n1017 - n1018 - n1019 - n1020 - n1021 - n1022 - n1023 - n1024 - n1025 - n1026 - n1027 - n1028 - n1029 - n1030 - n1031 - n1032 - n1033 - n1034 - n1035 - n1036 - n1037 - n1038 - n1039 - n1040 - n1041 - n1042 - n1043 - n1044 - n1045 - n1046 - n1047 - n1048 - n1049 - n1050
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