7.6 Determining 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 estimate zic.

This is accomplished as follows:

- Determine d2/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 then zic is defined as missing.

- Extend the sounding by persisting d2/dz up and recomputing zic.

- Provide warning messages which tell users

- the height of the actual sounding top,

- that d2/dz has been extrapolated above the sounding zic, and

- that zic has been recomputed.

- Allow the user to reject the “fixed-up” value for zic by defining it as missing.

7.7 Input

7.7 Input 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

7.8 Information Passed by AERMAP to AERMOD

AERMAP passes the following parameters to AERMOD: xr, yr, zr, zt, & the height scale (hc )

for each receptor.

7.9 Wind 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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