Using Profiles for Interpolating Between Observations
When observations are available AERMOD uses the similarity profile functions to interpolate adjacent measurements. Figure 17 illustrates how AERMOD’s INTERFACE uses the expected shape of a meteorological profile to interpolate between observations..103
Figure 17: AERMOD’s
construction of a continuous meteorological profiles by interpolating
between observations.
For a gridded profile height between two observed profile heights, the observations are interpolated to the gridded height while maintaining the shape of the similarity profile. This is accomplished as follows:
1. The observations are linearly interpolated to the gridded profile height;
2. The similarity function is evaluated at the gridded profile height;
3. The similarity function is evaluated at the observed profile heights immediately above and below the grid height and linearly interpolated to the grid height;.104
4. The ratio of the value obtained in 2 to the value obtained in 3 is applied to the value obtained in 1.
For a gridded profile height above the highest observation, the procedure is modified slightly:
1. the observation at the highest observed profile height is extrapolated by persisting the value upward;
2. The similarity function is evaluated at the grid height;
3. The similarity function is evaluated at the highest height in the observed profile;
4. The ratio of the value obtained in 2 to the value obtained in 3 is applied to the value obtained in 1.
A similar procedure for extrapolating to heights above the observed profile is applied to heights below the lowest observed profile height.
8 APPENDIX: Input / Output Needs and Data Usage
8.1
AERMET Input Data Needs
8.1.1
METEOROLOGY
8.1.2
DIRECTIONALLY AND/OR MONTHLY VARYING SURFACE
CHARACTERISTICS
8.1.3
OTHER
8.1.4
OPTIONAL
8.2
Estimation of solar insolation for small solar elevation angles
8.3
Selection and Use of Measured Winds,
Temperature and Turbulence in AERMET
8.3.1
THRESHOLD WIND SPEED
8.3.2
REFERENCE TEMPERATURE AND HEIGHT
8.3.3
REFERENCE WIND SPEED AND HEIGHT
8.3.4
CALCULATING THE POTENTIAL TEMPERATURE GRADIENT
ABOVE THE
MIXING HEIGHT FROM SOUNDING DATA
8.3.5
MEASURED TURBULENCE
8.3.6
DATA SUBSTITUTION FOR MISSING ON-SITE DATA
8.4
Information Passed by AERMET to AERMOD
8.5
Restrictions on the Growth of PBL Height
8.6
Initializing the Mechanical Mixing Height Smoothing Procedure
8.7
Determining The Mixing Height When the Sounding Is Too Shallow
8.8
Input Data Needs for AERMAP
8.9
Information Passed by AERMAP to AERMOD
8.10
Wind Speed & Turbulence Limits Used in Model Calculations
8.11
Using Profiles for Interpolating Between Observations
8.12
Using Measured Mixing Heights
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