REFERENCE WIND SPEED AND HEIGHT

The reference height for winds (z_ref ), and thus the reference wind speed (u_ref ), is selected as the lowest level of data which is available between 7z_o & 100m. Although the current version of AERMOD can not accept a separate z_ref for offsite data, we believe that a separate z_ref should be selected for each data set being used.

If no valid observation of the reference wind speed or direction exists between these limits the hour is considered missing and a message is written to the AERMET message file. For the wind speed to be valid its value must be greater than or equal to the threshold wind speed. AERMOD processes hours of invalid wind  speed, e.g. calms, in the same manner as ISC (EPA calms policy).

All observed wind speeds in a measured profile that are less than u_TH are set to missing and are therefore not used in the construction of the wind speed profile (profiling of winds is accomplished in AERMOD).

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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