Determining The Mixing Height When the Sounding Is Too Shallow

The left hand side of eq. (9) 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 z_ic. This is accomplished as follows:

• Determine d/dz in the top 500m layer of the sounding. However, if part of the 500m layer is within the first 100m’s of the PBL the layer should be reduced (to a minimum thickness of 250m) to avoid using the portion of the sounding that is below 100m. If the above conditions can not be satisfied then z_ic is defined as missing.

• Extend the sounding by persisting d/dz up and recomputing z_ic.

• Provide warning messages which tell users

• The height of the actual sounding top,

• That d/dz has been extrapolated above the sounding z_ic, and

• That z_ic has been recomputed. 

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

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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