6.2.4 Turbulence

6.2.4.1 Estimating _E from _w

Applications requiring the standard deviation of the elevation angle of the wind (e.g., see Section 6.4.4) should use the following approximation:

where

_E is the standard deviation of the elevation angle of the wind (radians)
_w is the standard deviation of the vertical component of the wind speed (m/s)
is the scalar mean wind speed (m/s). 

Weber et. al. [30] reported good performance for an evaluation using data measured at the Savannah River Laboratory for wind speeds greater than 2 m/s. In a similar study, Deihl [31] reported satisfactory performance for wind speeds greater than 2 m/s. In the Deihl study, the performance varied depending on the overall turbulence intensity. It is concluded from these studies that _E is best approximated by _w/ when wind speeds are greater than 2 m/s, and is u greater than 3 degrees.

6. METEOROLOGICAL DATA PROCESSING
  6.1 Averaging and Sampling Strategies 
  6.2 Wind Direction and Wind Speed 
      6.2.1 Scalar Computations 
      6.2.2 Vector Computations 
      6.2.3 Treatment of Calms  
      6.2.4 Turbulence 
      6.2.5 Wind Speed Profiles  
  6.3 Temperature 
      6.3.1 Use in Plume-Rise Estimates  
      6.3.2 Vertical Temperature Gradient 
  6.4 Stability 
      6.4.1 Turner's method  
      6.4.2 Solar radiation/delta-T (SRDT) method 
      6.4.3  _E method 
      6.4.4 _Amethod 
      6.4.5 Accuracy of stability category estimates 
  6.5 Mixing Height 
      6.5.1 The Holzworth Method  
  6.6 Boundary Layer Parameters  
      6.6.1 The Profile Method 
      6.6.2 The Energy Budget Method  
      6.6.3 Surface Roughness Length 
      6.6.4 Guidance for Measurements in the Surface Layer 
  6.7 Use of Airport Data 
  6.8 Treatment of Missing Data  
      6.8.1 Substitution Procedures 
  6.9 Recommendations