6.2 Wind Direction and Wind Speed

This section provides guidance for processing of in situ measurements of wind direction and wind speed using conventional in situ sensors; i.e., cup and propeller anemometers and wind vanes. Guidance for processing of upper-air wind measurements obtained with remote sensing platforms is provided in Section 9. Recommendations are provided in the following for processing of winds using both scalar computations (Section 6.2.1) and vector computations (Section 6.2.2). Unless indicated otherwise, the methods recommended in Sections 6.2.1 and 6.2.2 employ single-pass processing; these methods facilitate real-time processing of the data as it is collected. Guidance on the treatment of calms is provided in Section 6.2.3. Processing of data to obtain estimates of turbulence parameters is addressed in Section 6.2.4. Guidance on the use of a power-law for extrapolating wind speed with height is provided in Section 6.2.5. The notation for this section is defined in Table 6-2.

Table 6-1 Notation Used in Section 6.2
Observed Raw Data
ui	signed magnitude of the horizontal component of the wind vector (i.e.. the wind speed)
i	azimuth angle of the wind vector, measured clockwise from north (i.e. the wind direction)
Wi	signed magnitude of the vertical component of the wind vector
i	elevation angle of the wind vector (bivane measurements)
N	number of valid observations
Scalar wind computations
	scalar mean wind speed
	harmonic mean wind speed
	mean azimuth angle of the wind vector
	mean value of the vertical component of the wind speed
	mean elevation angle of the wind vector
	standard deviation of the horizontal component of the wind speed
	standard deviation of the azimuth angle of the wind
	standard deviation of the vertical component of the wind speed
	standard deviation of the elevation angle of the wind
Vector wind computations
	resultant mean wind speed
	resultant mean wind direction
	unit vector mean wind direction
Ve	magnitude of the east-west component of the resultant vector mean wind (positive towards east)
Vn	magnitude of the north-south component of the resultant vector mean wind (positive towards the north)
Vx	magnitude of the east-west component of the unit vector mean wind
Vy	magnitude of the north-south component of the unit vector mean wind
x, y, z	stadard right-hand-rule coordinate system with x-axis alighned towards

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