# Presentation: 376951

## Short Course on Introduction to Meteorological Instrumentation and Observation Techniques

**WIND MEASUREMENTS**
- Robert  A. Baxter, CCM
- Parsons Engineering Science
- Pasadena, CA

## Session Overview

- Goal:  Understand a general approach to measuring wind and setting up and calibrating the wind sensors

## Session Overview

- References and guidance
- Wind measurement
- Wind speed
- Wind direction

- Goal:  Understand a general approach to measuring wind and setting up and calibrating the wind sensors

## References and Guidance

| Document | Year |
| --- | --- |
| Quality Assurance Handbook for Air Pollution Measurement Systems
Volume IV:  Meteorological Measurements | 
March, 1995 |
| Meteorological Monitoring Guidance for Regulatory Modeling Applications | 
February, 2000 |

## Measurement of Wind

- Wind is a vector quantity comprised of direction and speed

## Measurement of Wind

- Wind is a vector quantity comprised of direction and speed

- _Measurement Method_
- vector quantity
- Individual scalar quantities

## Measurement of Wind

- Wind is a vector quantity comprised of direction and speed

- _Measurement Method_
- vector quantity
- Individual scalar quantities

- Most common approach is to measure the individual scalar quantities

## Wind Measurement Methods

- Mechanical
- Non-mechanical

## Wind Measurement Methods

- Mechanical
- Cup and vane
- Propeller/vane
- Non-mechanical

## Wind Measurement Methods

- Mechanical
- Cup and vane
- Propeller/vane
- Non-mechanical
- Sonic
- Hot wire

## Wind Measurement Methods

- Mechanical
- Cup and vane
- Propeller/vane
- Non-mechanical
- Sonic
- Hot wire

- Focus on mechanical methods

## Measurement Characteristics

- Siting and exposure

## Measurement Characteristics

- Siting and exposure
- Transfer function

## Measurement Characteristics

- Siting and exposure
- Transfer function
- Starting threshold

## Measurement Characteristics

- Siting and exposure
- Transfer function
- Starting threshold
- Calibration and alignment methods

## Measurement Characteristics

- Siting and exposure
- Transfer function
- Starting threshold
- Calibration and alignment methods
- Other characteristics
- Distance constant
- Damping ratio
- Delay distance

## Siting and Exposure

- _Siting_
*	**For use in air quality modeling applications, meteorological data should be representative of conditions affecting the transport and dispersion of pollutants in the “area of interest” as determined by the locations of the sources and receptors being modeled*

## Siting and Exposure

- _Siting_
*	**For use in air quality modeling applications, meteorological data should be representative of conditions affecting the transport and dispersion of pollutants in the “area of interest” as determined by the locations of the sources and receptors being modeled*

- Representativeness
- Simple Terrain
- Complex Terrain
- Coastal Locations
- Urban Locations

## Siting and ExposureSimple Terrain

## Siting and ExposureSimple Terrain

## Siting and ExposureUrban Locations

## Siting and ExposureUrban Locations

## Siting and ExposureUrban Locations

## Siting and ExposureUrban Locations

## Measurement CharacteristicsWind Speed Transfer Functions

## Measurement CharacteristicsWind Speed Transfer Functions

- Describes the relationship between the rate of rotation and the wind speed

## Measurement CharacteristicsWind Speed Transfer Functions

- Describes the relationship between the rate of rotation and the wind speed
- Determined through wind tunnel testing

## Measurement CharacteristicsWind Speed Transfer Functions

- Describes the relationship between the rate of rotation and the wind speed
- Determined through wind tunnel testing
- Linear relationship above the starting threshold of the sensor

## Measurement CharacteristicsWind Speed Transfer Functions

- Describes the relationship between the rate of rotation and the wind speed
- Determined through wind tunnel testing
- Linear relationship above the starting threshold of the sensor
- Near threshold response
- Cup anemometer
- Propeller anemometer

## Measurement CharacteristicsWind Speed Transfer Functions

- What do the transfer functions look like?

## Slide 31

## Measurement CharacteristicsStarting Threshold

*The wind speed at which an anemometer or vane first starts to perform within its specifications*

## Measurement CharacteristicsStarting Threshold

*The wind speed at which an anemometer or vane first starts to perform within its specifications*
- Applies to both wind speed and wind direction

## Measurement CharacteristicsStarting Threshold

*The wind speed at which an anemometer or vane first starts to perform within its specifications*
- Applies to both wind speed and wind direction
- Wind tunnels are the only way to measure the starting threshold

## Measurement CharacteristicsStarting Threshold

*The wind speed at which an anemometer or vane first starts to perform within its specifications*
- Applies to both wind speed and wind direction
- Wind tunnels are the only way to measure the starting threshold
- The starting threshold can be estimated by measuring the starting torque of the sensor

## Measurement CharacteristicsStarting Threshold Calculation

- T = K u2
- Where
- 		T   is the torque( g-cm2/sec2)
- 		u2   is the square of the wind speed (m/s)
- 		K   is the constant for the aerodynamic shape (g)
- u =   (T/K)

## Calibration and Operation Wind Speed

- Calibration in a wind tunnel

## Calibration and Operation Wind Speed

- Calibration in a wind tunnel
- Application of the transfer function
- Cup anemometer
- Propeller anemometer

## Calibration and Operation Wind Direction

- Vane alignment
- Sensor response and linearity

## Wind DirectionVane Alignment

- Finding true north
- Magnetic north and declination correction
- Solar methods and the “Baxter Method”
- Alignment using GPS

## Using the Step-by-Step Solar Method for Alignment

- Measure the relative pointing direction
- Measure the sun’s relative azimuth angle
- Calculate the sun’s actual azimuth angle
- Calculate the local deviation
- Calculate the cross are true alignment
- Align the wind direction sensor

## GPS Method for Alignment

- Walk off the alignment direction

## Wind DirectionVane Linearity

- Rotation through full range
- Alternative methods to protractor
- Reverse rotation

## Review of Wind Measurement

- References and guidance
- Siting and exposure
- Measurement characteristics
- Starting threshold
- Transfer function
- Calibration methods

## Slide 45

## Sun Angle

- Back