Installation and Use of Meteorological Tower Systems

1
Installation and Use of Meteorological Tower
Systems

• Melanie A. Wetzel
• Desert Research Institute
• and
• University of Nevada, Reno

2
Objectives

• Approach the use of instrumented tower systems as
  a process
• Present technical options for sensor and tower
  characteristics
• Describe factors and decisions critical to
  installation
• Provide examples of tower system applications

3
Why Use Towers ?

• Standardization (generally to 10 m height) with
  respect to vertical profiles of wind, temperature
  and other boundary layer parameters
• Ability to apply parameterizations for other
  heights such as the logarithmic wind speed (S)
  vs. height (H) equation, Sa Sb
  (Ha/Hb)p Exponent p is typically in the
  range 0.14 for smooth terrain to 0.25 for
  rough terrain
• Reduction in blockage and shadowing from
  obstructions
• Increased availability of solar power improved
  communications

4
Examples of Existing Networks

• AWOS and ASOS
• Oklahoma MesoNet
• MesoWest
• SNOTEL
• Highway Networks (DOT, States)
• Air Quality Networks
• DOE / ARM

5
System Design Factors

• Sensor characteristics
• Tower access
• Transport, construction and maintenance
• Data communications options
• Power source
• System expandability

6
Process-Oriented Approach to System Design

• 1. Select sensors
• 2. Specify data acquisition
• 3. Design power system
• 4. Program the datalogger
• 5. Install equipment
• 6. Plan heights for equipment
  installation
• 7. Design tower setup and installation
  procedures
• 8. Orient instruments
• 9. Install and initialize software
• 10. Maintain data collection and data
  quality

7
Steps for Specifying Instrumentation

• Determine scope of project and potential
  applications
• Identify needs for simultaneous auxiliary data
• Select types of instrumentation (parameters,
  resolution, range)
• Determine sampling rates and length of study
• Acquire specific instruments (cost, availability,
  etc)
• Conduct analysis of extreme conditions (heat,
  cold, icing, wind)

Example of time averaging measurements from a
sensor with low resolution
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Criteria for Sensor Selection

• Sensor range, resolution, precision
• Ruggedness and suitability for local
  environmental conditions
• Cost of acquisition, operation and maintenance
• Availability (lead time, access to replacement
  parts)
• Manufacturer history
• Software ease of use and compatibility
• Technical support
• Calibration requirements
• Time response and sampling frequency
• Compatibility with other sensors

9
Data Acquisition Guidelines

• Determine data channel types and number
• Calculate memory requirements
• Select data storage, access, editing and merging
  methods
• Define protocol for missing data
• Determine procedures for identifying drift or
  calibration errors

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Options for System Power

• Calculate power needed
• Instruments
• Datalogger
• Communications
• Heaters
• Evaluate power sources
• Direct power
  
  (capacity, reliability)
• Fueled generators
• Wind and solar energy
• Battery reserve (temperature
  
  
  effects and
  minimum capacity )
• Provide adequate monitoring of power supply and
  interruptions

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Example of System Power Chart
Communications power drain is larger than sensor
operation or data storage functions.
12
Programming for Data Acquisition

• Set up the datalogger program prior to field
  deployment
  
• Develop data capture protocol
  (dial-in, site visit, etc)
• Design data archival and documentation procedures

13
Installation of Equipment at Site

• Assess possible hazards -- lightning, vandalism,
  animals, accidents
• Select location most appropriate to project
  objectives and longevity
• Avoid locales which are unrepresentative (fog,
  valley inversions)
• Identify and map potential obstructions or
  conditions
• dust
• wind
• temperature
• solar illumination
• precipitation

14
Proper Heights for Equipment Installation

• Wind velocity standard height vs. wind turbine
  height
• Solar panel location for site power vs solar
  energy survey
• Need for multiple or non- standard heights
• Access to control panel and communications

15
Considerations for Tower Setup

• Sensor placement
• Sensor orientation
• Shadowing
• Wind blockage
• Spatial representativeness

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Tower Types

• Poles with guy lines
•  
• Tripod
• Triangular
• Sectioned
• Pivoting
• Use of structures

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Orienting Instruments

• Wind Vane
• Radiative Sensors
• azimuth angle
• elevation angle
• Reducing shadowing of precipitation, wind and
  other parameters

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On-site Software Installation

• Test communications to and from tower
• Download program to site datalogger
• Select and set time/date
• Record local site parameters
• latitude/longitude
• elevation
• location on map

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Quality Control and Data Management

• Prescribe schedule to routinely check data
  quality
• Monitor power supply
• Assess need to relocate sensors
• Evaluate benefits of sensor upgrade
• Prepare documentation for operations and
  training
• Standard Operating Procedures
• Site photos and diagrams
• Log sheets for maintenance
• Data format and archival schedule
• Sensor calibration history 

20
References

• Daley, R., 1991 Atmospheric Data Analysis.
  Cambridge University Press, 457 pp.
• DeFelice, T.P., 1998 An Introduction to
  Meteorological Instrumentation and Measurement,
  Prentice Hall, New Jersey, 229 pp.
• Webster, J.G., ed., 1999 The Measurement,
  Instrumentation and Sensors Handbook. CRC Press,
  916 pp.