Title: Installation and Use of Meteorological Tower Systems
1Installation and Use of Meteorological Tower
Systems
- Melanie A. Wetzel
- Desert Research Institute
- and
- University of Nevada, Reno
2Objectives
- 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
3Why 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
4Examples of Existing Networks
- AWOS and ASOS
- Oklahoma MesoNet
- MesoWest
- SNOTEL
- Highway Networks (DOT, States)
- Air Quality Networks
- DOE / ARM
5System 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
8Criteria 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
10 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
11 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
15Considerations for Tower Setup
- Sensor placement
- Sensor orientation
- Shadowing
- Wind blockage
- Spatial representativeness
16Tower Types
- Poles with guy lines
-
- Tripod
- Triangular
- Sectioned
- Pivoting
- Use of structures
17 Orienting Instruments
- Wind Vane
- Radiative Sensors
- azimuth angle
- elevation angle
- Reducing shadowing of precipitation, wind and
other parameters
18 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
19Quality 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
20References
- 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.