tower systemsjanuary 2001 -- ams short course on instrumentation 1 installation and use of...
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Tower Systems January 2001 -- AMS Short Course on Instrumentation
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Installation and Use of Meteorological Tower Systems
Melanie A. WetzelDesert Research Institute
and
University of Nevada, Reno
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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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
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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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
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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Examples of Existing Networks AWOS and ASOS
Oklahoma MesoNet
MesoWest
SNOTEL
Highway Networks (DOT, States)
Air Quality Networks
DOE / ARM
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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System Design Factors
Sensor characteristics Tower access Transport, construction and
maintenance Data communications options Power source System expandability
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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Process-Oriented Approach to System Design1. 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
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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 averagingmeasurements from a sensor with low resolution
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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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
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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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
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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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
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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Example of System Power Chart
Communications power drain is larger than sensor operation or data storage functions.
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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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
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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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
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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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
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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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
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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Orienting Instruments
Wind Vane
Radiative Sensors azimuth angle elevation angle
Reducing shadowing of precipitation, wind and other parameters
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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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
Tower Systems January 2001 -- AMS Short Course on Instrumentation
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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
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ReferencesDaley, 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.
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