Tower SystemsJanuary AMS Short Course on Instrumentation 1 Installation and Use of Meteorological Tower Systems Melanie A. Wetzel Desert Research Institute and University of Nevada, Reno

Tower SystemsJanuary AMS Short Course on Instrumentation 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

Tower SystemsJanuary AMS Short Course on Instrumentation 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, S a = S b (H a /H b ) 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 SystemsJanuary AMS Short Course on Instrumentation 4 Examples of Existing Networks  AWOS and ASOS  Oklahoma MesoNet  MesoWest  SNOTEL  Highway Networks (DOT, States)  Air Quality Networks  DOE / ARM

Tower SystemsJanuary AMS Short Course on Instrumentation 5 System Design Factors  Sensor characteristics  Tower access  Transport, construction and maintenance  Data communications options  Power source  System expandability

Tower SystemsJanuary AMS Short Course on Instrumentation 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

Tower SystemsJanuary AMS Short Course on Instrumentation 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

Tower SystemsJanuary AMS Short Course on Instrumentation 8 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 SystemsJanuary AMS Short Course on Instrumentation 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

Tower SystemsJanuary AMS Short Course on Instrumentation 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

Tower SystemsJanuary AMS Short Course on Instrumentation 11 Example of System Power Chart Communications power drain is larger than sensor operation or data storage functions.

Tower SystemsJanuary AMS Short Course on Instrumentation 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

Tower SystemsJanuary AMS Short Course on Instrumentation 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

Tower SystemsJanuary AMS Short Course on Instrumentation 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

Tower SystemsJanuary AMS Short Course on Instrumentation 15 Considerations for Tower Setup  Sensor placement  Sensor orientation  Shadowing  Wind blockage  Spatial representativeness

Tower SystemsJanuary AMS Short Course on Instrumentation 16 Tower Types  Poles with guy lines  Tripod  Triangular  Sectioned  Pivoting  Use of structures

Tower SystemsJanuary AMS Short Course on Instrumentation 17 Orienting Instruments  Wind Vane  Radiative Sensors  azimuth angle  elevation angle  Reducing shadowing of precipitation, wind and other parameters

Tower SystemsJanuary AMS Short Course on Instrumentation 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

Tower SystemsJanuary AMS Short Course on Instrumentation 19 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

Tower SystemsJanuary AMS Short Course on Instrumentation 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.