TOWARD OBJECTIVE, STANDARDIZED INTENSITY ESTIMATES FROM SURFACE WIND SPEED OBSERVATIONS
Bulletin of the American Meteorological Society
Volume 91, Issue 12. Pgs 1665–1681.
Link to PDF >> http://journals.ametsoc.org/doi/pdf/10.1175/2010BAMS2942.1
Extreme wind climatology and event-specific intensity assessments rely heavily on surface wind field observations. The most widely used platforms sited at airports are the Automated Surface Observing System (ASOS) and its predecessor, the Automated Weather Observing System (AWOS). The terrain immediately surrounding most of these stations may be nominally characterized as aerodynamically very smooth due to the runways and flat expanses of grass that define most airport layouts. Outside of most airports, a wide spectrum of marine, open, suburban and heavily built-up terrain conditions are present. The results of this research indicate that the wind speeds recorded by AWOS/ASOS are deeply sensitive to this terrain. Powell et al. (1996) has shown that direct usage of the raw surface data can introduce surface-layer wind speed errors on the order of 30-40% due to terrain effects. Similar values are observed for gust speeds in this paper, when averaging technique and anemometer response characteristics are considered. A solution is developed to automatically compute the directional effective roughness length (z0) values using simple averages of peak-to-mean wind speed ratios (gust factors). Adjustments are also made to cup anemometer data to correct for gust attenuation caused by frequency response and block averaging. A new effective surface roughness database is offered, which can be used to convert a raw wind speed measurement (sustained or gust) to any predefined aerodynamic metadata (height, terrain, and average period) to serve the needs of operational and research users.
Thanks for visiting this site. If you made it this far, you must have an interest in wind field standardization. Probably the most important piece of information to get across to you first is that this is not a funded project. The work is largely the result of an ad-hoc collaboration between UF and ARA, with some support provided by the University Scholars Program for an undergraduate research assistant. This was a labor of love, and I spent many late nights working on it so as not to interrupt my funded research activities.
Second, while I am confident in the methodology, I am sure there are many improvements to be made. I hope I did a good job of laying out the limitations in the paper. Feedback is always welcome.
Third, I am big believer in collaboration and openness. Working in isolation is not good for the research product. I am happy to share my code and data, assuming there is good intent.
Fourth, I really appreciate the help I received from my colleagues. Anton Beljaars and Craig Miller were especially helpful. Mark Powell has been a long-time supporter, and his research has inspired many of my efforts, including this one. Several other researchers whom I do not know personally were a great inspiration, particularly C.S.B. Grimmond who has written several excellent papers on surface roughness. All that being said, the opinions and findings in the paper are mine and mine alone. They do not necessarily reflect the opinions of anybody that provided assistance on this project.
Lastly, I will be updating this website as time permits.
January 21, 2011
Please email Forrest Masters to with any questions or requests for data.