[Eoas-seminar] Meteorology MS Defense for Ethan Wright, December 10, 2019, 2:00 PM, Love 353

[eoas-seminar at lists.fsu.edu]

Meteorology Seminar

Ethan Wright

Master’s Meteorology Candidate



Title:  characterizing buoy wind speed error in extreme conditions through a comparison with scatterometers and era5 Reanalysis

Major Professor:  Dr. Mark Bourassa

Date: December 10th, 2019                              Time: 2:00 PM



Location: Werner A. Baum Seminar Room (353 Love Building)
(Please join us for refreshments served outside room 353 Love @ 1:30 PM)

ABSTRACT

Buoys are a common source of remote sensing validation data over the open ocean and are one of only a small number of in situ sources in this data sparse region. Previous studies have shown the presence of a low wind speed bias for buoys in extremely high wind conditions, but the data for the high wind speed ranges are limited. Therefore, it is important to test the validity of using buoys as an in situ source for satellite calibration in high winds and high seas using a relatively long record of buoy winds. Sub-setting scatterometer and buoy wind speed differences using wave parameters provides insight into the conditions under which wind speeds diverge between these wind sources. This study uses KNMI ASCAT and NASA QuikSCAT Ocean Vector Wind datasets to compare with buoy winds processed through the Global Telecommunications System and ECMWF ERA5 Reanalysis wave data from 1999 to 2018. The scatterometer, buoy and reanalysis data are triple collocated in space by less than 25 km, and time less than 30 minutes. A probability distribution function (PDF) analysis with wind speed differences sub-divided by wind speed ranges and wave characteristics is performed to test for the dependence of wind speed differences on changing sea states. Wind speed differences are further binned by anemometer height to investigate how physical buoy characteristics affect these differences.
To account for buoy wind speed differences due to varying stability in the boundary layer, buoy winds at different anemometer heights are converted to 10 m equivalent neutral winds (U10EN) to compare with scatterometer winds. Comparisons show a difference between the high wind speed calibrations of QuikSCAT and ASCAT where QuikSCAT winds exceed buoy U10EN by nearly 4 m s-1 and ASCAT winds exceed buoy U10EN by 0.65 m s-1 on average in the 20 to 25 m s-1 buoy U10EN range. The PDFs of wind speed differences (Buoy U10EN − Scatterometer) binned by wind speed ranges vary as a function of ERA5 significant wave height and buoy anemometer height. As significant wave height increases, buoy wind speed differences associated with low anemometers decrease further than wind speed differences measured with higher anemometers. This pattern is particularly apparent when significant wave heights exceeding 4 m are combined with wind speeds exceeding 12 m s-1. Therefore, it is important to consider modification of buoy winds by the wave profile in extreme conditions prior to their application to validate remotely sensed winds.





Shel McGuire
Florida State University
Academic Program Specialist
Department of Earth, Ocean, & Atmospheric Science
1017 Academic Way, 410 Love Building (Meteorology)
Tallahassee, FL 32306
850-644-8582

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