You are here

Adjustment of Visually Observed Ship Winds (Beaufort Winds) in ICOADS

Title: Adjustment of Visually Observed Ship Winds (Beaufort Winds) in ICOADS.
40 views
6 downloads
Name(s): Li, Keqiao, author
Bourassa, Mark Allan, professor directing thesis
Smith, Shawn R. (Shawn Richard), committee member
Liu, Guosheng, committee member
Chagnon, Jeffrey M., committee member
Florida State University, degree granting institution
College of Arts and Sciences, degree granting college
Department of Earth, Ocean, and Atmospheric Science, degree granting department
Type of Resource: text
Genre: text
Issuance: monographic
Date Issued: 2016
Publisher: Florida State University
Place of Publication: Tallahassee, Florida
Physical Form: computer
Physical Form: online resource
Extent: 1 online resource (43 pages)
Language(s): English
Abstract/Description: ABSTRACT The bias adjustment of visually estimated ship winds in the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) is addressed through the comparison to the QuickSCAT scatterometer equivalent neutral winds. We assume that visually estimated winds and satellite scatterometer winds share similar characteristics, which are a function of stress rather than wind speed, and treat the estimated ship winds as equivalent neutral winds. Under such an assumption, we use statistical analyses to calculate the bias correction for estimated ship winds. Because observation practices vary by country and data provider, ICOADS identifies datasets by "deck" which is a number that allows for differentiating the source of the records (different deck numbers indicate different data collections provided to ICOADS, each which may contain one or more sources/countries). Three ICOADS decks 792, 926, and 992 contain the vast majority (~90%) of collocated visually estimated ship winds covering the time period November 1999-October 2009. The Root-Mean-Square difference between these visually estimated ship winds and scatterometer winds are 3.0ms-1, 2.8ms-1 and 2.9ms-1 for each major deck respectively. Following the methodology of Freilich (1997) and Freilich and Dunbar (1999), we numerically show that for lower wind speeds (0ms-1-5ms-1 in this case) that the random error in the component of the visually estimated ship winds causes an artificial appearance of an overestimation relative to satellite scatterometer winds. We also extend this statistical artifact test to test higher wind speeds (12ms-1-18ms-1 in this case) through a Monte Carlo approach. An apparent slight drop of the conditional sample means relative to reference line is shown to be a statistical artifact. These artificial biases are properly accounted in this study. A new bias correction, LMS correction, is calculated and also compared to prior corrections such as Lindau (1995). This new bias correction is available for wind speeds ranging from 0ms-1 to 17ms-1, because there are too few spatial and temporal collocated matches at wind speed greater than 17ms-1. We are limited in our ability to perform the adjustments required for intercallibration because when comparing visual winds to scatterometer winds the necessary wind speed observations are rare and small in magnitude.
Identifier: FSU_2016SP_Li_fsu_0071N_13246 (IID)
Submitted Note: A Thesis submitted to the Department of Earth Oceanic and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science.
Degree Awarded: Spring Semester 2016.
Date of Defense: March 29, 2016.
Keywords: Beaufort winds, bias adjustment, ICOADS, Lindau's (1995) correction, LMS correction
Bibliography Note: Includes bibliographical references.
Advisory Committee: Mark A. Bourassa, Professor Directing Thesis; Shawn R. Smith, Committee Member; Guosheng Liu, Committee Member; Jeffrey Chagnon, Committee Member.
Subject(s): Meteorology
Persistent Link to This Record: http://purl.flvc.org/fsu/fd/FSU_2016SP_Li_fsu_0071N_13246
Owner Institution: FSU

Choose the citation style.
Li, K. (2016). Adjustment of Visually Observed Ship Winds (Beaufort Winds) in ICOADS. Retrieved from http://purl.flvc.org/fsu/fd/FSU_2016SP_Li_fsu_0071N_13246