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Energies 2018, 11(1), 137; https://doi.org/10.3390/en11010137

Variance Characteristics of Tropical Radiosonde Winds Using a Vector-Tensor Method

1
Interdisciplinary Graduate School, Nanyang Technological University, Singapore 639798, Singapore
2
Energy Research Institute @ NTU, Nanyang Technological University, Singapore 637141, Singapore
3
UC, Singapore University of Social Sciences, Singapore 599491, Singapore
4
School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore
*
Authors to whom correspondence should be addressed.
Received: 7 November 2017 / Revised: 20 December 2017 / Accepted: 22 December 2017 / Published: 5 January 2018
(This article belongs to the Section Energy Sources)
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Abstract

In this paper, an exploratory study on the variance characteristics of upper-air winds in a near-equator monsoon region is presented. The data were obtained from historical radiosonde observations from up to 250 stations within the region of interest for the period between 1954 and 2013. An alternative method based on vector statistics was employed in this study which characterises the mean by a vector and the variance by a tensor. Unlike the conventional approach of using scalar wind speeds, this vector-tensor approach allows the directional properties of the variance to be studied. A suite of statistics to describe the geometric properties of the variance tensor was also developed. These characterise the size of the variance, its degree of anisotropy, and the alignment of the preferred direction (if anisotropy is present) with the direction of the mean wind vector. Through analysis of these statistics, several salient trends were observed for the middle troposphere. It was found that the variance size and anisotropy exhibit significant variation with height whereas the alignment with the mean vector varies with the mean wind magnitude instead. It was also found that the scalar variance increases with mean wind speed. View Full-Text
Keywords: wind characteristics; variance; covariance matrix; random vector; radiosonde; monsoon; tropical; high-altitude wind characteristics; variance; covariance matrix; random vector; radiosonde; monsoon; tropical; high-altitude
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Tieo, J.-J.; Koh, T.-Y.; Skote, M.; Srikanth, N. Variance Characteristics of Tropical Radiosonde Winds Using a Vector-Tensor Method. Energies 2018, 11, 137.

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