Reference Basic Wind Speed for Selected Towns/Cities in Ethiopia
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Date
2016-07
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Addis Ababa University
Abstract
A data on three hourly wind speeds, from 18 meteorological centre of Ethiopia Meteorological
Department, have been collected. The daily gust wind data have been processed for annual
maximum wind speed in m/sec for each site. This research paper presents an attempt made
towards preparing a wind zone map based on observed wind speeds at each weather station in the
country. The data used were annual maximum 180 minute average wind speeds recorded at about
10 m above ground level. These 180 minute average wind speeds were changed to 10 minute
mean wind speeds by the factor 1.32. Several probability distributions were tested for suitability
and Extreme Value Type I (log Gumbel) distribution was found to be the best fitting distribution
for the maximum wind speeds at Arba Minch and Hawassa. Log Pearson distribution was found
to be the best fitting distribution for the maximum wind speeds at Dire Dawa and Kombolcha.
Log Normal distribution was found to be the best fitting distribution for the maximum wind
speeds at Addis Ababa, Bahir Dar, Debre Markos, Debre Zeit, Gode, Gondar, Gore, Jimma,
Kibre Mengist, Mekelle, Metehara, Negelle, Nekemte and Robe. An attempt to demarcate wind
speeds for the selected stations was prepared using the 5, 10, 15, 20, 25, 30, 50, 100, 200, 500
and 1000 year return period wind speeds resulted from the best fitting probability distributions.
This map was based on basic wind speeds calculated from actual annual maximum records of
each station. The basic wind speed values ranged from 30m/sec to 45m/sec.
Keyword: Wind speed, Fitting distribution method, Return period
Description
Keywords
Wind speed, Fitting distribution method, Return period