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Showing posts with label Indian Ocean. Show all posts
Showing posts with label Indian Ocean. Show all posts

Saturday, October 23, 2021

AFRICA - 10 poorest countries in Africa; how do they live and what needs to be done?

Title:
10 poorest countries in Africa; how do they live and what needs to be done?
 
Author:
Emmanuel Abara Benson
 
Published:
Business Insider Africa, 16 October 2021
 
From the article:
* Most of the world's poorest people are concentrated in Africa. These people live in abject poverty, many of them on less than a dollar per day. 
 
* The ten poorest African countries are scattered across West Africa, Southern Africa, the Horn of Africa and the Indian Ocean. 
 
* There are two common characteristics similar to them all – man-made and natural disasters.
 

Tuesday, October 20, 2020

Geophysical Journal International (2020) - Assessing swells in La Réunion Island from terrestrial seismic observations, oceanographic records and offshore wave models

Title:
Assessing swells in La Réunion Island from terrestrial seismic observations, oceanographic records and offshore wave models
 
Authors:
E J Rindraharisaona, E Cordier, G Barruol, F R Fontaine & M Singh
 
Published:
Geophysical Journal International, Volume 221, Issue 3, June 2020, Pages 1883-1895
 
Summary:
La Réunion Island in the southwest Indian Ocean is seasonally affected by austral swells among which some extreme events may have strong impacts on coastal infrastructures. The very limited number of sensors available on and around the island and in the whole SW Indian Ocean impedes any direct monitoring of the swell activity. In this study, we analyse direct observations of the ocean swell by combining terrestrial measurements of the microseismic noise with in situ oceanographic observations issued from two pressure gauges and an Acoustic Doppler Current Profiler (ADCP), together with swell numerical modelling. The reliability of the terrestrial seismic station to characterize the ocean activity in both the primary and secondary microseisms peaks (PM and SM, respectively), and also in the long period secondary microseismic peak (LPSM) for the case of La Réunion Island is presented and discussed here. By computing the hourly RMS of the PM and LP(SM) amplitudes, we establish a transfer function between the PM and (LP)SM amplitude and the maximum wave height, which appears to be valid for any PM and LPSM amplitudes >0.15 μm and >1.0 μm, respectively. The correlation coefficient between the PM amplitude and the wave height is >0.92. It suggests that the PM amplitude can be used as a robust proxy for the swell height and may help calibrating the wave heights from other independent observable. For some swell events, we observe LPSM that correlate well (>0.91) with the local wave height suggesting a generation by coastal swell reflection. From polarization and spectral analyses, directions and periods of swells are also well retrieved from seismic data. Finally, continuous measure of the SM amplitude shows that it can be used as precursor information for distant swells that may hit La Réunion Island a few days after their generation in the southern Indian Ocean.