Regional Sea Level Observations Contributions of ODINAFRICA

Transcription

1 Regional Sea Level Observations Contributions of ODINAFRICA Mika ODIDO IOC Sub Commission for Africa and the Adjacent Island States. Séminaire sur la coopération et la sensibilisation sur la gestion intégrée des zones côtières en Afrique de l Ouest (12-13 juin 2012), Dakar, Senegal

2 CONTENTS. Causes of Sea level changes How to observe sea level At the Global level At the regional level Challenges faced Examples of data available Sources of data

3 Causes of Sea Level Change. Wind waves, earthquakes, tsunamis (seconds to minutes) Tides and Storm surges (hours to days) Seasonal cycles, El Nino (years) Climate change and slow vertical earth movements (long term)

4 Sea Level Observations One of the easiest oceanographic parameters to measure. Tide pole and timer Float gauges Pressure gauges Radar Satellite Altimetry.

5 Tide Poles

6 Float Gauges

7 Radar Gauges Below: Pointe Noire, Congo Above: Inhambane, Mozambique

8 Global Sea Level Observing System - GLOSS Programme of the Joint Technical Commission for Oceanography and Meteorology (IOC/WMO). Global Core Network [GCN] of about 300 evenly distributed sea level stations for sampling global sea level variations

9 OTHER GLOSS COMPONENTS GLOSS Long Term trends [LTT] set of stations for monitoring long term trends and acceleration in global sea level (sub-set of GCN). Priority sites for GPS receiver installation to monitor vertical earth movements (contribute to long-term climate change studies) GLOSS Altimeter Calibration [ALT] stations mostly island stations, to provide an ongoing facility for mission intercalibrations GLOSS Ocean Circulation [OC] stations, includes particular gauge pairs at straits and in polar areas (complements altimeter coverage of open sea.

10 GLOSS Data Streams Mean Sea Level Data to Permanent Service for Mean Sea Level (UK). Delayed mode higher frequency data University of Hawaii Sea Level Centre (UHSLC) and PSMLS Fast higher frequency data UHSLC GPS data to TIGA data centre of the International GPS Service. THERE ARE EXISTNG STATIONS WHICH DO NOT PROVIDE DATA!!

11 Review of Sea Level proposals for Africa (September 2003). (i) GLOSS Core Network (GCN) proposed a network of 32 continental and island stations for Africa. (ii) ROOFS-AFRICA recommended 27 additional sites for sealevel & other measurements as the basis for a comprehensive observing system for Africa ODINAFRICA-III reviewed these proposals and selected 19 priority stations.

12 Criteria set for selection. High spatial resolution [improve quality of data needed for scientific and management purposes]. Sufficient time series [update the tidal constituents, and improve predictions needed to for navigation etc] Monitoring sea level so as to understand and forecast: a) processes such as the variation of coastal currents, b) upwelling along the coasts of Cote d Ivoire, Ghana and Namibia, c) Storm surges and associated flooding caused by tropical cyclones.

13 IMPLEMENTATION PLAN upgrade and expand African network for in-situ measurements and monitoring of ocean variables, particularly sea-level provide near real-time observations of sea levels building adequate capacity for collection, analysis and management of sea-level data Indian Ocean Tsunami 26 December 2004, one of the worst marine disasters recorded impacted greatly on the implementation plan developed

14 GLOSS Stations African coast & nearby islands.

15 Red Sea GLOSS stations. -Suez -Djibouti: An OTT tide gauge from 1995, replaced by a radar gauge in 2007 Additional Stations: -8 stations installed by Suez Canal Authority -Maybe another by Red Sea Port Authority at Hurgada city?? -Port Sudan, Sudan [ (maintained by Survey Dept) -Port Sudan, installed 1998 for IMR by PERGSA never functioned -Maybe Asmara??

16 Red Sea LEFT: Kaelesto radar gauge in Djibouti Port Sudan SML-2B tide gauge Old tide gauge in Suez Canal (replaced by WTR9/Aanderra??)

17 NW Indian Ocean GLOSS Stations operational. -Kenya: Lamu from 1996 & Mombasa from 1986 (gaps) -Tanzania: Zanzibar from 1986 & Mtwara -Seychelles: Port Victoria Additional Stations: -Kenya: Kilifi, Shimoni and extra Lamu -Tanzania: Dar es Salaam & historical station in Tanga -Seychelles: historical data from Port Victoria (Hodoul) & Praslin -Somalia: short time series Mogadishu and Kismayo

18 Kenya Kilifi tide gauge Mombasa tide gauge Lamu 2 gauge Lamu tide gauge

19 Seychelles and Tanzania Above: Dar es Salaam Below: Zanzibar Pointe Larue, Mahe

20 SW Indian Ocean Mozambique: Pemba & Inhambane - South Africa: Durban, Port Elizabeth, Simons Town, Marion Is. - Mauritius: Port Louis: 1986, upgraded 2008, and Rodrigues - France: Dzaoudzi, and Pointe Des Galets Additional Stations: -Madagascar: Tamatave, (historical data for NosyBe, Tulear & Fort Dauphin)

21 Mozambique Stations Kalesto gauges at Inhambane & Pemba

22 Mauritius Stations Port Louis & Rodrigues

23 South Africa and Namibia

24 Richards Bay 1998 Float gauge in Esat London 1996????

25 SE Atlantic GLOSS stations. - Simonstown - Walvis Bay - Lobito

26 CE Atlantic GLOSS stations. - Sao Tome - Nigeria: Lagos - Cote d IvoireAbidjan - Ghana: Takoradi - Aberdeen Point - Guinea: Conakry - Congo: Pointe Noire Additional Stations: -Benin: Cotonou -Togo: Lome -Cote d Ivoire: San Pedro -Ghana historical from Tema

27 NE Atlantic Below: Morocco tide gauge network Dakar, Senegal Nouakchott, Mauritania

28 RED Real time, BLUE delayed mode, GREEN proposed.

29 Old tide gauge at Alexandria harbour

30 GLOSS Stations Current Status Apr 2012

31 In collaboration with the Instituto Geofísico D. Luís (IDL), Lisbon, Portugal Selected stations in Takoradi (Ghana), and Inhambane and Pemba (Mozambique) GNSS (Global Navigations Satellite Systems: GPS, GLONASS and GALILEO) receivers Benefits: Collocation of GPS stations. provide the connection between the horizontal and the vertical datum Monitoring of crustal motions at the location Derivation of absolute or climate related signals in mean sea level from the tide records Indication of whether tide gauge is sinking into the harbour or it is the sea rising

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33 Challenges to be Addressed Installation of stations Maintenance of existing stations (incl. leveling of benchmarks...) Access to, and utilization of data from the stations Relocation of stations - siltration/erosion - construction in ports/harbours - extreme events (e.g storms...) (continuity of data when equipment or location changed

34 Siltration at Pointe Noire jetty Nosy Be the jetty after storm

35 RELEVANT WMO PLANS Plans to install 6 hydro-meteorological stations (including tide stations) in Mauritania, Cape Verde, Senegal and Gambia. Nouadhibou North West Mindelo 16 53' North 25 00' West Praia 14 54' North 23 30' West Saint Louis North West Joal North West Banjul 13 27' North 16 34' West

36 Monthly and Annual means from Takoradi

37 Monthly and Annual means from Dakar

38 2004 Tsunami signals Arrival time of signals from the Indian Ocean Tsunami at tide gauges along the African coast: left- Port Louis - Mauritius, Pte La Rue - Seychelles, Lamu Kenya. Tsunami arrival time at Takoradi

39 Useful Websites UHSLC ( PSMSL (