THE ROLE OF TELECONNECTION PATTERNS IN WAVE CLIMATE AND STORMS DISTRIBUTION: THE SW SPANISH

AND WALES COASTS EXAMPLES.

Nelson Rangel-Buitrago ,Giorgio Anfuso, Mike Phillips, Tony Thomas

This work is a contribution to the RESISTE Research Project (CGL2008-00458/BTE, supported by the Spanish Ministry of Science and Technology and by European

Funds for Regional Development – F.E.D.E.R.), the Research Project GERICO (CGL 2011–25438) and to the Andalusia P.A.I. Research Group no. RNM-328.

HAZARDS - VULNERABILITY - RISK

Over the past decades several great storms and hurricanes have caused important economic losses and scores of deaths along the coastline of the world.

Source:EEA

STORMS IN EU

Recorded events Number of fatalilies Number of people afected Overal lossses Insured losses

Nº 155 729 3803 44.338 (billion) 20.532 (billion)

Rank 2 4 2 2 1

Overal losses associated with disasters caused by natural hazards in europe (1998 – 2009)

OUR GOAL This work presents the characterization of wave climate and energy, coastal storms and their recurrence intervals, related to several regional cycles in Cadiz (SW Spanish Atlantic coast), Tenby and Swansea (S Wales, UK) - utilizing 22 years of wave data captured between 1987 and 2008.

METHODS

Wave data

SPAIN (CADIZ) Scalar buoy nº 1316 (36.50ºN; 6.33ºW), a waverider-datawell instrument which is located at a water deep of 21 m, in front of Cadiz city.

WALES (TENBY) Data captured at a point located 9 kilometers to the southeast (51.6ºN; 4.58ºW) within Carmarthen Bay derived from hind-casts produced by the MetOffice. This point is located in a depth of 28 m.

Tenby - BBC

Cadiz

Tenby - BBC

Cadiz –vayaciudad.com

METHODS

The Dolan & Davis (1992)

Storm Power Index

Hs2 td

Hs = significant wave height

td = storm duration in hours

STORM CHARACTERIZATION

Threshold= 2.5 m CADIZ 3.5 m TENBY

Minimum storm duration = 12 hr Inter-storm period = 24 hr

Rangel & Anfuso (2011)

CLASS RANGEWEAK < 515

MODERATE 515 - 1225

SIGNIFICANT 1225 - 2537

SEVERE 2538 - 5167

EXTREME > 5167

TELECONNECTION PATTERNS

The term Regional Cycle and Teleconnection Pattern are terms referred to a recurring and persistent, large scale pattern of pressure and circulation anomalies that span vast geographical areas (Hatzaki et al., 2006).

• North Atlantic Oscillation – NAO .

• East Atlantic Pattern – EA .

• East Atlantic/Western Russia – EA/WR .

• Scandinavia – SCAND.

• Polar/Eurasia – POL.

• East – North Pacific Pattern – EP–NP.

• Pacific/North American Pattern – PNA .

• Arctic Oscillation – AO.

Wave Climate

Wave Height (Hs) results showed a clear seasonal behavior and cyclic pattern.

Wave Climate

Wave Climate During the winter season, waves rapidly increased in height, reaching peak

values (Hs = 1.2 m, Cadiz, Hs = 2.1 m, Tenby) between December and January.

When consideration was given to the entire investigated period, there was a significant variation in average monthly wave height.

When extreme wave conditions were considered, the highest monthly value was December 1989, with an average value of extreme wave height of 4.6 m in Tenby and 2.5 m in Cadiz.

Quasi-periodic 2 to 4 year cyclical behavior in significantly high wave. Similarly, spectral analysis of time series of extreme waves, based on the Fourier transformation (Boashash,

2003), indicated a cyclic trend of 3 years.

FACTS

Wave Climate

Wave Energy

Results show that the monthly average wave energy flux was 14.7 kW/m in Tenby and 4.7 kW/m in Cadiz, and respectively reached values of 155.5 kW/m and 36.6 kW/m during the winter season.

STORM POWER

Linear regression analyses and Pearson

correlation tests were performed considering the

annual and monthly wave data (Hs and Hs99),

storminess indices and teleconnection patterns.

The analysis of annual and monthly datasets gave

very different result, the latter presenting

clearer trends .

Multiple linear regression analysis between wave

data, storminess indices and the teleconnection

patterns indicated that approximately 40% of the

change in monthly wave data and all used

storminess indices related to changes in the eight

teleconnection patterns used in this work.

Drivers of change being the AO, with 21.45%, and

NAO, with the 19.65%. Both being important

controllers on short- and long-term climatic

variability in North Atlantic Ocean, Europe and the

Mediterranean Basin.

The role of NAO - AO

It is interesting to remark that high energy values were observed when neutral to strong negative NAO and AO phases occurred and also when there were abrupt changes, e.g. from positive to negative phases without passing through a neutral phase.

The role of NAO - AO 1980s General predominance of positive NAO phases, AO trend changed in 1988. Considering storminess, the 1980s can be classified as a period of ‘calm’ due to the low recorded condition in wave heights and storminess. Tenby showed many storms in 1988.

1980s 1990s 2000s

The role of NAO - AO

The role of NAO - AO

1990s NAO and AO indices presented the predominance of positive phases, and it was generally recorded low storm activity, the 1995 being the only year that recorded strong negative phases –many storms in Cadiz.

1980s 1990s 2000s

The role of NAO - AO

The role of NAO - AO 2000–2012 Characterized by cyclic behavior of both NAO and AO indices and wave climate and storminess. Important storm conditions observed in Tenby in 2006 (and in Cadiz in 2009).

1980s 1990s 2000s

The role of NAO - AO

The role of NAO - AO

Climatic anomalies were associated with an extreme persistence of negative phases of AO and NAO indices and an exceptional Northern Hemisphere mean atmospheric circulation episode reflected by the distribution of the geo-potential height anomalies at 500 mb.

Thanks! For further Information nelsonrangel@mail.uniatlantico.edu.co