regional climate variability and change · regional climate variability and change. 1 . ... source:...

Regional Climate Variability and Change

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Dr. Cedric J. VAN MEERBEECK – Climatologist ([email protected])

Ms. Wazita B. SCOTT – Assistant Climate Forecaster ([email protected])

http://rcc.cimh.edu.bb

mailto:[email protected]

mailto:[email protected]

http://rcc.cimh.edu.bb/



Climate variability and predictability in the Caribbean

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Adapted from: GFCS

Weather, Climate Variability and Climate Change

[email protected]

variability

change

variability

Modes of Tropical Variability

5/23/13 Laing, 2013 CARICOF Training Workshop 4

Decadal Oscillations

Main modes of variability influencing our climate at seasonal to inter-annual time scales

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ENSO NAO Saharan dust MJO

Our Caribbean Climate Outlook Newsletter tells us: EL NIÑO • El Niño is…

– Warmer than normal sea surface temperatures across the east-central equatorial Pacific (off the coast of South America).

– Due to ocean currents and winds shift near equator.

– Occurs every 2-7 years • El Niño stabilises the atmosphere, tears up

storm clouds and leads to dryness in our region… EXCEPT northern Caribbean, where El Niños tend to bring more dry season rains.

• El Niño 2015, the 2nd strongest since at least 1950, will last throughout the 2015-6 dry season.

Source: CariCOF Caribbean Climate Outlook Newsletter

El Niño conditions

Normal conditions

WETWET

WET

DRY

DRYDRY

El Niño events involve unusual warming of the eastern equatorial PacificOcean. They typically occur every 2-7 years and last about 6-18 months.During the dry season, El Niño often weakens the development of rain-and thunderstorms in the eastern and southern Caribbean.

Why the ongoing drought?

Drought & El Niño in time Most of the intense droughts coincide with El Niño

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St Lucia, G Charles SPI

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La Niña

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Essentially the opposite of El Niño

Unusually cold ocean temperatures in the tropical Pacific

The impact on rainfall also mirrors El Niños

Currently in the news – drought!!

Antigua From August: “No surface water exploitable, 83% desalination” (Antigua & Barbuda Met Services) From October: 100% desalinated water

Barbados record driest year resulting in water outages in central and northern part of the island.

St. Kitts & Nevis water rationing resumes in January 2016 after second driest year on record. No water sold to cruise ships since September.

St. Lucia two driest years on record in 2014 & 2015 led to water restrictions for all households.

Dominica Tropical Storm Erika amidst drought: 1.3 billion EC$ damage and losses.

Potworks Dam in Antigua

Mona reservoir in Jamaica

Carraizo reservoir in Puerto Rico

https://anumetservice.wordpress.com/2015/08/17/antigua-is-out-of-surface-water-again/ http://jamaica-gleaner.com/article/lead-stories/20150807/drought-affecting-lives-across-caribbean http://www.washingtontimes.com/news/2015/aug/5/parched-caribbean-faces-widespread-drought-water-s/?page=all http://jamaica-gleaner.com/article/lead-stories/20150706/st-thomas-struggles-cope-water-crisis http://www.jamaicaobserver.com/news/Drought-fuels-bush-fires-in-Manchester

2015: record dry in many places


Antigua From August: “No surface water exploitable, 83% desalination” (Antigua & Barbuda Met Services) From October: 100% desalinated water

Barbados record driest year resulting in water outages in central and northern part of the island.

St. Kitts & Nevis water rationing resumes in January 2016 after second driest year on record. No water sold to cruise ships since September.

St. Lucia two driest years on record in 2014 & 2015 led to water restrictions for all households.

Dominica Tropical Storm Erika amidst drought: 1.3 billion EC$ damage and losses.

Dominica after TS Erika https://anumetservice.wordpress.com/2015/08/17/antigua-is-out-of-surface-water-again/ http://jamaica-gleaner.com/article/lead-stories/20150807/drought-affecting-lives-across-caribbean http://www.washingtontimes.com/news/2015/aug/5/parched-caribbean-faces-widespread-drought-water-s/?page=all http://jamaica-gleaner.com/article/lead-stories/20150706/st-thomas-struggles-cope-water-crisis http://www.jamaicaobserver.com/news/Drought-fuels-bush-fires-in-Manchester



Belize Millions $ losses in agriculture.

Cuba most severe drought since 2004 with water deficits in 45% of country and 100,000 people depending on water delivery by tanks.

Dominican Republic 11% decrease in agricultural production.

Guyana Guyana Water Inc. updated water rationing and management practices for Georgetown

Haïti 200,000 families affected by ongoing drought, with a 30% reduction in harvest over 2015

Puerto Rico streamflows well below average, eastern PR under drought, rationed water supply to San Juan up till October. (PR Met Service)

Potworks Dam in Antigua

Mona reservoir in Jamaica

Carraizo reservoir in Puerto Rico

https://anumetservice.wordpress.com/2015/08/17/antigua-is-out-of-surface-water-again/ http://jamaica-gleaner.com/article/lead-stories/20150807/drought-affecting-lives-across-caribbean http://www.washingtontimes.com/news/2015/aug/5/parched-caribbean-faces-widespread-drought-water-s/?page=all http://jamaica-gleaner.com/article/lead-stories/20150706/st-thomas-struggles-cope-water-crisis http://www.jamaicaobserver.com/news/Drought-fuels-bush-fires-in-Manchester


Our drought monitoring products E.g. the map below shows 12-month drought severity

between February 2015 and January 2015

LEGEND Source: Caribbean Drought Bulletin

Exceptionally Dry most severe very rare

Normal usual common

Exceptionally Wet most severe very rare

How do we know? OBSERVATIONS: • Short-term drought in

Lesser Antilles & Guyana. Medium- and long-term drought throughout the Antilles (except Cuba).

IMPLICATIONS: • Areas in short- to medium-

term drought: (i) more bush fires, (ii) low agricultural yields, (iii) possible price increase in local goods.

• Areas in long-term drought: (i) unreliable water supply due to water shortages & (ii) water consumption restrictions.

When can we expect drought relief?

El Niño subsiding El Niño weakening since December 2015; it is expected to

disappear by June 2016. AND: more likely than not, El Niño might make way for opposite:

La Niña.

Drought subsiding after dry season … BUT: As the 2015-6 dry season goes on, drought impacts will

worsen. AND: In case of La Niña, higher flood risk during the wet/Hurricane

season.

The current El Niño and drought to subside by June 2016

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North Atlantic Oscillation • NAO = interannual variability in winter (DJF) atmospheric circulation over North

Atlantic region defined by strength of gradient between semi-permanent Azores-Bermuda High & Iceland Low.

• NAO-index = normalized pressure difference between Azores & Iceland.

Predictability of rainfall and NAO: A positive NAO carries drier air to the Eastern Caribbean, in particular during the early part of the year, along with stronger trade winds. That means the east tends to be drier during positive NAO phases, and the opposite is true for negative phases, BUT: there is currently very limited predictability of the NAO itself. So even if we understand NAO influences rainfall, we can’t use it for seasonal forecasting.

NOAA CPC – NAO monitoring

Saharan Dust impacts our weather

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Dust interacts with radiation influences on the energy budget

Dust absorbs LW radiation warming of the layer these aerosols are located

Is transported through the globe in layers throughout the depth of the atmosphere

MJO Impacts on Caribbean


• MJO can cause ½ a month or more of enhanced convection or suppression of convection

• Should monitor its state and forecast and explain its impact to users

MJO & Hurricane Activity


Observed trends in temperature and rainfall extremes in the Caribbean

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EGU GA 2013 - Vienna Austria

Stephenson et al. (2014, Intl. J. Climatology)

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Significant region-wide temperature trends!!

increase TNmean +1.4°C

vs

TXmean +0.95°C

decrease in diurnal temperature range

(DTR).

a) TXmean

b) TNmean

c) DTR

1961-2010 1986-2010

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Significant region-wide temperature trends!! 1961-2010 1986-2010

a) TX90p

b) TX10p

c) TN90p

d) TN10p

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1961-2010 1986-2010

Increase in frequency of warm days (TX90p) and warm nights (TN90p) by >+15% & warming of warmest days and nights by +1°C Decrease in frequency of cold days (TX10p) -7% and cold nights (TN10p) by -10% & warming of coldest days and nights by +1°C

Significant region-wide rainfall trends?? a) PRCPTOT

b) SDII

c) CDD

1961-2010 1986-2010

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Despite recent apparent rise (boxed)

No annual RR change (PRCPTOT) No change in single rainfall event intensity (SDII) No change in dry spells (CDD)

a) R20mm

b) RX5day

c) R95p

Significant region-wide rainfall trends?? 1961-2010 1986-2010


No significant change in

RR from heavy rainfall events

Significant rise in extreme rainfall (R95p)

since about 1990

Comparison to previous assessment A similar workshop in 2001 resulted in a paper by Peterson et al. (2002,

JGR), noting: dramatic increase in # warm days and nights decrease in # very cool days and nights decrease in dry spell duration increase in # heavy rainfall events for a mean Caribbean.

Those results were calculated from 16 stations for TX/TN and 29 stations for RR running from 1958-1999, including data gaps.

All of their results except dry spell duration – no significant decrease – are corroborated by our findings.


Tight coupling land temperature

variability and Atlantic Multi-decadal Oscillation

(AMO)

Coupling very weak between rainfall and AMO

Decadal variability tied to AMO?

a) TX90p

d) SDII

b) TN90p

e) R50mm

c) TN10p

f) R50p



Take Home Messages The regional ETCCDI workshops continue to be a very efficient way of

rescuing climate data and updating our knowledge of climate trends and extremes.

Robust trends are: warming of mean and extreme daily maximum and minimum temperatures;

increase in number and temperature of very warm days and nights;

decrease in number and temperature of very cool days and nights.

Despite that models predict an increase in extreme precipitation, longer dry spells and reduced annual rainfall in the Caribbean, no long-term change is observed as yet…

… save for an emerging rising trend in extreme rainfall since 1990.

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Future Climate Change projections for the Caribbean

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Mean changes in the annual rainfall for 2071-2099 with respect to 1961-1989, as simulated by PRECIS_ECH and PRECIS_Had for SRESA2 and SRESB2.

Downscaled climate change projections for the end of 21st Century

(using IPCCC SRES scenarios)

- general drying trend for the Caribbean Basin

- Drying of 25% to 30%

- November to April possibly wetter far north

Climate Change

Adapted from: Taylor et al. (GFCS – Caribbean RWCS, Trinidad, 2013)

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EARLY WORKS – MODEL PROJECTIONS

Projected Precipitation Change

Drying exceeds natural variability

June-October – wet season drier!


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Projected Precipitation Change More recent climate change projections for the end of 21st Century

(using IPCCC RCP scenarios)

- same drying trend for the Caribbean Basin

- April to September likely drier

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hot hotter

Taylor et al. (2011)

Why?



Correlation of 925 zonal wind & Precipitation


more heating in east Pacific than in Caribbean more subsidence over Caribbean + stronger easterlies less rainfall

Munoz et al. 2008


Why?

Mean changes in the annual mean surface temperature for 2071-2099 with respect to 1961-1989, as simulated by PRECIS_ECH and PRECIS_Had for SRESA2 and SRESB2.

Warming by the end of 21st Century 1 to 5oC

Warming consistent with projections for other parts of globe.

Warming far exceeds natural variability

Projected Temperature Change


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More recent climate change projections for the end of 21st Century

(using IPCCC RCP scenarios)

Same conclusions as before

1oC to 5oC warming

Projected Temperature Change

Questions?

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regional climate variability and change · regional climate variability and change. 1 . ... source:...

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