Introduction to Global Climate and the Climate of the South Pacific Stakeholder Workshop Enhanced Ap

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Introduction to Global Climate and the Climate of
the South PacificStakeholder Workshop Enhanced
Application of Climate Predictions in Pacific
Island Countries Vanuatu, Solomon Islands,
Fiji, Tonga, Samoa, Niue, Cook Islands, Tuvalu,
Kiribati2005
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Overview

• Introduction to Global and Pacific weather and
  climate
• Intertropical Convergence Zone, South Pacific
  Convergence Zone
• Climate variability in the South Pacific
• Climate change in the South Pacific

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The Driver for Weather and Climate is Heating
from the Sun
Heat lost to space

• Highly simplified (assumes earth is not rotating)
• Result
• Low pressure at the equator
• High pressure at poles
• All weather and climate is driven by this energy
  imbalance this is essentially a global sea
  breeze effect

Heat from sun
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The Global Circulation The Effect of the
Earths Rotation

• Rising motion triggering rain and cloud in the
  tropics (same as in the no-rotation case)
• Sinking motion in the subtropics deserts.
• Mid latitude cyclones around 60º.

Heating from sun
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Climate of the Tropics and South Pacific
Tropical weather is driven by where cloud and
rainfall is favored. Generally, this is where the
land or ocean is warmest gt rainfall patterns are
driven by changes in ocean temperatures.
January ocean temperatures
July ocean temperatures
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Rainfall in the Tropics(mm/day)
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Climate of the South Pacific
Intertropical Convergence Zone
Dry east Pacific
South Pacific Convergence Zone
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The Inter Tropical Convergence Zone (also called
the Equatorial trough)

• A zone of high rainfall and much cloudiness
• A zone of convergence of the trade winds
• Moves north and south with the seasons
• Can have ragged edges or spurs

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The Climate of Suva Fiji More rainfall in
summer when the ITCZ is closest.
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The South Pacific Convergence Zone (SPCZ)

• The largest and most persistent spur of the
  ITCZ a belt of high rainfall and cloudiness
• Stretches from the Solomon Islands to Fiji, Samoa
  and Tonga
• Associated with a sea surface temperature maxima
• Is present year round but most active in the
  Southern Hemisphere summer

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Climate Variability in the South Pacific
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Climate Variability Short and Long Term
Climate variability affecting the South
Pacific Seasonal variations (ITCZ and
SPCZ) Interannual variations (El Niño/La
Niña) Long-term Climate Change Climate change
and Climate Variability are not the same.
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The El Niño Southern Oscillation (ENSO)
We are interested in El Niño because it is the
dominant driver of natural climate
variability. El Niño refers to a broad scale
warming of water in the central and eastern
tropical Pacific Ocean (remember rain tends to
occur over the warmest waters). They tend to
occur every 3 to 7 years e.g., 1994, 1997,
2002. La Niña is the reverse of El Niño.

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Typical SST pattern during an El Niño
Increasing sea surface temperatures (SSTs) across
the central and eastern Pacific
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The Impact of El Nino and La Nina
The changes in ocean temperatures associated with
El Niño and La Niña, cause large changes in
rainfall. Also, El Niño and La Niña can be
predicted, and so their impacts can also be
predicted.

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The typical cycle of El Nino

Period of slow change higher predictability
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Paths of Tropical Cyclones
El Niño years
La Niña years
Slide 21.10 Queensland Centre for Climate
Applications
Source Peter Hastings, University of Queensland
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1997 an El Nino - 2000 a La Nina (mm/day)
Central Pacific 350mm in 2000 versus 1000mm in
1997 Severe western Pacific drought in 1997
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Tracking El Niño

• Indicators for an El Niño include
• The Walker Circulation and trade winds weaken.
• The warm pool region moves east towards the
  central Pacific - ocean temperatures become
  warmer than average in the central and eastern
  Pacific.
• The SOI remains negative for several consecutive
  months.
• Cloud and rainfall increase over the central and
  east Pacific. Decreases in the west - over
  Australia, Indonesia, Solomon Islands etc.
• La Niña is largely the opposite.

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Tracking ENSO The SOI
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Global Climate Change

• Global observations show that the climate is
  changing
• Temperatures are generally warming.
• Rainfall patterns have changed. Some places are
  wetter, some drier.
• Climate extremes have change. More hot days and
  hot nights.
• These changes are very likely to continue.
• The major cause for many of these changes are
  human influences.

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Global Temperature Increase
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Local Climate Change

• South Pacific Sea Level Monitoring Project
• Aim is to "Provide an accurate long term record
  of sea levels in the South Pacific
• Initiated in 1991
• 14 countries involved

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South Pacific Convergence Zone
Has shifted northeast in recent decades.
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Climate Change in Your Country?

• Are there signs of change in your country?
• Possible signs include
• Hotter days and nights
• Different rainfall patterns
• Different timing of crops/flowers
• Coral Bleaching
• Erosion of beaches and atolls
• Different fish being caught

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Future Climate Local Changes

• Climate Change Projections from a single model
• Short lead 2025-2034 minus model 1961-1990

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Further Information

• Your local Meteorological Service
• The internet
• http//www.bom.gov.au/climate/pi-cpp/
• http//www.wmo.ch
• http//iri.columbia.edu/climate/forecast
• http//www.ipcc.ch

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Thank You
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Tracking La Niña

• Indicators for a La Niña include
• The Walker Circulation and trade winds
  strengthen.
• The warm pool moves west towards Indonesia -
  ocean temperatures become cooler than average in
  the central and eastern Pacific.
• The SOI remains positive for several consecutive
  months.
• Cloud and rainfall decrease over the central and
  east Pacific. Increase in the west - over
  Australia, Indonesia, Solomon Islands etc.

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Model Forecasts of El Niño/La Niña
El Niño
La Niña
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Climate Processes
Global climate is highly complex.
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Local Climate Change
Day Time Temperatures
From Griffiths et al (submitted to
International Journal of Climatology).
Night Time Temperatures
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NOAA Image
Thermocline Layer of water between the warmer
surface zone and the colder deep zone. In the
thermocline, temperature decreases rapidly with
depth.
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NOAA Image
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NOAA Image
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Spac winter
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Spac summer
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Courtesy Neville Nicholls, BMRC
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Ocean Currents of the World
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Climate of Kampala, Uganda, Africa ITCZ crosses
twice hence two rainfall peaks
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The Madden Julian Oscillation?
A progression of large regions of both
enhanced and suppressed rainfall that moves from
west to east mainly over the Tropical Indian and
Pacific Oceans. It is the dominant influence on
weather variations in the tropics.
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The MJO
Gives rise to rainy spells an active monsoon
Can trigger cyclone development Can influence
the development of El Niño