Introduction to Global Climate and the Climate of the South Pacific Stakeholder Workshop Enhanced Application of Climate Predictions in Pacific Island Countries Vanuatu, Solomon Islands , Fiji, Tonga, Samoa, Niue, Cook Islands, Tuvalu, Kiribati 2005. Overview.
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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
Heat lost to space
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
Focus on the tropical belt
Heating from sun
West Pacific is usually warmer than the east
The warmest waters tend to follow the sun – so does the rain
Tropical weather is driven by where cloud and rainfall is favored. Generally, this is where the land or ocean is warmest => rainfall patterns are driven by changes in ocean temperatures.
January ocean temperatures
July ocean temperatures
Intertropical Convergence Zone
Dry east Pacific
South Pacific Convergence Zone
The Inter Tropical Convergence Zone
(also called the Equatorial trough)
The Climate of Suva – Fiji
More rainfall in summer when the ITCZ
The South Pacific Convergence Zone (SPCZ)
ITCZ tends to move
N to S
SPCZ tends to move
SW to NE
Focus of tropical convection can shift from west to east
Climate Variability Short and Long Term
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.
“Typical” SST pattern during an El Niño
Increasing sea surface temperatures (SSTs) across
the central and eastern Pacific
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.
Periods of rapid change
The typical cycle of El Nino
Period of slow change
Paths of Tropical Cyclones
El Niño years
La Niña years
Queensland Centre for Climate Applications
Source: Peter Hastings, University of Queensland
Central Pacific: 350mm in 2000 versus 1000mm in 1997
Severe western Pacific drought in 1997
Tracking El Niño
Tracking ENSO – The SOI
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.
Has shifted northeast in recent decades.
Possible signs include:
Hotter days and nights
Different rainfall patterns
Different timing of crops/flowers
Erosion of beaches and atolls
Different fish being caught
Tracking La Niña
Model Forecasts of El Niño/La Niña
Global climate is highly complex.
Day Time Temperatures
From: Griffiths et al (submitted to
International Journal of Climatology).
Night Time Temperatures
Thermocline: Layer of water between the warmer surface zone and the colder deep zone. In the thermocline, temperature decreases rapidly with depth.
Courtesy Neville Nicholls, BMRC
Ocean Currents of the World
Climate of Kampala, Uganda, Africa
ITCZ crosses twice – hence two rainfall peaks
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.
Gives rise to rainy spells – an active monsoon
Can trigger cyclone development
Can influence the development of El Niño