South Pacific Climate

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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 : 

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: 

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

The Driver for Weather and Climate is Heating from the Sun : 

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

The Global Circulation – The Effect of the Earth’s Rotation: 

The Global Circulation – The Effect of the Earth’s 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

Climate of the Tropics and South Pacific: 

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 => rainfall patterns are driven by changes in ocean temperatures. January ocean temperatures July ocean temperatures

Rainfall in the Tropics (mm/day): 

Rainfall in the Tropics (mm/day)

Climate of the South Pacific: 

Climate of the South Pacific Intertropical Convergence Zone South Pacific Convergence Zone Dry east Pacific

Slide8: 

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”

Slide9: 

The Climate of Suva – Fiji More rainfall in summer when the ITCZ is closest.

Slide10: 

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

Climate Variability in the South Pacific: 

Climate Variability in the South Pacific

Slide12: 

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.

Slide13: 

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.

Slide14: 

“Typical” SST pattern during an El Niño Increasing sea surface temperatures (SSTs) across the central and eastern Pacific

Slide15: 

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.

Slide16: 

The typical cycle of El Nino Period of slow change higher predictability

Slide19: 

Paths of Tropical Cyclones Slide 21.10 Queensland Centre for Climate Applications La Niña years El Niño years Source: Peter Hastings, University of Queensland

1997 an El Nino - 2000 a La Nina (mm/day): 

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

Slide21: 

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.

Slide22: 

Tracking ENSO – The SOI

Global Climate Change: 

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.

Global Temperature Increase: 

Global Temperature Increase

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 Local Climate Change

South Pacific Convergence Zone: 

South Pacific Convergence Zone Has shifted northeast in recent decades.

Climate Change in Your Country?: 

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

Future Climate – Local Changes: 

Future Climate – Local Changes Climate Change Projections from a single model: Short lead: 2025-2034 minus model 1961-1990

Further Information: 

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

Thank You: 

Thank You

Slide31: 

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.

Slide32: 

Model Forecasts of El Niño/La Niña El Niño La Niña

Climate Processes: 

Climate Processes Global climate is highly complex.

Local Climate Change: 

Local Climate Change Day Time Temperatures Night Time Temperatures From: Griffiths et al (submitted to International Journal of Climatology).

Slide36: 

NOAA Image Thermocline: Layer of water between the warmer surface zone and the colder deep zone. In the thermocline, temperature decreases rapidly with depth.

Slide37: 

NOAA Image

Slide38: 

NOAA Image

Spac winter: 

Spac winter

Spac summer: 

Spac summer

Slide41: 

Courtesy Neville Nicholls, BMRC

Slide42: 

Ocean Currents of the World

Slide45: 

Climate of Kampala, Uganda, Africa ITCZ crosses twice – hence two rainfall peaks

Slide46: 

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.

Slide47: 

The MJO Gives rise to rainy spells – an active monsoon Can trigger cyclone development Can influence the development of El Niño