Tuvalu Meteorological Service

The meteorological office on Funafuti was established in 1951 under the auspices of the South Pacific Air Transport Council (SPATC).[5] An upper air observation programme was established in 1960. After the dissolution of SPATC in 1979, the Meteorological Service of New Zealand Limited supported the upper air programme until the TMS assumed responsibility for the programme, with continuing support by the New Zealand Ministry of Foreign Affairs and Trade (MFAT)/NZAID.[5] The TMS works with the New Zealand MetService, the Fiji Meteorological Service, the Australian Bureau of Meteorology, Geoscience Australia, the United States Geological Survey and the National Weather Service.[6]

Ms Hilai Vavae retired as Director of the Tuvalu Met Service in 2014.[7]

Sea surface temperature anomalies in November 2007 showing La Niña conditions. Blue=temperature below average; red=temperature above average

Tuvalu participates in the operations of the Secretariat of the Pacific Regional Environment Programme (SPREP).[8] The climate of the Pacific region at the equator is influenced by a number of factors; the science of which is the subject of continuing research. The SPREP described the climate of Tuvalu as being:

[I]nfluenced by a number of factors such as trade wind regimes, the paired Hadley cells and Walker circulation, seasonally varying convergence zones such as the South Pacific Convergence Zone (SPCZ), semi-permanent subtropical high-pressure belts, and zonal westerlies to the south, with the El Niño–Southern Oscillation (ENSO) as the dominant mode of year to year variability (…). The Madden–Julian oscillation (MJO) also is a major mode of variability of the tropical atmosphere-ocean system of the Pacific on times scales of 30 to 70 days (…), while the leading mode with decadal time-scale is the Interdecadal Pacific Oscillation (IPO) (…). A number of studies suggest the influence of global warming could be a major factor in accentuating the current climate regimes and the changes from normal that come with ENSO events (…).[9]

The sea level in Tuvalu varies as a consequence of a wide range of atmospheric and oceanographic influences. The 2011 report of the Pacific Climate Change Science Program published by the Australian Government,[10] describes a strong zonal (east‑to-west) sea-level slope along the equator, with sea level west of the International Date Line (180° longitude) being about a half metre higher than found in the eastern equatorial Pacific and South American coastal regions. The trade winds that push surface water westward create this zonal tilting of sea level on the equator. Below the equator a higher sea level can also be found about 20° to 40° south (Tuvalu is spread out from 6° to 10° south). The Pacific Climate Change Science Program Report (2011) [11] describes the year-by-year volatility in the sea-level as resulting from the El Niño–Southern Oscillation (ENSO):

ENSO has a major influence on sea levels across the Pacific and this can influence the occurrence of extreme sea levels. During La Niña events, strengthened trade winds cause higher than normal sea levels in the western tropical Pacific, and lower than normal levels in the east. Conversely, during El Niño events, weakened trade winds are unable to maintain the normal gradient of sea level across the tropical Pacific, leading to a drop in sea level in the west and a rise in the east. Pacific islands within about 10° of the equator are most strongly affected by ENSO‑related sea-level variations."[11]

The Pacific (inter-)decadal oscillation is a climate switch phenomenon that results in changes from periods of La Niña to periods of El Niño. This has an effect on sea levels. For example, in 2000 there was a switch from periods of downward pressure of El Niño on sea levels to an upward pressure of La Niña on sea levels, which upward pressure causes more frequent and higher high tide levels. The Perigean spring tide (often called a king tide) can result in seawater flooding low-lying areas of the islands of Tuvalu.[12]

The purpose of the meteorological programmes operated by the TMS is to gather data in the tropical western Pacific so as to work to achieve “accurate production of weather forecasts, seasonal and interannual climate forecasting (ENSO predictions), and understanding changes in climate and sea level for Tuvalu and its neighbouring Pacific Islands. Tuvalu lies across a known development region for tropical cyclones and ENSO activity. It provides crucial data to global weather, climate modelling and forecasting centres. It also provides the key data used for tropical cyclone and ENSO forecasting.”[5]

Upper air observations

A radiosonde shortly after launch.

The upper air observation programme in Funafuti makes radiosonde observations to collect upper air weather for weather forecasting and research. The radiosonde observations use a small, expendable instrument package is suspended below a 2 metres (6.6 ft) wide balloon filled with hydrogen or helium. As the radiosonde rises at about 300 meters/minute (1,000 ft/min), sensors on the radiosonde measure profiles of pressure, temperature, and relative humidity. These sensors are linked to a battery-powered radio transmitter that sends the sensor measurements to a ground receiver. By tracking the position of the radiosonde in flight, information on wind speed and direction are also obtained.

The data is shared with Regional Specialized Meteorological Centers (RSMCs) in Nadi, Wellington, Brisbane, Melbourne and Honolulu. The weather modelling carried out by the RSMCs enables more accurate forecasts to be prepared for Tuvalu and for the tropical western Pacific.[5]

TMS participates in the activities of:

• The World Meteorological Organization (WMO).
• The South Pacific Applied Geoscience Commission (SOPAC).
• The Secretariat of the Pacific Regional Environment Programme (SPREP).
• SOPAC / SPREP / WMO sponsored meetings of Regional Meteorological Service Directors and Regional Disaster Managers.
• The Pacific Meteorological Council (PMC): is a specialized subsidiary body of SPREP, established in July 2011 at the 14th Regional Meteorological Services Directors meeting in Majuro, Marshall Islands on a bi-annual basis to facilitate and coordinate the scientific and technical programme and activities of the Regional Meteorological Services.[22]
• The Online Climate Outlook Forum (OCOF): also known as the Pacific Islands online Climate Outlook Forum (PICOF) that is a monthly discussion among Pacific Island National Meteorological Services (NMS) and the Australian Bureau of Meteorology. The OCOF assists in the implementation of the SCOPIC project and the Climate Adaptation Projects that are supported by the Australian Bureau of Meteorology.[20]

• Geography of Tuvalu
• Climate change in Tuvalu
• 2011 Tuvalu drought