Pacific Island Global Climate Observing System basic instrument project: High quality tipping bucket raingauges

The Pacific Island Global Climate Observing System (PI-GCOS), a component of the GCOS world wide program, is striving to implement several objectives outlined in the PI-GCOS action plan. One of these projects is for the enhancement and expansion of basic climate observations to be taken throughout the Pacific, particularly on remote islands. Given the Pacific's vastness and the countries' limited capacity to manually operate a sustainable climate network, a pilot project was recently completed using very high quality tipping bucket raingauges installed with HOBO data loggers. These gauges were designed, built, and calibrated in collaboration with the University of Oklahoma and the METONE Instrument Corporation.

Eight gauges have been installed and are operating in the countries of Niue, Samoa, Tonga, and Vanuatu. The instruments and data gathered are the property of the respective countries' meteorological service. The project is being carried out by climate officers from these same meteorological services.

To test the accuracy and reliability of these gauges, manual-read 4-inch gauges have been set up within a 15-foot radius of the tipping bucket gauge, and at the same height. The tips are recorded and converted into daily rainfall that is then compared to the manual gauges.

The result of nearly a year's worth of data show that the 12-inch tipping gauges match very well with the manual gauges, with the exception of periods of extremely high rain events. During these events, the tipping buckets indicate higher rain amounts than the manual gauges. In some locations there are two manual gauges located near the tipping bucket gauge. During high rainfall rates, the two manual gauge measurements are nearly identical.

Due to the pilot project's success, 55 additional tipping gauges will be distributed to these and other Pacific Island countries on an as-needed basis. This project is being funded by the US National Oceanic and Atmospheric Administration and managed in collaboration with the New Zealand Meteorological Service PI-GCOS Technical Support Project (i.e. PI-GCOS TSP), the Pacific Island meteorological services, the University of Oklahoma and the Secretariat for the Pacific Regional Environmental Programme.