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Examining Precipitation Patterns in the Pacific Islands

Map of 30-Year Mean Annual PERSIANN CDR Precipitation

In a collaborative effort between NASA and NOAA, participants from the NASA DEVELOP National Program used our PERSIANN Climate Data Record to create a climatology of long-term precipitation patterns in the U.S. Affiliated Pacific Islands.

Local weather service offices plan to use the results of this project to better understand how the different phases of the El Niño Southern Oscillation (ENSO) influence precipitation patterns on the Islands. Armed with this knowledge, the forecasters will also be able to better prepare their communities for extreme drought and heavy precipitation events.

The U.S. Affiliated Pacific Islands are highly susceptible to extreme precipitation events, such as drought and flooding, which directly affect their freshwater availability. Phases of ENSO predominately influence precipitation distribution in the region, and that distribution also differs by specific sub-regions. So, forecasters on the Islands currently rely on ENSO climatologies from sparse land-based station data to develop precipitation outlooks.

The NASA DEVELOP project provided forecasters with an updated ENSO-based climatology derived from both satellite and ground-based station observations. And, the project resulted in the creation of maps showing precipitation departures from average for each three-month season based on the Oceanic Niño Index for five ENSO phases: moderate–strong El Niño and La Niña, weak El Niño and La Niña, and neutral.

The PERSIANN Climate Data Record provided the participants with 30 years (1984–2015) of daily precipitation records, which they used to calculate monthly, seasonal, and yearly precipitation for the Exclusive Economic Zones encompassing American Samoa, Guam, the Republic of the Marshall Islands, the Federated States of Micronesia, the Commonwealth of the Northern Mariana Islands, the Republic of Palau, and Hawaii.

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