When El Nino Rages: How Satellite Data Can Help Water-Stressed Islands

The United States Affiliated Pacific Islands (USAPI) are highly susceptible to extreme precipitation events such as drought and flooding, which directly affect their freshwater availability. Precipitation distribution differs by sub-region, and is predominantly influenced by phases of the El Niño Southern Oscillation (ENSO). Forecasters currently rely on ENSO climatologies from sparse in situ station data to inform their precipitation outlooks. To address this spatial gap, a unique NOAA/NASA collaborative project updated the ENSO-based rainfall climatology for the Exclusive Economic Zones (EEZ’s) encompassing Hawaii and the USAPI using NOAA’s 15km PERSIANN Climate Data Record. This data provided a 30-year record (1984-2015) of daily precipitation at 0.25° resolution, which was used to calculate monthly, seasonal, and yearly precipitation average. The 478-page satellite-derived reference atlas not only illustrates the long-term average rainfall distribution by month, but also shows the percent departure from average for each three-month season based on the Oceanic Niño Index (ONI) for weak, moderate, and strong ENSO phases. Local weather service offices are already using the atlas to better understand precipitation patterns across their regions, and as such are able to produce more accurate forecasts during different ENSO phases to inform adaptation, conservation, and mitigation options for drought and flooding events. The presentation will showcase the development of the atlas, highlight some of the challenges encountered, and demonstrate how CDRs can be used to inform decision-making.