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Project ID: GU1342

Title: Development of Monthly and Seasonal Rainfall Climatologies and Distribution Maps for Guam

Focus Categories: Hydrology, Climatological Processes

Keywords: Climate, Rainfall, Data Analysis, Atmospheric Processes, Remote Sensing

Start Date: 03/01/2001

End Date: 02/28/2002

Federal Funds: $16,919

Non-Federal Matching Funds: $0

Congressional District: N/A

Principal Investigators:
Charles Guard
Research Associate, University of Guam

Mark Lander
Assistant Professor, University of Guam


Guam is characterized by one of the highest levels of rainfall variability in the world. Much of this variability can be traced to inter-annual climate variability and to typhoon and monsoon events. The high rainfall variability and complex distribution directly affect ground and surface water supplies, water quality, erosion, pollution from run-off, and local flooding. While historically, there have been some rainfall distribution studies accomplished for Guam, these studies have been based on very limited databases and have significantly oversimplified the magnitude and orientation of rainfall gradients across the island. A recent USGS 104b study conducted at the Water and Environmental Research Institute (WERI), University of Guam (UOG), using an extended and updated 50-year rainfall database, meteorological satellite data, and Doppler radar data, illustrated the complexness of the annual rainfall distribution over Guam. The PI developed the 50-year database by acquiring original data sources to expand normally available commercial and climatological databases. Many hydrological studies require an accurate depiction of the rainfall distribution over the region of interest.

This study will update the 50-year database with additional data that has become available. From that data, the investigators will update the annual rainfall distribution analysis, which is derived from a composite of the 50 individual annual analyses. The composite data are rainfall values extracted from 150 locations on each of the annual analyses. A similar process will be applied to derive monthly and seasonal rainfall distribution maps and average values. Satellite and radar data, where available, are used to estimate rainfall distribution over the oceanic periphery of the island, and to verify the favored behavior of rainfall systems across the island. If time permits, the study will also include analyses of El Nino and La Nina rainfall patterns.

The objective of the study is to provide a set of accurate and complete monthly and seasonal (rainy season, dry season) rainfall distribution maps for Guam. These maps can then be used for a multitude of hydrological studies and as a realistic verification source for rainfall modeling studies planned for the island. Results of the study will be published as a WERI Technical Report.

Progress/Completion Report PDF

U.S. Department of the Interior, U.S. Geological Survey
Maintained by: John Schefter
Last Updated: Thursday June 24, 2004 3:18 PM
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