Who will chart the rain?

Raingage in Haleakalā, Maui. Photo credit: John DeLay

Anyone who lives in Hawai‘i knows that weather—or, more specifically, the likelihood of rain—is a very important part of everyday life, as evidenced by the sheer number of meteorologists and weather forecasters employed by local TV news stations. 

So it’s no surprise that one of the most frequently cited and referred to publications is the Rainfall Atlas of Hawai‘i, which was first published in 1986 by UH Mānoa Geography Professor Tom Giambelluca, Meteorology Professor Tom Schroeder and Michael Nullet, currently a Geography Research Assistant. The printed publication provided a set of maps of the spatial patterns of rainfall for the major Hawaiian Islands. 

Digital maps called rasters or grids were created based on the team’s analysis.

Fast forward 25 years, and Giambelluca is at it again. He, along with UH Mānoa Geography Assistant Professor Qi Chen and Masters’ student Abby Frazier, recently led a team of UH Mānoa researchers to create a new, interactive online website housing updated rainfall patterns. Giambelluca specializes in climate, climate change, and ecohydrology.

Developed to make rainfall maps, data and related information easily accessible, the website features high resolution downloadable digital maps for mean monthly and annual rainfall and uncertainty for each station used in the analysis, as well as files with information on each rain gage station. 

Mean Annual Rainfall for the State of Hawai‘i

Another unique component of the website is that it allows users to view the patterns of mean monthly and annual rainfall and corresponding uncertainty, zoom in on areas of particular interest, navigate to specific locations with the help of a choice of different base maps, and click on any location to get the mean annual rainfall and a graph and table of mean monthly rainfall. 

Over the course of the two-year project, rainfall measurements taken at over 1,000 stations were used as the principal source of information in the development of the rainfall maps. The maps represent the best estimates of the mean rainfall for the 30-year base period 1978-2007. However, for many reasons, it is not possible to determine the exact value of mean rainfall for any location. Therefore, for every map of mean rainfall, corresponding map of uncertainty is provided.

Knowledge of the mean rainfall patterns is critically important for a variety of meteorological, agricultural and resource management issues, including ground water and surface water development and protection, controlling and eradicating invasive species, protecting and restoring native ecosystems, and planning for the effects of global warming.  And, when you live in Hawai‘i and want to enjoy the outdoors as many days as possible, it’s simply invaluable.

To access the website, visit: http://rainfall.geography.hawaii.edu/.  Contact Giambelluca at thomas@hawaii.edu.

Top photo by Adam Levine/cogdog

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