Less rainfall expected for the Hawaiian Islands

Apr 23, 2013
This is rain in Hawaii. Credit: Gisela Speidel, International Pacific Research Center, University of Hawaii at Manoa

Almost imperceptibly, rainfall over the Hawaiian Islands has been declining since 1978, and this trend is likely to continue with global warming through the end of this century, according to a team of scientists at the University of Hawaii at Manoa (UHM) and the University of Colorado at Boulder. This latest Hawaii rainfall study, published in the March 13, 2013, early online issue of the Journal of Geophysical Research, supports previous work conducted at the University of Hawaii. What has been unclear, however, is whether this drying trend will continue.

"For water resource and ecosystem management, and for other societal needs, we need to know whether this drying trend will continue this century," says lead investigator Oliver Elison Timm at the International Pacific Research Center, UHM.

As of now, not even cutting edge have enough resolution to capture the diverse rainfall pattern over Hawaii, where dry and wet areas often lie only a mile or even less apart.

To work around this problem, the team devised a method called 'statistical downscaling.' They first got a take on the effects of the general drying trend on local heavy-rain days by reanalyzing observations from 1978 to 2010 at 12 rain-gauge stations spread throughout the islands. Studying hundreds of during such days, they identified the typical atmospheric circulation patterns in the North Pacific that favor heavy rains over Hawaii.

"The patterns we saw did not surprise us," recalls Elison Timm. "For example, we found that the typical winter Kona storms with moist air-flow from the South often produce torrential rains in the islands."

Using those weather patterns linked to , the team developed a statistical model that estimates the number of heavy rain events during a year. They found that the large circulation patterns over the mid-latitude and tropical North Pacific have already shifted since 1978 so that fewer weather disturbances reach the Islands during the rainy season from November through April.

"We can't predict individual rain events with our method," clarifies Professor Thomas W. Giambelluca, Department of Geography, UHM, "but it gives us a very good estimate of the number of heavy rain events in a given season based on the large-scale ."

Combining information from their and cutting-edge climate models driven with the projected increase in greenhouse gases until the end of this century, the scientists conclude that we can expect the recent trend towards drier winter seasons with fewer heavy-rain days to continue through the end of this century.

"It is extremely difficult to take all the uncertainties into account and our overall result may not apply to all sites in Hawai'i," cautions Senior Researcher Henry Diaz from the University of Colorado. "We are just beginning to understand the details of how climate change will affect the Hawaiian Islands. We do not know yet how further warming will impact extreme heavy downpours."

Explore further: Scientists stalk coastal killer

More information: Oliver Elison Timm, Mami Takahashi, Thomas W. Giambelluca, and Henry F. Diaz, 2013: On the Relation between Large-Scale Circulation Pattern and Heavy Rain Events over the Hawaiian Islands: Recent Trends and Future Changes. Journal of Geophysical Research, (early online-release in March 2013, onlinelibrary.wiley.com/doi/10… /jgrd.50314/abstract )

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User comments : 11

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antigoracle
1.7 / 5 (12) Apr 23, 2013
Another AGW Alarmist joke.
"Climate Scientists" conclude that they maybe wrong about an imperceptible change in rainfall, but let's blame global warming and preach gloom and doom.
deepsand
3 / 5 (12) Apr 24, 2013
A bigger denialist joke is to pretend that they know everything about everything.
antigoracle
1.4 / 5 (10) Apr 25, 2013
A bigger denialist joke is to pretend that they know everything about everything.

A sad truth, is the AGW Alarmist Zealots incredulous stupidity. So much so I must pretend that they have a brain.
Howhot
4.4 / 5 (7) Apr 25, 2013
I guess they will have to use Geothermal for desalination plants. All because of AGW. Someone need to put an Al-Gore cage around antigoracle. He's becoming over the top stupid.
deepsand
2.8 / 5 (11) Apr 26, 2013
A bigger denialist joke is to pretend that they know everything about everything.

A sad truth, is the AGW Alarmist Zealots incredulous stupidity. So much so I must pretend that they have a brain.

You do well to stop pretending to know and understand that which you are utterly ignorant of.
antigoracle
1.5 / 5 (8) Apr 27, 2013
A bigger denialist joke is to pretend that they know everything about everything.

A sad truth, is the AGW Alarmist Zealots incredulous stupidity. So much so I must pretend that they have a brain.

You do well to stop pretending to know and understand that which you are utterly ignorant of.
-- deepsand
Yes. I'm utterly ignorant of your level of stupidity and must stop pretending that I can understand it, because it's beyond human comprehension.
deepsand
2.6 / 5 (10) Apr 28, 2013
And, having now admitted your ignorance, perhaps you will shut up re. things that you do not understand.
antigoracle
1 / 5 (5) Apr 28, 2013
And, having now admitted your ignorance, perhaps you will shut up re. things that you do not understand.

Totally oblivious of its stupidity, the AGW Alarmist Zealot blindly supports the likes of its Vicar Gore, in his quest to be the first Carbon Credit/Tax billionaire.
deepsand
2.8 / 5 (9) Apr 29, 2013
AO, so long on rhetoric, yet so very short on substance.
antigoracle
1 / 5 (4) May 01, 2013
AO, so long on rhetoric, yet so very short on substance.

Says the AGW Alarmist who is incapable of comprehension.
deepsand
2.1 / 5 (7) May 01, 2013
AO, so long on rhetoric, yet so very short on substance.

Says the AGW Alarmist who is incapable of comprehension.

Are you a congenital liar or one of convenience of the moment?