Nav: Home

New research shows La Niña is not helping Hawai'i's rainfall and groundwater

November 12, 2015

Historically when El Niño events occur, Hawai'i has experienced nearly six months of drought, from November to April. Conversely, during La Niña events rainfall has been greater than normal - building up Hawai'i's groundwater supply. New research published this month in the Journal of Climate by scientists at the University of Hawai'i - Mānoa, Nanjing University of Information Science and Technology, and NOAA's Honolulu National Weather Service (NWS) Office, determined that the relationship between La Niña and rainfall in Hawai'i has changed and recent La Niña years have brought less-than-normal rainfall.

Because the La Niña events have brought excess rainfall to the State in the past, the new information indicating decreased rainfall during recent La Niña events has important implications for agriculture, water resource management, and more.

"Initially, this changing relationship between La Niña and Hawaii rainfall was brought to my attention by Kevin Kodama [co-author of the paper and hydrologist at NOAA's Honolulu NWS]," said co-author Pao-Shin Chu, professor of Atmospheric Sciences at UHM School of Ocean and Earth Science and Technology and Hawai'i State Climatologist. "However, we had no idea when this shift occurred, nor any comprehensive analysis to understand the mechanisms for this change."

Chu and co-authors analyzed data from 50 rain gauges managed by the National Weather Service (NWS) throughout the State, which provided rainfall measurements from 1956 to 2010. A statistical analysis, called a changepoint analysis, determined that the shift - from excess rainfall to less-than-normal rainfall - during in La Niña years occurred in 1983.

The researchers then compared factors affecting weather and climate between the two periods on either side of that shift - 1956 to 1982 and 1983 to 2010. This comparison uncovered changes in the large-scale atmospheric circulation patterns before and after the shift.

The strengthening, broadening, and westward shifting of the eastern North Pacific subtropical high-pressure system, coupled with an eastward elongation and intensification of the subtropical jet stream were found to be influential in reducing rainfall during the recent La Niña seasons.

Additionally, assessing storm-track data revealed that the changes found in the aforementioned circulation features created a less favorable environment for the development of Kona low-pressure systems and fronts in the vicinity of Hawai'i. Variability in tropical sea surface temperatures and circulation features in the northern Pacific Ocean have also changed during La Niña wet seasons - further forcing the changes in La Niña-year rainfall.

"In the future, it may be possible to use a regional climate model to shed more light on the variability of rainfall in Hawai'i," said Chu.
-end-


University of Hawaii at Manoa

Related Rainfall Articles:

NASA looks at rainfall from Tropical Storm Dora
Now a tropical storm, Hurricane Dora has been skirting southwestern Mexico's coast since it formed and has transported tropical moisture onshore that has produced some heavy rain showers.
NASA adds up Tropical Storm Cindy's rainfall
Tropical storm Cindy was downgraded to a tropical depression after moving onshore near the Texas and Louisiana Border on Thursday June 22, 2017 and bringing a lot of rain with it.
Bangladesh's heavy rainfall examined with NASA's IMERG
At least 156 people in Bangladesh were killed during the past week by landslides and floods caused by heavy rainfall.
NASA looks at extreme Florida rainfall by satellite
Extremely heavy rain has recently fallen over Florida and the Global Precipitation Measurement or GPM mission core satellite looked at that some of that rainfall on June 7.
Summer rainfall in vulnerable African region can be predicted
Summer rainfall in one of the world's most drought-prone regions can now be predicted months or years in advance, climate scientists at the Met Office and the University of Exeter say.
NASA adds up record Australia rainfall
Over the week of May 15, extreme rainfall drenched northeastern Australia and NASA data provided a look at the record totals.
Varied increases in extreme rainfall with global warming
A new study by researchers from MIT and the Swiss Federal Institute of Technology in Zurich shows that the most extreme rain events in most regions of the world will increase in intensity by 3 to 15 percent, depending on region, for every degree Celsius that the planet warms.
NASA examines Peru's deadly rainfall
The Global Precipitation Measurement mission or GPM constellation of satellites provide data on precipitation rates and totals.
NASA examines Ex-Tropical Cyclone Dineo's rainfall
NASA examined the heavy rainfall generated by Tropical Cyclone Dineo as it made landfall in Mozambique and NASA's Terra satellite spotted the storm's remnants over four countries.
NASA observes extreme rainfall over Southern California
NASA calculated California's rainfall over seven days using a constellation of satellites and created a map to provide the visual extent of the large rainfall totals.

Related Rainfall Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...