South Pacific rainfall in an era of warming: it's complicated

If complexity is the enemy of understanding, then oceanic rainfall patterns are plenty confusing.

A new study suggests that in a time of climate change, warming conditions can create conditions that both increase and decrease rainfall over Pacific Islands. 

(Image: Storms in the South Pacific. Credit: Digital Typhoon, National Institute of Informatics.)

If oceans are warmer, they pump more moisture into the atmosphere, creating the potential for more rain.

On the other hand, warming can reduce the difference in temperatures as you go deeper—and that can create drier weather—at least in certain areas of the southwest Pacific—by moving the rainy South Pacific Convergence Zone to the northeast.

Researchers  who built a model to try to make sense of this include Matthew J. Widlansky, Axel Timmermann, Karl Stein, Shayne McGregor, Niklas Schneider, Matthew H. England, Matthieu Lengaigne and Wenju Cai. Widlansky, Timmermann, Schneider and Stein are from the University of Hawai`i—the International Pacific Research Center and/or the Department of Oceanography.

What their model suggests is that which of the more-rain/less-rain paradigms wins out depends on how much warming there is. A couple of degrees of warming yields a slight drying trend; more than 3 degrees and the convergence zone gets wetter.

The South Pacific Convergence Zone is a band of clouds that bring moisture to a vast region of the South Pacific from the Solomon Islands to Tonga, Fiji and Samoa.

Timmermann, in a University of Hawai`i press release, describes the phenomenon of warming and rainfall like this:

“We have known for some time that rising tropical temperatures will lead to more water vapor in the atmosphere. Abundant moisture tends to bring about heavier rainfall in regions of converging winds such as the SPCZ.

“Nearly all climate change model simulations, however, suggest the equatorial Pacific will warm faster than the SPCZ region. This uneven warming is likely to pull the rainband away from its normal position, causing drying in the Southwest Pacific and more equatorial rainfall.”

The abstract for the researchers’ paper describes their result: “On the basis of a multi-model ensemble of 76 greenhouse warming experiments and for moderate tropical warming of 1–2 °C we estimate a 6% decrease of SPCZ rainfall with a multi-model uncertainty exceeding ±20%. For stronger tropical warming exceeding 3 °C, a tendency for a wetter SPCZ region is identified.”

For the islands of the South Pacific, who have complained bitterly about world inaction on climate change, the results are problematic. They are once again at the whim of the climate, with little ability to impact their own fate.

© Jan TenBruggencate 2012

The dying Hawaiian trades now a long-term trend

The northeast trade winds are among the key features of Hawai`i’s excellent weather, but new research shows that the trade winds are declining.

(Image: Trade winds directly impact cloud and wind patterns in the Hawaiian Islands, as here, on O`ahu. Credit: Chris Ostrander, UHM/SOEST.)

The change is dramatic. Winds measured at Honolulu Airport over the past 38 years show that the average number of northeast trade wind days annually has dropped 28 percent, from 291 to 210 days a year.

That has massive impacts, not only for human comfort levels, but for the environment. Cloud formation and rainfall patterns are changing with the altered wind patterns.

Four professors at the University of Hawai`i School of Meteorology published the new study. They are Jessica A. Garza, Pao-Shin Chu, Chase W. Norton and Thomas A. Schroeder. The study is “Changes to the prevailing trade winds over the islands of Hawaii and the North Pacific,” in the Journal of Geophysical Research. The abstract is here.

They based their work on their review of 37 years of wind speed and direction data from both land and sea-based stations on and around the Hawaiian Islands. As one might expect, since the northeast trades affect so much of our climate, that reduce trade weather has had an impact.

“We have seen more frequent drought in the Hawaiian Islands over the last 30 years. Precipitation associated with the moisture-laden northeasterly trades along the windward slopes of the islands contributes much of the overall rainfall in Hawaii,” Chu said.

The new study builds on previous work that had similar findings. In 2007, the journal on Climate published a paper, “Global Warming and the Weakening of the Tropical Circulation,” by Gabriel Vecchi of the NOAA Geophysical Fluid Dynamics Laboratory and Brian Soden of the Rosenstiel School for Marine and Atmospheric Science at the University of Miami. That paper is here.

While the Garza-Chu study covers actual field-collected data, the Vecchi study deals with models of a warming atmosphere. They came up with similar results. Vecchi summarized: “All models simulated a weakening of the convective overturning of mass in the atmosphere as the climate warmed.”

A 2010 briefing paper by University of Hawai`i coastal geologist Chip Fletcher, of the School of Ocean and Earth Science and Technology, makes the case linking climate change and the observed changes around Hawai`i:

“Hawai‘i’s climate is changing in ways that are consistent with the influence of global warming. In Hawai‘i:  air temperature has risen; rainfall and stream flow have decreased; rain intensity has increased; sea level and sea surface temperatures have increased; and, the ocean is acidifying,” Fletcher wrote.

In urging Hawai`i to move aggressively to study and plan for the changes, Fletcher minced no words: “Scientists anticipate growing impacts to Hawai‘i’s water resources and forests, coastal communities, and marine ecology.”

© Jan TenBruggencate 2012

Portugal a renewable powerhouse

LISBOA, Portugal -- Portugal has significant national economic issues, but it is one of the most aggressive nations in the world in renewable energy.

And many of its power sources are ones being deployed or considered for Hawai`i.

The hills around the capitol of Lisboa (Lisbon) are festooned with modern wind generators, which spin alongside traditional ancient Portuguese grain-grinding windmills (moinho de vento).   

(Image: A traditional Portuguese windmill alongside a new wind generator west of Lisboa. Jan TenBruggencate photo.)

The nation has more than 4,000 megawatts (4 gigawatts) of wind power installed on land. (Europe as a whole just passed the 100 gigawatt of wind milestone. By comparison, the U.S. has about 48 gigawatts of installed wind.)

 

There is a WindFloat wind turbine spinning offshore, developed by Principle Power. It is fitted with a Vestas V80 2 megawatt wind turbine, and the stable platform is anchored to the seafloor. 

A seafloor wave energy device, WaveRoller , is deployed on the ocean floor off Peniche. It was designed and built by the Finnish firmAW-Energy Oy. Three 100-kilowatt units are operating.

Another wave energy device was installed at the Aguçadoura Wave Farm near Porto, but has been brought back to harbor for repairs to its bearings.  It uses a Scottish-designed Pelamiswave generator.

The Portuguese Alto Lindoso reservoir has an immense hydroelectric capacity of 630 megawatts, and there are 100 or so other hydroelectric plants in the country. The Portuguese utility Energias de Portugal is currently building six new hydro plants.

The nation has more than 140 megawatts of installed solar photovoltaic generation, including the 46-megawatt Amareleja array, one of the world’s largest.  

With all that, Portugal has a problem. While nearly half of its electricity comes from renewables, there are times at night when Portugal has more renewable power than it has demand.

A white paper for the European Commission notes that renewables have grown throughout Europe far faster than government planners anticipated. 

Planners have tried to address these oversupply issues in several ways. One is to find export markets for the power.

One of other solutions for Portugal is something called pumped storage. Pumped storage, which has been discussed in Hawai`i, involves pumping water uphill when power is plentiful, and then running it back down through hydroelectric generators when the power is needed.

Energias de Portugal is building a 192-megawatt pumped storage facility, Frades II, on the Cávado River in the north Portugal Braga region. It is one of several Energias de Portugal pumped storage facilities in the works. Another is a 240 megawatt facility on the Tua River, which flows into the Douro. 

Still another, although longer-term, solution to the night-time oversupply problem is electric vehicles. If that extra power could be used to charge electric cars at night, it could both reduce fossil fuel use and smooth out the power demand curve.

Of course, issues like a global economic crisis throw the best-laid plans into chaos. In the midst of its economic issues, the government of Portugal has blocked spending on new renewable energy projects, with the exception of hydropower and co-generation. But it is a nation with a significant renewable energy program, one that is like to serve it well into the future.

© Jan TenBruggencate 2012

Millerbird magic: heroic second translocation effort succeeds

A second group of Nihoa millerbirds has been successfully moved from Nihoa to Laysan—both islands in the northwestern end of the Hawaiian archipelago.

The movement assures the species of a second breeding population, improving its potential for survival.

 

(Image: Millerbirds handed down the slope of rocky Nihoa Island. Credit: USFWS.)

Biologists collected, shipped by boat from Nihoa to Laysan, and released 26 millerbirds in mid-August, in a joint effort of the U.S. Fish and Wildlife Service (FWS), American Bird Conservancy (ABC), and other organizations. Twenty-four millerbirds were moved to the island in 2011, and those first birds have already produced 17 chicks.

“So far, everything has gone extremely well for the birds,” said millerbird expert and University of Hawai`i biologist Sheila Conant. “They were captured without incident; they made it through the boat ride in good health; we had no problems attaching transmitters to them; and they have now been released to their new habitat without a hitch.  So we are thrilled with the way this phase has gone.”

 

 (Image: Photographer captures the release of millerbirds in the green fields of flat Laysan Island. Credit: Sheldon Plentovich, USFWS.)

Millerbirds eat insects. The little (one-ounce) birds forage in the low shrubs and bunchgrasses of the islands. They are relatives of a class of birds known as old world warblers. BirdLife International has more information here.

This species is not new to Laysan. A subspecies, the Laysan millerbird, existed on Laysan until introduced rabbits helped denude the island of much of its vegetation, and the habitat destruction killed off the birds. Laysan’s rabbits have long since been removed and the native vegetation is being restored.

(Image: A millerbird on Laysan with a fresh spider in its bill. Credit, John Vetter, USFWS.)

Scientists are assuming that the 50 birds translocated in the 2011 and 2012 projects will provide a sufficient founder population to allow a healthy self-sustaining population to develop, said Don Palawski, Acting Fish and Wildlife Service Superintendent of the Papahānaumokuākea Marine National Monument, which encompasses the Northwestern Hawaiian Islands.

Work during the first year of Nihoa millerbird presence on Laysan suggests that the habitat is appropriate for them, and there is sufficient food. 

Laysan is an extremely isolated island, without an airfield or harbor. Researchers arrive at the island on small boats from research vessels anchored offshore. Winter access is generally not possible due to surf, but one researcher will remain on the island through the winter season to keep tabs on the birds.

The Fish and Wildlife Service web page on its millerbirdwork is here.

© Jan TenBruggencate 2012

Tatooine-Prime is not alone: binary planets around binary suns

The University of Hawai`i managed to write about the discovery of planets around a binary star system without once mentioning the iconic planet, Tatooine.

Partly, that might be because there is far more about the new discovery than just the fact that a planet exists around two stars spinning in their own tight orbit. In this case, two planets (maybe three) around the two stars.

(Image, an artist’s view of a planet like Tatooine, with its twin suns spinning in the distance. This system, spotted through the Kepler spacecraft, is called Kepler-47. Credit: NASA/JPL-Caltech/T. Pyle)

Tatooine, of course, is the desert planet in the Star Wars film series, which is the home planet to both Anakin and Luke Skywalker. In many of its scenes, Tatooine’s twin suns are displayed above the horizon.

University of Hawai`i astronomer Nader Haghighipour was part of a team that discovered what they called Kepler-47, naming it after the Kepler space observatory, which was launched in 2009.  The funding for the team’s work came from NASA and the National Science Foundation.

The team announced the finding at the triennial International Astronomical Union meeting in Beijing, and published it in Science—under the daunting title: “Kepler-47: A Transiting Circumbinary Multiplanet System.” The abstract is here. 

What’s cool about this?

Binary star systems are cool, although this is not the first one that’s been found.

That this binary star system has a complement of planets is cool—first time that’s been seen. It proves that it’s possible for a solar system to exist around twin suns. The stars of Kepler-47 orbit each other roughly weekly—every 7.5 days.

And ultimate cool for science fiction fans and astronomers is one of the planets is within the stars’ habitable zone, meaning liquid water could exist on their surfaces. The question still unanswered is whether this planet even has a surface on which to have liquid water. It could be a gas giant like Jupiter—but maybe not.

The inner planet is smaller, three times Earth’s radius, and spins a full orbit around its suns in 49 days. The other—the one in the habitable zone—is Jupiter-sized at 4.6 times Earth’s radius and orbits every 303 days—not far from Earth’s 365.

And there may be a third planet, although the evidence isn’t yet strong enough to say for sure.

Here is the University of Hawai`i Institute for Astronomyrelease, with links and images. 

© Jan TenBruggencate 2012