Meteorologists investigate Airborne jet streams bringing both floods and drought relief

A satellite image showing water-vapour concentration reveals an atmospheric river (yellow) streaming northeast across the Pacific Ocean.

Californians call it the Pineapple Express: a weather pattern that zips across the Pacific Ocean from Hawaii, delivering not baskets of tropical fruit, but buckets of rain and snow.

In meteorological terms, the Pineapple Express is an atmospheric river, a narrow band of air that carries huge amounts of moisture.

For the next six weeks, meteorologists will be plying the eastern Pacific by air and sea, in the hope of catching several atmospheric rivers barrelling towards the coast.

It is the biggest push yet to understand these phenomena, which have received serious scientific attention only in the past decade.

Atmospheric rivers get their start over warm tropical waters; they then flow eastwards and towards the poles a kilometre or two above the ocean surface.

They may stretch for thousands of kilometres, but are only a few hundred kilometres wide. When they hit land, they start to drop their moisture in torrential downpours or blizzards.

“When we have too many atmospheric rivers, floods can occur, and when we don’t have enough we gradually fall into drought,” says Marty Ralph, a meteorologist at the Scripps Institution of Oceanography in La Jolla, California, and a leader of the field campaign.

In Europe, atmospheric rivers affect mostly the western part of the continent, but they can be felt as far inland as Poland.

In North America, the entire west coast is affected, and parts of the central and eastern United States occasionally feel the effects of atmospheric rivers that develop over the Gulf of Mexico.

The moisture is often welcome, bringing up to half of the year’s water supply in affected areas1.

A 2013 study found that as many as three-quarters of all droughts in the Pacific Northwest between 1950 and 2010 had been brought to an end by atmospheric-river storms2.

California has been stricken by drought for years (Nature 512, 121–122; 2014), but last month, an atmospheric river dropped enough rain to erase one-third of the water deficit of one major reservoir in just two days.

Climate change may bring stronger and more frequent atmospheric rivers, because the warmer the atmosphere is, the more water it can hold, says David Lavers, a meteorologist at Scripps who is not involved in the project.

“The more you know about how the atmosphere behaves,” he says, “the better position you’re in to prepare for extreme events.”

Read the full article on Nature website - Nature 517, 424–425 (22 January 2015) doi:10.1038/517424a

NASA UAVSAR: An airborne research team focuses on Andean volcanoes

This false-colour image of Peru's Ubinas volcano was acquired on April 14, 2014, by NASA's Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR). 

Located about 100 miles (160 kilometers) from the city of Arequipa, Ubinas is Peru's most active volcano. 

UAVSAR flew exactly the same flight path over Ubinas in 2013. 

By combining the images from the two years, researchers will produce detailed maps of surface motions that can improve models of volcanic deformation. 

Credit: NASA/JPL-Caltech

A NASA-developed airborne imager called a synthetic aperture radar took a detailed look at volcanoes in Central and South America during an Earth science study in late April and early May 2014.

The Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR), developed by NASA's Jet Propulsion Laboratory in Pasadena, California, was flown on NASA's C-20A.

The 29-day deployment ended May 6 when the aircraft returned to its base in Palmdale, California, after 19 flights totaling 97 hours in the air.

This is the second consecutive year the UAVSAR team has conducted a campaign to study sites in Central and South America.

Many of the flights imaged the Andean volcanic belt located in western South America.

"By combining images acquired in 2013 with the 2014 images, researchers will produce detailed surface motion measurements to improve volcanic deformation models," said Naiara Pinto, JPL's UAVSAR science coordinator.

NASA's C-20A features a high-precision autopilot designed and developed by engineers at NASA's Armstrong Flight Research Center, Edwards, California, allowing the aircraft to fly the same flight lines this spring as those flown in 2013 within 15 feet (4.5 meters) or closer.

With the autopilot engaged, the synthetic aperture radar is able to acquire repeat-pass data that can measure land-surface changes within fractions of an inch (centimeters).

NASA's C-20A aircraft crew preparing for flight from Tocumen International Airport in Panama City, Panama. 

The aircraft was deployed to Central and South America for a research study using JPL's UAVSAR airborne radar, located in an underbelly pod (note red cover). 

Credit: NASA/Armstrong Flight Research Center

In coordination with the volcano studies, the agency's C-20A gathered data over Amazonian forests in Peru, agricultural sites in Chile and glaciers on the Chilean/Argentinian border.

All of these research projects involve Latin American institutions, including universities and hazard monitoring agencies.

Robotic Bird Airplane Perching on a Human Hand - YouTube

The work by Aditya Paranjape, Joseph Kim, and Soon-Jo Chung at the Aerospace Robotics and Control Lab, University of Illinois at Urbana-Champaign.

Narration by Jenny Roderick at the University of Illinois at Urbana-Champaign.

By the virtue of their size and speed, birds are uniquely capable of efficient flight while flapping their wings and while gliding.

Researchers at the University of Illinois at Urbana-Champaign have duplicated the control functions that allow birds to successfully perform a soft landing—in this case, perching on a human hand.

“We believe we have the first demonstration of autonomous/robotic flight of a bird-like micro aerial vehicle (MAV) perching on a human hand,” stated Soon-Jo Chung, an assistant professor in the Department of Aerospace Engineering at Illinois.

Because the wings of ornithopters—birds or aircraft with flapping wings—are inherently capable of being reoriented, this capability can be used for controlling and maneuvering the aircraft in a gliding phase, thereby eliminating the need for additional traditional actuators. Gliding is an effective way to conserve energy while soaring, descending, and landing.

“The driving philosophy behind the work is that the maneuverability and control efficiency of avian flight can be replicated by applying their actuation and control principles to advanced MAVs designed on the size scale of small birds,” explained Aditya Paranjape, a postdoctoral scholar working on this project.

The result is based on his PhD thesis and a series of journal papers with Chung.

“We have developed an articulated-wing-based concept for an agile robotic aircraft inspired by birds,” Paranjape added. “Of all manoeuvers executed by flapping wing aircraft in a gliding phase, a perched landing is arguably the most challenging.”

Perching is routinely used by birds to land on objects such as tree branches, power wires, or building ledges. According to the researchers, there are two factors that make perching challenging to engineer: 1) the maneuver’s duration is very short, on the same order as the aircraft dynamics, and 2) a high level of position accuracy is required for a successful perched landing.

“Our aerial robot concept lacks a vertical tail for improved agility, similar to birds, which renders it dynamically unstable and exacerbates both of these factors,” Paranjape said. “We choose a perching maneuver to demonstrate the capabilities of our articulated-winged aircraft concept, novel guidance algorithms, and control design.

In particular, the ability to perform perched landings on a human hand endows our robot with the ability to operate around humans.”

A typical perching maneuver consists of two phases—a gliding phase to bring the bird to a suitable position with respect to the landing spot, and a rapid pitch up (usually to a post-stall angle of attack) accompanied by an instantaneous climb and rapid deceleration.

The researchers noted that the success of the maneuver can be severely impeded by the lateral-directional motion (yaw and roll), particularly when the perched landing has to be accomplished on a small surface such as an electric pole or a human palm.

In the absence of a vertical tail, wing articulation is a promising capability which can be used for both longitudinal and lateral-directional control.

Chung, who joined the Illinois’ faculty in 2009, brought with him a vision for developing aircraft that mimic the autonomy and agility of bats.

“There’s a lot to learn from bio systems,” Chung said. “Bats can fly with damaged wings. They are so agile and highly maneuverable; they can make rapid 180-degree turns autonomously and they can fly indoors without colliding with obstacles. These qualities are desirable for small aircraft that could be used in surveillance, particularly in urban settings where obstacles hamper movement and satellite control is blocked.”

The MAV project was funded by the Air Force Office of Scientific Research.


The technical details of this work can be found in the following papers.
A. Paranjape, J. Kim, and S.-J. Chung, "Closed-Loop Perching of Aerial Robots with Articulated Flapping Wings," IEEE Transactions on Robotics, under review, 2012. https://netfiles.uiuc.edu/sjchung/www/Paranjape12_perching_submitted.pdf

A. A. Paranjape, S.-J. Chung, H. H. Hilton, and A. Chakravarthy, "Dynamics and Performance of a Tailless MAV with Flexible Articulated Wings," AIAA Journal, vol. 50, no. 5, May 2012, pp. 1177-1188. https://netfiles.uiuc.edu/sjchung/www/AIAAJflexnew.pdf

A. A. Paranjape, S.-J. Chung, and M. S. Selig, "Flight Mechanics of a Tailless Articulated Wing Aircraft," Bioinspiration & Biomimetics, vol. 6, 026005, 2011. https://netfiles.uiuc.edu/sjchung/www/dihedral_final.pdf

Solar Impulse: Solar-powered plane makes airborne hop

The prototype of Solar Impulse, a pioneering Swiss bid to fly around the world on solar power, briefly took off for the first time on Thursday but under battery power, the organisers said.

The high tech single-seater with the wingspan of an Airbus A340 airliner (63.40 metres) made a controlled 400 metre (yard) flight about one metre above the runway at Duebendorf air base near the Swiss city of Zurich, said co-founders Bertrand Piccard and Andre Borschberg.

"A plane like that never flown before and it's extraordinary... because it's an area of flight that has been unexplored until now," Borschberg, chief executive of Solar Impulse, told AFP.

"It was very important to see if it would rise and what way we could keep it stable," he added.

Despite its wingspan, the aircraft only weighs 1,600 kilogrammes, about as much as a medium-sized car.

Although the prototype is fitted up for solar-powered flight, the four electric motors were powered by batteries for the occasion.

The prototype, which is slightly smaller than the craft that is expected to fly around the world, is primarily aimed at testing the cutting edge technology used to build and control the aircraft, and to fly through the night.

A first non-stop 36 hour flight through darkness is planned in Switzerland from spring 2010, with the prospect of a five stage flight around the world in 2012.