Airborne phased array radar could spur a “quantum leap” in hurricane forecasts

(NOAA)

Satellite view of Hurricane Iselle on August 4, 2014 in the eastern Pacific (NOAA)

Forecasts for the tracks of hurricanes have made huge strides over the past 15 years, improving by over 50 percent. But forecasts for the intensity of hurricanes have lagged, with only modest gains in accuracy seen very recently.

A new technology under development at the National Center for Atmospheric Research (NCAR), known as Airborne Phased Array Radar (APAR), could be a game-changer for improving forecasts for hurricane intensity and other types of severe weather, according to those familiar with the project.

A phased-array radar system consists of up to thousands of transmitters and receivers, spread across a rectangular plate. “Like many radar in one, phased array systems allow researchers to sample the atmosphere far more frequently,” says an NCAR fact sheet on the technology.

Scott Rayder, a senior advisor at NCAR, says APAR could provide unparalleled information on the three-dimensional structure of weather systems. “APAR’s like an MRI, whereas conventional radar is more like an X-ray,” Rayder says.

The proposed system would be mounted atop the fuselage and on the tail and nose of NSF/NCAR’s C-130 turboprop aircraft.

An APAR system would consist of four array antennas: 2 mounted on aircraft fuselage behind the rear doors, 1 on the tail and 1 on the nose. (NCAR)

An APAR system would consist of four array antennas: 2 mounted on aircraft fuselage behind the rear doors, 1 on the tail and 1 on the nose. (NCAR)

The system could be flown into a storm, sampling the environment and obtaining critical intelligence about its structure and health. This data could then be ingested into computer models which would provide potentially more realistic and accurate forecasts.

Fuqing Zhang, a professor of meteorology at Penn State University,  has documented recent improvements in hurricane intensity forecasts using data from the current generation of airborne Doppler radar (known as tail Doppler radars or TDRs). He thinks the APAR technology holds great promise.

“I believe the APAR will have the potential to benefit the hurricane intensity forecast in that it not only could be assimilated to improve the initial conditions of hurricane forecasts,” Zhang said in an email. “It can also help to verify the model in terms of hydrometers and microphysical processes, one of the key sources of model uncertainty in hurricane forecasts.”

Scientists will need to effectively make use of the data to make ground-breaking improvements, stresses Ryan Maue, a meteorologist and tropical weather expert at WeatherBell Analytics.

“[P]hased array radar may unlock discoveries or knock out old, broken theories,” Maue said. “I am in favor of investment that will lead to an incredible data resource — it is up to scientists to use the data for game-changing discoveries.”

Before APAR can be deployed operationally, several years of development and testing are needed.

“The major engineering hurdle is to miniaturize key radar components (antenna, transmitter, receiver) so that some 14,300 individual transmitter/receiver elements will fit on 4 flat plates mounted on the outside of the aircraft fuselage,” said Jim Moore, APAR project manager at NCAR.

Frank Marks, director of NOAA’s Hurricane Research Division, is an advocate for evaluating this cutting edge radar system.

“APAR is a new and potentially useful technology for hurricane forecast improvement and an observing technology that NOAA (and the hurricane research community) needs to evaluate,” Marks said in an email. “My push inside NOAA is to partner with NCAR to provide a means of testing APAR…”

NCAR’s Rayder, who says APAR data could spur a “quantum leap” in hurricane forecasts, says about $7.2 million in funding is needed for research, development and testing.

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