The Forecast for Forecasting Technology

 - December 30, 2008, 10:28 AM

Without the ability to understand and accurately forecast weather, NextGen technology won’t amount to much. For that reason, industry participants including Baron Services, NCAR and the FAA are not only working to integrate weather into the NextGen technology, but they are also working to improve forecasting techniques. One of the most significant advancements is the move from traditional Nexrad weather radars to dual-polarization Doppler radars.

In late 2007 the FAA awarded Baron Services and L-3 Communications a five-year, $43 million contract to design, develop and produce a system-wide upgrade of the 171 NWS, FAA and DOD Nexrad radars. Current radars provide storm location and intensity, as well as the movement of winds inside the storm–which is essential in forecasting tornados–but send out only a single horizontal beam to measure and analyze storm systems. The dual-polarization radar will send out two separate beams–in the horizontal and the vertical–giving forecasters the additional ability to measure the size, shape, orientation and state of precipitation in a storm system.

“In other words, we can actually tell what kind of precipitation type it is, whether it’s small raindrops, large raindrops, hail or snow,” Baron said. “It will enable meteorologists to see twice as much data.”

The new radars will also allow forecasters to see precisely where water droplets become frozen precipitation. “We’ll be able to see the layer of supercooled droplets,” Baron said. “This represents a substantial assistance to aviators because if you’re flying, you want to know exactly where you’re going to be running into icing.”
NCAR is responsible for most of the aviation weather information pilots obtain from the FAA and NWS. In fact, the majority of the work completed by the Research Applications Laboratory of NCAR is devoted to aviation weather. Research areas include in-flight icing; snowfall and freezing precipitation; convective storm nowcasting and forecasting; atmospheric turbulence; numerical weather prediction; remote sensing; precipitation physics; ceiling and visibility; oceanic weather; and verification methods.

The results of most of this research can be found–for practical purposes–on the aviation digital data service (ADDS) Web site and Experimental ADDS, which allows users to view and “test” new products. Once the FAA approves the products for operational use (generally as a supplemental weather product), they move to the operational ADDS Web site www.adds.aviationweather.noaa. gov; Experimental ADDS: www.weather.aero.

Among the new products on the Experimental ADDS Web site are various icing, turbulence and ceiling and visibility products that can be viewed using the Experimental ADDS flight path tool and the helicopter emergency medical services (HEMS) low-altitude flight tool.

The flight path tool displays icing, turbulence, ceiling, visibility, temperature, winds, humidity, radar and satellite information, as well as airmets, pireps, metars, and TAFs up to 44,000 feet msl. The tool lets users create vertical cross sections to view information horizontally and vertically, and the weather information is color coded for ease of use.

The HEMS tool provides ceiling, visibility, convection, icing and radar data from 500 feet agl to 5,000 feet agl. “We’re doing some really interesting things to support the helicopter EMS community,” said Marcia Politovich, deputy director of NCAR’s aviation application program and head of the icing research program. “They fly very low-altitude, short hops, so we built a tool that shows near-surface weather. It’s where we’re going with our tools for the future.”

The tool provides “nowcast” and very short-term forecast information. “The helicopter community told us they need to know what’s happening right now or within the next hour,” Politovich said. “Almost all the rescues are an hour or less.”
NCAR is also working to improve long-term ceiling and visibility forecasts, however. “That’s an active area of research here in the lab,” she said. “There have been several major EMS accidents in the last half year that have really spurred us on to make a better product for them. The accidents were caused by low ceilings, hitting obstacles and poor visibility.”

To date, the FAA has approved the use of the HEMS tool only for “no go” decisions, which is why it has not been moved from the Experimental ADDS Web site. “That’s an important legal distinction,” Politovich said. “A pilot can’t look at the tool and say, ‘I see a hole there, so I can go.’ He can look at it and say, ‘Yikes. This looks horrible. We cannot dispatch a helicopter to that location.’”

Another tool awaiting FAA approval is the national ceiling and visibility analysis (NCVA) tool, which is available in the “Metar” section of Experimental ADDS. “This is essentially a special interpolation, graphical representation of metar ceiling, visibility and flight information data,” Politovich said. “The information is available to you as a map with different Easter egg colors, and it represents our best estimate as to what the ceiling and visibility will be between two points, taking terrain into account.”

The NCVA tool also displays a “confidence” level along with the map view. “Usually it’s what we call ‘normal’ confidence, but there are some areas where we don’t have a lot of confidence,” she explained. “In the middle of Nevada, there aren’t any metar stations, so we would bring down the confidence a little bit to let people know that this is what we estimate but we don’t have much confidence in the data.”

Finally, the FAA and NOAA (NWS) are also involved in the research for new products through the FAA’s aviation weather research program, including the development and testing of aircraft-borne sensor systems that are installed on aircraft in the regional airline fleets and measure humidity, turbulence and icing in addition to wind and temperature. Two examples are the tropospheric airborne meteorological data reporting (Tamdar) system and the meteorological data collection and reporting system (MDCRS), which collect thousands of observations per day.

Another example is the advanced light detection and ranging (Lidar) system, which the FAA uses to measure wake turbulence. The Lidar uses laser energy to measure the amount and signature of turbulence in the air. “We use them to measure the behavior of wakes and wake conditions,” the FAA’s Steve Bradford explained. “Based on all the work we’ve done with Lidar, we know that when the wind is coming from a certain direction, wakes don’t transport from one runway to another.” The FAA also uses Lidar to measure the signature of new aircraft to determine what the wake requirements are behind certain types of aircraft.

Other agencies and private industry partners are working on various aviation weather research projects as well, but the overall focus of each project–no matter which agency or company is funding it–is to improve safety and efficiency. As Politovich explained, developing new products is often “a severe safety issue. We want to get it right. And if you can’t get it right, you want to have a conservative estimate,” she said.

“Weather is the key for us,” Bradford said. “The leading cause of delay is weather, and most of the en route problems are related to weather. We need efficiency in all weather conditions, so it’s important for us to do a better job with our programs.”